SECOND-ORDER DISCRIMINATION LEARNING IN HUMANS:

EFFECT OF PHYSICAL ARRANGEMENTS

WITH COMPARISON STIMULI

A Thesis Presented to the Faculty of California State University, Stanislaus

In Partial Fulfillment of the Requirements for the Degree of Master of Arts in Psychology

By Richard Radliff June 2014

CERTIFICATION OF APPROVAL

SECOND-ORDER DISCRIMINATION LEARNING IN HUMANS:

EFFECT OF PHYSICAL ARRANGEMENTS

WITH COMPARISON STIMULI

By Richard Radliff

Signed Certification of Approval Page is on file with the University Library

______Dr. William Potter Date Associate Professor of Psychology

______Dr. Bruce Hesse Date Professor of Psychology

______Dr. Carey Dempsey Date Assistant Professor of Psychology

ACKNOWLEDGEMENTS

First and foremost, I would like to thank my thesis chairperson, advisor and friend, Dr. Bill Potter for the many hours he spent assisting in the development of the software necessary to run this study, and for his encouragement when I had come very close to abandoning the project. Second, I would like to thank my research assistants, Lacee Ann Johnson, Omar Garcia, Sandra Oshana, and Zang Xiong.

Without their dedication, diligence, and help running participant sessions, the crucial process of collecting the data would not have been completed. Lastly, I would like to thank the CSU Stanislaus graduate committee for allowing me to carry on with the project after a long absence, during which completion of my thesis had become a faint hope.

iii TABLE OF CONTENTS PAGE Acknowledgements...... iii

List of Figures ...... v

Abstract...... vi

CHAPTER I. Introduction to the Study...... 1

Overview...... 1

II. Review of the Literature...... 3

Current Research...... 3 Symbolic Matching to Sample...... 5 Second-Order Conditional Discrimination ...... 8 Human Discrimination Research ...... 11 Purpose of Study...... 15

III. Methodology ...... 17

Participants...... 17 Apparatus ...... 17 Stimuli...... 18 Procedure ...... 21

IV. Results ...... 30

First-order Discrimination Training ...... 30 Second-Order Baseline ...... 33 Second-Order Discrimination Training ...... 35

V. Discussion and Summary ...... 41

Limitations ...... 48 Future Research ...... 50 Summary...... 51

References...... 54

iv LIST OF FIGURES

FIGURE PAGE

1. Mixed element phase configuration...... 25

2. Second-order partitioned configurations...... 27

3. Second-order integrated configuration ...... 28

4. First-order trials to mastery...... 30

5. Baseline results by condition for participants 1, 2, & 3...... 32

6. Baseline results by condition for participants 4, 5, & 6...... 33

7. Participant 1 and 2 second-order training ...... 35

8. Participant 3 and 4 second-order training ...... 36

9. Participant 5 and 6 second-order training ...... 37

10. Integrated and partitioned comparison configurations ...... 44

v ABSTRACT

Conditional discrimination learning in animals has been the source of research for many decades. However, primary factors involving human discrimination learning remain obscure. It is the goal of the current research to investigate the effect physical properties of comparison stimuli have on the learning process in humans. This study extends to humans a line of research that utilized pigeons in second-order discrimination training, conducted on the California State University, Stanislaus campus. Six undergraduate students were recruited to test the effects of second-order comparison arrangements under two conditions. The integrated (superimposed) and partitioned (non-superimposed) conditions were presented after first-order training with 3 elements (color, shape, and pattern). As in the prior research, a symbolic- match-to-sample methodology is used to train, and test, participants in first and second-order conditional discriminations. Results from second-order trials are inconclusive, but demonstrate a pattern of responding which is affected by the comparison stimuli conditions. All participants demonstrated generalization of second-order conditional discrimination from first-order training. Results of first- order training confirmed the results of animal research, where significantly more trials were required to attain mastery with pattern comparisons.

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CHAPTER I

INTRODUCTION TO THE STUDY

Overview

The capacity to adapt to environmental changes, or learn, is a fundamental characteristic of all organisms. Skinner (1953) proposed that learning was a

“reassortment of responses in a complex situation” (p. 65). He used this definition in describing principles supporting operant behavior. The underlying suggestion refers to an inherent flexibility to operant behavior. Because operant behavior affects the environment in a way that produces a particular effect, consequence, or reinforcement, the operant is characterized by the attributes upon which reinforcement is contingent (Skinner, 1953). However, the attributes of a behavior can vary and/or adapt. The variability of behavior may lead to alternate reinforcing consequences, further refining operant behavior. Adaptation occurs as a result of this refinement when more effective forms of behavior replace older ones (Skinner,

1953). Changes in the environment also produce changes in our behavior.

Accordingly, operants are selected by the consequences (Pierce and Cheney, 2004).

This relation between behavioral variability and contingent consequences comprise what may be generically defined as learning. That is, behavior in organisms is shaped, to a greater or lesser degree, by conditions that produce reinforcement in a variety of situations and environments. Examining conditions under which behavioral

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adaptation is promoted or inhibited is fundamental to understanding behavior and learning.

Operant behavior can be described without mention of antecedent conditions.

However, to understand probabilities of operant behavior requires an understanding of functional connections to stimuli which evoke such behavior (Skinner, 1953).

Skinner offers the example of a pigeon, where the presence of a light (stimulus) sets the occasion for a response (stretching the neck) which is followed by reinforcement.

In the presence of the light, the pigeon’s neck-stretching is more probable because the light occasions the availability of reinforcement. The behavior is not emitted spontaneously in the presence of the light. The pigeon’s behavior develops from repeated exposure to the antecedent stimulus and subsequent availability of reinforcement. Skinner describes the process through which this occurs as discrimination. This example also describes the basis of the three-term or operant contingency, stimulus-response-consequence (S → R → S r).

The process of discrimination is fundamental to most human behaviors. The principle of discrimination suggests that we will respond differentially to dissimilar situations if behavior is reinforced in one situation not another (Pierce and Cheney,

2004). It is through the process of discrimination, and the selection of operant behavior by consequence, that complex behaviors develop. Verbal behavior is a prime example of a complex behavior that is shaped by these principles. As Skinner

(1957) notes, the selection of verbal behavior by contingent social consequences is a significant process fundamental to human communication.

CHAPTER II

REVIEW OF THE LITERATURE

Current Research

In order to understand complex behaviors it is essential to examine the most fundamental aspects first. A review of behavior research reveals a substantial amount of material involving discrimination behavior (e.g., Blough, 1959; Carter and Werner,

1978; Cowles, 1941; Cumming & Berryman, 1961; Harlow, 1950; Mader & Price,

1980; Pepperberg, 1990; Sidman, 1986; Vonk & McDonald, 2002). The majority of research which addresses discrimination learning has been conducted using non- human subjects. For example, Harlow (1950) conducted research using 10 rhesus monkeys to examine factors which produced errors in discrimination learning.

Harlow utilized the Wisconsin general test apparatus, which was for many years the apparatus of choice for studies of discrimination learning (Rollin, Shepp, & Thaller,

1963). Harlow’s monkeys were given a basic two choice sample. Placed beneath one sample was a food reinforcer. Selecting the sample which masked the reinforcer resulted in reinforcement. Harlow concluded that error frequencies were not found to be associated to the amount of food consumed or the number of preceding trials during the course of a day’s session.

Second, and more importantly, results demonstrated that in the early stages of discrimination learning, the monkeys learned discriminations gradually. On later discrimination trials, the monkeys learned most of the discriminations in a single trial

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(Harlow, 1950). Harlow suggested the reason for increased rates of acquisition was best explained in the context of the subjects’ past experience with particular learning trials. Harlow states, “In the solution of a long series of discrimination problems, monkeys showed progressive change from gradual learning to one-trial learning” (p.

37).

Research which incorporates the process of discrimination in humans has largely been conducted in the areas of category and concept formation, stimulus equivalence and contextual stimulus control (Zentall 2002). Studies which examine fundamental conditions under which discrimination learning occurs in humans are less numerous. Zentall offers some insight as to the reason for the disparity. He suggests that categorization is readily conceived in the same terms as stimulus discrimination when stimuli vary along simple dimensions. This idea is illustrated in research conducted by Kendler and Vineberg (1954). Their study sought to determine the effect that the learning of simple concepts on the learning of compound concepts, which involved combinations of simple concepts. Kendler and Vineberg state;

An example of a simple concept would require sorting a series of cards by the

color of the figures on them. Another simple concept would require Ss to sort

the cards according to the size of figures. A compound concept would involve

sorting on the basis of both size and color. (p. 252)

Kendler and Vineberg (1954) were examining concept acquisition based on simple discriminations. In fact, the example of “compound concept” offered by Kendler and

Vineberg defines second-order discrimination discussed herein. It is important to note

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the researchers’ early focus on concept development rather than discrimination learning, even though the study was fundamentally based on discrimination processes.

The current study focuses on discrimination learning, and seeks to supplement the current body of research through examination of conditions which affect the emergence of conditional discrimination in humans. Additionally, this study extends to humans, research being conducted on pigeons at California State University

Stanislaus, which examines the acquisition of second-order conditional discriminations utilizing a match-to-sample methodology (Duroy, 2005; Redner,

2009).

Symbolic Matching to Sample

The current study utilizes a variation of the match-to-sample (MTS) procedure where sample and comparison stimuli are arbitrarily defined. If a predetermined arbitrary stimulus is presented as the sample, the correct comparison could involve selecting a comparison of a particular color, shape, or pattern. This is known as symbolic matching (Carter & Werner, 1978), or as used herein symbolic-match-to- sample (SMTS) (McKay, 1991). SMTS has only two requirements 1) the sample and the designated comparison are not physically identical, and 2) there is only one correct comparison for each sample.

SMTS is an effective methodology for examining the effect that formal relations between sample and comparison stimuli may have on acquisition of conditional discrimination behavior (McKay, 1991). Arbitrary conditional

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discriminations give rise to novel relations (Pilgrim, Jackson, & Galizio, 2000). This is of particular interest in studies involving human participants due to our formative capacities to develop such novel and complex relations. These novel relations are a point of departure from discrimination learning to research in the areas of categorization, concept development, and contextual control.

An investigation of discrimination learning in normally developing children which utilized the SMTS procedure was conducted by Pilgrim et al. (2000). They found that studies involving children have revealed mixed findings with respect to the acquisition of SMTS performance. Pilgrim et al. noted that training procedures and experimental conditions varied widely and that the effects of procedural variables on acquisition remain undetermined. The primary conclusion drawn from their study was that SMTS is not readily acquired by young normally developing children in the absence of special training procedures. Pilgrim et al. state, “What remains to be determined is the basis for the difficulties in learning that were observed here. After all, non-humans acquire arbitrary MTS performances with out heroic interventions”

(p. 190). In order to shed light on the difficulties that they describe, a more comprehensive examination of basal factors which foster the acquisition of SMTS is needed.

Experimentation with pigeons has provided much information in regards to basal factors. Two broad categories of factors have been examined, procedural variables and physical properties of stimuli. For example, Carter and Eckerman

(1975) examined the acquisition and performance of pigeons on SMTS tasks. The

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Pigeons were exposed to a variation of the 3-key MTS procedure described by

Cummins and Berryman (1961). Four stimuli were used as samples and comparisons

(red or green and vertical or horizontal line). Keys were configured to display either of two samples and two comparisons. There were four groups of five birds, two groups were exposed to SMTS (line to color matching or color to line matching), and two groups were exposed to MTS (color matching or line matching). It was found that the SMTS task was not a more difficult task than the matching to sample task.

Acquisition was most affected by the physical properties of the stimuli. Color matching was learned most quickly, and line matching was the last to be acquired. In the two groups where lines were used as sample stimuli, they found that acquisition was slower, regardless of whether the comparison stimuli were colors or lines (Carter

& Eckerman).

Procedural factors within MTS designs, which affect discrimination learning, have been studied extensively in pigeons (Berryman, Cohen, Cumming, & Johnson,

1965; Blough, 1959; Duroy, 2005; Roberts, 1972; Wyckoff, 1952). Similar studies have been conducted with humans (e.g., Jordan, Pilgrim, & Galizio, 2001; Pilgrim et al., 2000; Saunders & Spradlin, 1990; Williams, Johnston, & Saunders, 2006).

Procedural variations that have been examined include variations of reinforcement schedules, inter-trial interval duration, observing responses, stimulus positions, number if stimuli, timeout intervals, correction procedures, and delayed reinforcement (MacKay, 1991; Duroy, 2005). Since procedural variables within this study were not points of examination, a comprehensive discussion was not presented.

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Second-Order Conditional Discrimination

The MTS procedures described to this point are principally first-order conditional discriminations. In first-order discriminations the operant contingency is itself placed under the control of additional conditional stimulus (Mackay, 1991). One of the earliest examples of conditional stimulus control is Lashley’s 1938 experiment involving rats. In this experiment he presented a simple two choice sample that consisted of equilateral triangles. One triangle was presented upright and the other inverted. The rats responded by jumping toward the correct sample. The correct sample was determined by the color of the background upon which the triangles were presented. A black background indicated that the upright triangle was the correct sample, and a horizontally stripped background indicated the inverted triangle as correct.

The current research investigates second-order conditional discrimination.

Second-order conditional discrimination occurs when the role of the SD is dependent

D D2 D1 R upon a second S (e.g., S : S : S → R → S ). For example, in a SMTS task a participant is presented with a sample stimulus and several comparison stimuli.

Correct responding to the comparison stimuli is conditional on the sample, as in

Lashley’s 1938 experiment. If an additional sample stimulus is presented, the MTS task becomes a second-order discrimination. Under this arrangement two unique samples are presented, each associated some aspect of the correct comparison (e.g., color and shape). Responding to the correct comparison (e.g., red square) is now conditional on the both samples. If SD1 controls responding to the color red, and

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several comparisons are red, and SD2 controls responding to the shape square, then only the red-square comparison is correct.

As noted, the majority of second-order discrimination research has been conducted with non-humans (e.g., Duroy, 2005; Harlow, 1943, 1950; Lashley, 1938;

Schusterman & Krieger, 1986; Spaet & Harlow, 1943; Young & Harlow, 1943a,

1943b). These studies have included pigeons, rhesus monkeys, rats, and California sea lions. Some of the most notable studies have been conducted by Pepperberg

(1990).

Prior to Pepperberg’s work, second-order conditional discrimination behavior had only been demonstrated in primates and mammals (Pepperberg, 1990). However,

Pepperberg was able to demonstrate the behavior in an African gray parrot. The parrot, named Alex, had been trained in identifying multiple characteristics of objects.

Pepperberg describes Alex’s ability:

Alex could produce vocal (English) labels for seven colors (green, rose

[red], blue, yellow, gray, purple, and orange), several shapes (2-, 3-, 4-

, 5- and 6- corner, respectively, for football-shaped, triangular, square,

pentagonal, and hexagonal forms), and seven materials (cork, wood,

hide [rawhide], paper, chalk, wool, and rock [play-doh forms] and

could label various items of metal (key, chain, grate, tray, truck [toy

cars]), wood (peg wood and block), and plastic or paper (cup and box;

Pepperberg, 1978b, in press-b). (p. 43)

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In combination, Alex was able to identify more than 100 objects (Pepperberg,

1990). In a demonstration of second-order conditional discrimination, Alex would be presented with one of four vocal questions in regard to any object within the assortment of seven exemplars. The question presented to Alex would take one of the following forms, “What color is [designated object]?”, “What shape is [designated object]?”, “What object is [designated color]?”, or “What object is [designated shape]?” (p. 43). Alex would then provide a vocal response to the question. In order to respond correctly, it was necessary for Alex to respond to two elements of the question regarding shape, color, or material. For example, a response to “What color is wood?” required a discrimination of material ( SD1 ) and then color ( SD2 ), thus demonstrating a second-order conditional discrimination.

Pepperberg (1990) reports that Alex’s first response was correct on 39 of 48 trials (81.3%). For all presentations his score was 48 of 57 or 84.2% accuracy. Scores for both types of questions in regard to color were 75.0% on first trial presentations, and 80.0% on all trials. In regards to shape, Alex attained 87.5% on first trials, and

88.9% on all trials.

Hesse and Potter (2004) offered a cautionary note when interpreting the results of Pepperberg’s remarkable achievement with Alex. In their review of

Pepperberg’s book The Alex Studies they comment that Pepperberg confined her scoring of incorrect responses to only those response forms relative to the task at hand. Alternate responses were not considered incorrect. For example, if only four response forms (e.g., paper, key, wood, or hide) were relative to the question

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presented Alex, “only those incorrect responses that were one of the 4 response forms being tested” were counted (Hesse & Potter, p. 146). Despite this, Alex clearly demonstrated that second-order conditional discrimination in birds was possible.

Alex’s execution of second-order conditional discriminations is a significant milestone in discrimination research. It is equally noteworthy that Alex’s performance came in the form of vocal responses, an ability only shared with humans.

Human Discrimination Research

Along with the shift from basic discrimination research to concept learning, human research in the area of second-order conditional discrimination has diverged from the line of inquiry embraced by animal researchers. There have been many studies which examined the acquisition of second-order conditional discrimination with human participants (e.g., Bush, Sidman, & De Rose, 1989; Gatch & Osborne,

1989; Kennedy & Laitinen, 1988; Lynch & Green, 1991; Perez-Gonzalez &

Martinez, 2007; Perez-Gonzalez & Serna, 2003; Perez-Gonzalez, Spradlin, &

Saunders, 2000; Ribes, Moreno & Martinez, 1998; Serna & Perez-Gonzalez, 2003;

Wulfert & Hayes, 1988). These studies are primarily a line of second-order conditional discrimination research which investigates contextual control of conditional stimulus relations, or stimulus equivalence relations. It is not within the scope of this study, nor is it entirely relevant, to comprehensively cover contextual control or stimulus equivalence research. However, this line of research represents the

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bulk of second-order conditional discrimination research in humans, and contained within it may be clues to more elementary questions regarding acquisition.

A review of second-order conditional discrimination research with humans indicates a shift of researchers’ interest away from research on conditions under which second-order conditional discrimination behavior is acquired. The shift may have also obscured the necessity for such basic research. The extension of second- order conditional discrimination to humans, and subsequent shift to a contextual control paradigm (e.g., Bush et al., 1989; Lynch & Green, 1991; Perez-Gonzales &

Martinez, 2007) also resulted in a revision of terminology that somewhat obfuscates more basic second-order research. For example, Lynch and Green (1991) state, “To conduct functional analyses of stimulus equivalences in language, then, it is important to understand how second-order conditional stimulus control is acquired by contextual stimuli (Bush et al., 1989; Sidman, 1986)” (p. 140). The term “contextual stimuli” is used in this statement to denote the second-order stimuli. The term may offer some clarification for researchers in which stimulus equivalence relations are suggested as a factor in explaining the acquisition of language (Lynch and Green,

1991), but is unnecessary in second-order discrimination research that examines conditions which contribute to acquisition of discrimination behavior.

The distinction these researchers make is best exemplified by Perez-Gonzalez and Martinez (2007), “Contextual stimuli should exert functions at a higher level than the functions exerted by the samples. Therefore, a procedure that serves to teach second-order conditional discriminations does not guarantee that the putative

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contextual stimuli be true contextual stimuli” (p. 119). This statement highlights the added complexity the terminology presents for fundamental second-order discrimination research. In addition, what constitutes second-order stimuli is also drawn into question.

The question of what constitutes true second-order stimuli is explained by two primary theories for second-order discrimination that stimulus-equivalence researchers have put forth. Bush et al. (1989) suggest contextual control results when contextual stimuli function as second-order stimuli, when explicitly arranged contingencies place second-order stimuli in control of the first-order conditional discriminations. This account is described in the sample-comparison relation example, X1:A1 →B1 or X2:A1 →B2. For example, in the presence of contextual stimuli X1, in a sample-comparison relation where A1 is the sample, and the comparisons are B1 and B2, B1 is selected. In the presence of the contextual stimuli

X2, the alternate comparison B2 is selected, thus controlling the sample-comparison relation.

The alternative interpretation of second-order control suggests that second- order stimuli enter into stimulus compounds with the first-order stimuli (Bush et al.,

1989). The implication is that subjects are making only first-order discriminations, albeit with more complex stimuli (e.g., X1/A1 = B1 or X2/A1 = B2). Lynch and

Green (1991) suggest that “True second-order conditional control is inferred when contextual stimuli function independently of the stimuli with which they were presented in training” (p. 152). If we were to apply the criteria suggested by Lynch

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and Green to our example of second-order SMTS task, it may not qualify as second- order conditional control. Rather, the two sample stimuli might be considered a compound stimulus, and the behavior a first-order discrimination. It is important to recognize that the distinction here is one of covert processes and not observable physical arrangements of stimuli.

The study of conditions under which a second-order conditional discrimination arises does not benefit from the application of these theories. This is exemplified in research with three university students conducted by Bush et al.

(1989). In this study “sample (an A stimulus), the tone (high or low) determined the comparison (one of the B stimuli) that the subject was to select” (p. 41). The low tone and a high tone were used as the putative contextual stimuli (second-order stimuli) which were trained to exert control over the conditional stimulus relations. The researchers’ subjects acquired second-order conditional discrimination behavior, but

Bush et al. conclude the following:

On the face of it, the tones seemed to be controlling equivalence relations

even between visual stimuli that had never been presented with tones while

conditional discriminations were being explicitly taught. If this were correct,

true second-order conditional control would have been demonstrated. The

reason for the tentative nature of this conclusion lies in the subject's

descriptions of the rules he was following during probes for emergent

conditional discriminations. (p. 42)

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Other researchers have also reported similar conclusions (e.g., Gatch & Osborne,

1989; Kennedy & Laitinen, 1988; Wulfert & Hayes, 1988). The underlying significance is reflected not in the experimental definitions of what “true contextual stimuli” are, but in the factors under which the subject came to learn the discriminations. This includes the covert verbal behavior which influenced acquisition. Bush et al. (1989) describe the behavior of their subject, “The subject's performance can be described as a chain in which his verbal rule, interacting with the experimental stimuli, acted as a complex set of discriminative stimuli (Skinner, 1969, pp. 122, 142-148) to determine his final choices” (p. 43).

If the definition of second-order discrimination is dependent on covert process by which a subject comes to perform second-order discriminations, then a more fundamental question should address the conditions by which participants develop

“rules” for performing such behavior. The conclusions drawn suggest that until a more accurate tool is developed for establishing the nature of covert processes employed by participants, definitions of what constitutes second-order discrimination will remain ambiguous. The approach of the current study is to define second-order stimuli and second-order discrimination based on physical arrangements of the stimuli, rather than underlying covert processes.

Purpose of Study

As stated, the current study extends to humans, research conducted on pigeons by Duroy (2005) and Redner (2009), which examined the acquisition of second-order conditional discrimination behavior. In this study a SMTS task was used to examine

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the acquisition of second-order conditional discriminations by college students.

Sample stimuli were arbitrarily selected, and each matched to a unique variation of the color, shape, or pattern. The primary objective of the study was to determine the effect of comparison stimuli arrangements on the acquisition of second-order conditional discrimination performance with human participants.

Two terms used here describe the comparison stimulus arrangements, integrated and partitioned . In an integrated arrangement, a comparison stimulus was presented along two or three dimensions, and superimposed upon each other (e.g., a red stripped triangle). In the partitioned arrangement each dimension of the comparison is presented in its unique form, apart from the other dimensions, but immediately adjacent to each other (e.g., red dot, stripes, and triangle). This study examined whether acquisition of second-order discriminations was faster with integrated or partitioned comparison stimuli.

CHAPTER III

METHODOLOGY

Participants

Prospective participants were asked to answer a brief questionnaire. Included were questions regarding prior experimental participation and familiarity with the

Cherokee language alphabet. Any prior exposure to the Cherokee language was regarded as cause for exclusion from the study. Six undergraduate students, five female and one male, were recruited for participation. None of the students had prior second-order conditional discrimination experimental histories. Once criteria for participation were met, each participant was briefed on the conditions of the experiment, requirements for compensation, and presented with an informed consent form for review and signature.

Participants were compensated for their participation based on the number of experimental phases completed. Tutorial and baseline phases were excluded. Seven training phases were progressively compensated, beginning with 5 dollars for the first phase and 2 dollars additional for each subsequent phase. Upon completion of all phases, a bonus of 8 dollars was added to the last phase. Participants could then earn a maximum of 85 dollars for participation.

Apparatus

All experimental sessions were conducted on the campus of CSU Stanislaus in an available research room. Participants were provided a laptop computer during each

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session which managed stimulus presentation and data collection. Experimental sessions were conducted at various times each day depending on the participants’ availability. Each participant was seated in front of the laptop computer running

Revolution software, version 5.4. The software controlled the presentation, selection, and order of sample and comparison stimuli displayed during trials. Responses to stimulus presentations during all trials were made through the laptop via a computer mouse interface, and recorded by the software.

Stimuli

Sample stimuli

Eighteen arbitrarily selected sample stimuli were comprised of single element forms. The sample stimuli were modeled on Cherokee alphabet characters (see Table

1). Characters appeared as white figures on a black background. All sample stimuli presented on the laptop display were approximately 2 in 2 (50.8 mm 2). Each unique sample stimulus correlated to a unique variant of the comparison stimuli (e.g., red, square, or checkerboard). One or two sample stimuli appeared in the center of the laptop screen the screen (see Figures 1 & 2).

Comparison stimuli

During first-order trials each comparison stimulus presented was paired with one sample stimulus (see Table 1). Comparison stimuli were based on previous works by Duroy (2005) and Redner (2009). Comparison stimuli were based on three primary elements, colors, patterns and shapes, in single-element or multi-element arrangements.

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Table 1

First-order Stimuli and Pairings by Element

Color Pattern Shape

Sample Comparison Sample Comparison Sample Comparison

(Blue) (Check) (Circle) A G M

(Green) (Melon) (Posy) B H N

(Orange) (weave) (Heart) C I O

(Purple) (Marble) (Hex) D J P

(Red) (Tie-dye) (Star) E K Q

(Yellow) (Wave) (Triangle) F L R

Six variations of each element were created, for a total 18 unique comparison stimuli which resulted in 18 sample-comparison pairings. Variations of color were red, green, blue, yellow, orange, and purple; variations of pattern included check,

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melon, weave, marble, tie-dye, and wave; variations of shape included circle, posy, heart, hex, star, and triangle (see Table 1 for names of sample stimuli). Comparison stimuli were produced using Adobe Photoshop™ software and were also 2 in 2 (50.8 mm 2).

During trials, comparison stimuli were randomly ordered and appeared adjacent to the sample stimuli in vertical columns of three. (see Figures 1, 2, & 3).

Each comparison stimulus displayed was a unique variation (e.g., blue, triangle, marble, orange, circle, and checkers). The background screen color on all trials was charcoal grey.

Second-order comparison stimuli were composed of the element pairs color and pattern (CP), color and shape (CS), or pattern and shape (PS). For each comparison stimulus two unique variations were randomly selected, one variant from each element, and presented in pairs (e.g., red and square) to form compound comparisons. During second-order baseline and training phases, two configuration schemes were used to display comparison stimuli. These configurations were identified as integrated or partitioned . As shown in Figure 2, the dimensions of the partitioned comparison stimuli were displayed as a cohesive group but not superimposed, whereas the dimensions of integrated stimuli were superimposed (see

Figure 3).

To augment the association of elements in partitioned comparisons, all partitioned stimuli were presented with the addition of a low contrast gray box which outlined the elements of each individual comparison stimuli. No outline box was

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presented with integrated comparison stimuli. Second-order comparison stimuli were displayed (see Figures 2 & 3) in a manner identical to the arrangement of first-order comparison stimuli (see Figure 1).

To create two second-order stimulus configurations from a given pair of elements, three variants from each of the two first-order comparison elements were randomly assigned to either the partitioned or the integrated configuration with the

Revolution software. Once assignments were made, variants only appeared in partitioned or integrated arrangements, not both. Subsequently, for each pair of elements CS, CP, or PS, when the variants of each element were assigned as partitioned or integrated, nine integrated and nine partitioned comparison stimuli were available for a total of 18 compound comparisons. All combinations of integrated and partitioned stimuli across CS, CP, and PS, equaled 54 unique second- order comparison stimuli.

Procedure

At the initiation of the study, each participant received instruction on the use of the laptop and input device from the researcher. Once instruction was completed a tutorial session commenced. Participants were given the tutorial once, prior to commencement of the first session beginning the first-order training. The tutorial included stimuli not used in subsequent first-order and second-order trials, but was procedurally similar. Additionally, participants’ sessions were limited to minimize fatigue. Participants were limited to either a two hour session with one 10 minute break after the first hour, or the completion of training in first-and second-order

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discriminations, whichever came first. Prior to the start of training sessions, a participant number was assigned to each participant and used to identify them throughout the study. All reference to stimuli assignments, order of training phases, and recording of data was identified by the participant number.

Tutorial

The tutorial session was initiated when the research assistant opened the tutorial program. The screen displayed a window that contained a brief paragraph with instructions. In the same window, below the instructions, was a single sample stimulus. The instructions directed the participant to make a single observing response to the sample stimulus that appeared in the center of the screen. A single click via the mouse with the pointer over the sample resulted in simultaneous presentation of the comparison stimuli. Comparison stimuli would not appear until an observing response was made. Six comparison stimuli appeared in two vertical columns on each side of the sample in random order. A single click to the correct comparison resulted in an audible reinforcer (e.g., “good job”). Incorrect responses during the tutorial resulted in an audible prompt (e.g., “try again”). After each response to a comparison a “reset” button was selected by the research assistant which repeated the trial. Trials were repeated until the participant was comfortable with the procedure.

First-order conditional discrimination training

First-order training was divided into three phases, each corresponding to one of the three elements color, shape, or pattern. The order in which training phases were

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presented to each participant was randomly determined prior to the start of training.

During each phase only the six sample and comparison stimuli relevant to that particular element were presented . Each participant was trained in each of the three phases separately. Mastery of one phase was required before a new phase began.

First-order SMTS training commenced with the presentation of one sample stimulus, and following an observing response, six comparison stimuli were simultaneously presented along with the sample. Comparison stimuli were again randomly ordered in two vertical rows, three to each side, and adjacent to the sample as shown in Figure 1. The six sample stimuli were presented in random order without replacement in blocks of six trials. No sample was presented in two consecutive trials with the exception of remedial trials. During the first two blocks (12 trials) the correct comparison was highlighted in each trial with a magenta border. An audible reinforcer for each correct response was provided on a FR1 schedule during training phases. Training trials were always presented with a limited hold of 20 s in place. If no response was made to comparison stimuli during the limited hold, the trial ended and a new trial began. A non-response (timeout) was treated as incorrect and a new trial was presented.

Following the initial 12 trials, participants were required to respond to comparison stimuli without prompting. Selection of the correct comparison completed a trial and a new trial was presented following an ITI of 2 seconds. In all training phases of the study incorrect responses resulted in remedial trials. Remedial trials duplicated the previous trial with the highlight box present, prompting the

24

correct response. A correct response during the remedial trial resulted in presentation of a new trial after an ITI. Correct responses were recorded only when participants selected the correct comparison on the first presentation of a new trial. Remedial trials were recorded but did not count toward mastery criteria. Participants received reinforcement for all correct responses including remedial trials.

Criteria for completing a phase of training required four consecutive blocks with 22 correct responses in 24 first trial presentations (92% correct). The software recorded all responses in each block until participants had achieved a response performance of 92% correct in 24 consecutive trials. Once participants achieved the criteria for the current phase the program terminated the phase. The next phase was then loaded by the researcher. All subsequent phases proceeded in the same manner until participants reached the prescribed criteria in all phases of color, shape and pattern.

Mixed element phase. Following first-order training phases for each element a mixed phase was initiated. The mixed phase was presented as precursor to second- order trials that would include mixed element comparisons. The procedure during the mixed phase was identical to previous phases, but incorporated variations of each element. Only two variations from each element were randomly selected and presented as a set of six (e.g., two shapes, two colors, and two patterns). Samples and comparisons were selected from the 18 pairs available. Each sample appeared once in random order without replacement, and no sample appeared in successive trials. Six comparison stimuli were again displayed adjacent to the sample. Comparison stimuli

25

Figure 1. First-order, mixed phase configuration.

were randomly arranged trial-to-trial with two variations from each of the three elements (see Figure 1).

The mixed phase proceeded as in previous training phases, including remedial trials. Criterion for mastery of the mixed phase was identical to the previous first- order phases. The mixed training phase concluded when the prescribed mastery criteria was achieved.

Second-order baseline

Second-order baseline trials commenced upon completion of the first-order mixed phase. The second-order baseline session was implemented to determine the level of acquisition of second-order discrimination behavior from first-order discrimination training. For each participant, comparison stimuli were assigned to

26

either the integrated or the partitioned condition prior to the start of training. During the second-order baseline phase 54 trials were presented. Twenty-seven trials presented integrated comparisons, and 27 presented partitioned comparisons.

Integrated and partitioned comparison stimuli were presented separately trial-to-trial and never together in the same trial (see Figures 2 &3).

Each sample stimulus only appeared once with the order of presentation randomly selected without replacement. Six comparisons were presented in each trial with one correct comparison and five alternate comparisons randomly selected from either the integrated or partitioned sets. Participants received no reinforcement during the baseline phase, and no remedial trials were presented for incorrect responses.

Responses for all trials were recorded as either correct or incorrect.

Second-order discrimination training

Second-order discrimination training commenced following completion of the baseline phase. The procedure for second-order training duplicated the procedure of first-order discrimination training with the addition of a second sample stimulus and the compound comparison stimuli. Participants were again trained in three phases, and each phase was identified by the pairing of elements as CS, PS, or CP. The order in which phases were trained was again randomly assigned each participant. The prior assignment of comparison stimuli to integrated or partitioned configurations, from the second-order baseline phase, was maintained for all second-order training phases. All resultant pairings of element variants were trained in each phase. For example, during

27

Figure 2. Second-order partitioned configurations. the CS phase nine integrated configurations and nine partitioned configurations of color and shape were trained.

For each trial, sample stimuli were randomly selected without replacement, thus partitioned and integrated trials were also randomly ordered. Six comparisons were again presented in each trial, with one correct comparison. Alternate comparison stimuli were randomly selected from all 54 available second-order comparisons, regardless of the phase being trained. Integrated and partitioned comparisons never appeared in the same trial together. For example, a phase in which CP stimuli were being trained may include alternate comparisons from CS and PS sets. Trials were presented in blocks of 18, and during the first set of 18 trials the correct comparison was again highlighted in each trial.

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Figure 3. Second-order integrated configuration.

Mastery for each phase was attained when participants responded correctly on

17 of 18 (94%) first trial presentations (two consecutive blocks) for the integrated or partitioned configurations. Following mastery of the first condition, an additional 18 trials would be presented if mastery of the second condition was not attained. The phase would end if either mastery was attained for the second condition or 18 additional trials were completed. Following mastery of one phase, another phase of untrained element combinations was initiated (e.g. CS after PS). Demonstrated mastery in all three phases concluded the second-order training. Participants were then instructed to complete a post study questionnaire. The post study questionnaire included questions regarding (a) rules they may have developed to achieve conditional discriminations, (b) criteria upon which selections were based, and (c) the

29

nature of any difficulties they experienced during training. The purpose of the assessment was to illuminate covert behavior (i.e., verbal behavior) that influenced the process of learning. The primary goal was to provide clues to future researchers interested in designing research to investigate such behavior.

Dependent variable

The study presented participants’ with a multi-element design. A participant’s performance was expressed as the total number of trials (i.e., trials including correct, incorrect, remedial, and timeouts responses) needed to reach mastery criteria for each phase or condition.

CHAPTER IV

RESULTS

First-order Discrimination Training

Values from all categories were used in calculating the total number of trials to reach mastery for each element. All incorrect responses were followed by a prompted correction trial and so occurred with the same frequency and are shown in associated figures. Preliminary prompted trails during training phases are also shown.

The results of first-order training phases for all participants are shown in Figure 4.

Value labels for correction trials and timeouts were omitted from the graphs for clarity. No statistical analysis was conducted.

Participant 1 achieved mastery of colors with 36 trials which included 23 correct responses and 1 timeout; mastery of shapes was achieved after 37 trials and included 23 correct responses and 1 incorrect response; mastery of patterns required

52 trials with 30 correct responses and 5 incorrect responses.

Participant 2 achieved mastery of colors after 36 trials without error; mastery of shapes was attained after a total of 52 trials, including 30 correct responses and 5 incorrect responses; mastery of patterns was achieved in 36 trials without error.

Participant 3 attained mastery of colors following 52 trials with 30 correct responses and 5 incorrect responses; shapes were mastered following 38 trials that included 22 correct and 2 incorrect responses; patterns required 121 trials including

47 correct responses as well as 31 incorrect responses.

30 31

1st order, Trials to mastery 121 120

100

Timeout

80 31 Correction

Trials 60 52 52 52 Error

37 5 5 5 38 Correct 40 36 36 36 1 2 47 Prompt 30 30 30 23 23 24 24 22 20

0 Color Shape Pattern Color Shape Pattern Color Shape Pattern Participant 1 Participant 2 Participant 3

120 110

100

Timeout 77 80 75 24 Correction

60 12 Error

Trials 13

37 38 Correct 40 36 36 36 36 1 2 50 41 36 Prompt 23 22 24 24 24 24 20

0 Color Shape Pattern Color Shape Pattern Color Shape Pattern Participant 4 Participant 5 Participant 6

Figure 4. 1 st order trials to mastery. Values for each participant by element are given. Values for correction trials (correction) are omitted, but are equal to errors.

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Participant 4 achieved mastery of colors after 75 trials, 36 of which were correct responses and 13 were incorrect responses; mastery of shapes required 37 trials and included 23 correct responses and 1 incorrect response; mastery of patterns was achieved following 38 trials that included 22 correct responses and 2 incorrect responses.

Participant 5 attained mastery of colors with just 36 trials, including 24 correct responses without error; mastery of shapes was also achieved after 36 trials without error; Mastery of patterns required 77 trials, and that included 41 correct responses and 12 incorrect responses.

Participant 6 attained mastery of colors after 36 trials without an incorrect response; mastery of shapes was also achieved after 36 trials; mastery of patterns required 110 trials which included 50 correct responses and 24 incorrect responses.

The fourth phase (mixed) was conducted following training of all 3 first order elements. The mixed phase results are not reported because it duplicated the presentation of stimuli already mastered in previous phases. Two stimuli from each element were randomly selected and presented to participants as a precursor to second-order trials. However, mastery criterion was applied during the mixed phase, and demonstration of mastery was required by all participants prior to presentation of the second order baseline phase.

Participant’s session times during first order training was not recorded; it was noted that all participants were able to complete training through 7 phases (i.e., first-

33

order and second-order) with total sessions times lasting from one hour and thirty minutes to two hours and thirty minutes.

Second-Order Baseline

The purpose of the second-order baseline phase was to assess each participant’s ability to generalize second-order conditional discrimination behavior from first-order training. During the baseline phase only correct and incorrect responses were of interest. This phase did not include prompted or correction trials.

Timeouts did occur but were not counted as valid baseline trials and are not presented in relevant graphs (see Figures 5 & 6).

Each baseline phase presented 54 trials, 27 integrated and 27 partitioned second-order stimuli pairs (see method section). The 54 baseline trials were comprised of all assigned second-order stimuli, and none were repeated with the

Participant 1 Participant 2 Participant 3 2nd Order Baseline 2nd Order Baseline 2nd Order Baseline 30 30 30 27 27 2 27 4 24 5 24 7 24 5 21 21 21 18 18 18 15 15 15 12 12 25 27 22 23 12 9 9 20 22 9 6 6 6 3 3 3 0 0 Integrated Partitioned Integrated Partitioned 0 Intergrated Partitioned

Correct Incorrect Correct Incorrect Correct Incorrect

Figure 5. Baseline results by condition for participants 1, 2, & 3.

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order of integrated and partitioned trials randomly determined. Participants were given a single opportunity to provide an unprompted response to the correct comparison in each trial.

Results for Participant 1-3 are shown in Figure 5 and results for Participants

4-6 are shown in Figure 6. Participant 1 responded correctly to the integrated condition during 22 trials and recorded 5 incorrect responses. During the partitioned

Participant 4 Participant 5 Participant 6 2nd Order Baseline 2nd Order Baseline 2nd Order Baseline

30 30 30 27 27 27 1 1 1 3 24 24 24 21 21 21 18 18 18 15 15 15 27 27 26 26 12 26 12 12 24 9 9 9 6 6 6 3 3 3 0 0 0 Integrated Partitioned Integrated Partitioned Integrated Partitioned

Correct Incorrect Correct Incorrect Correct Incorrect

Figure 6. Baseline results by condition for participants 4, 5, & 6. condition Participant 1 responded correctly on 23 trials and incorrectly on 4 trials.

Results for participant 2 indicate 20 correct responses and 7 incorrect responses to the integrated condition. Participant 2, under the partitioned condition, correctly responded during 25 trials and incorrectly in 2 trials. It is noted that two timeouts were recorded during integrated trials for Participant 2.

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Participant 3 responded correctly to 27 integrated trials without error. Under the partitioned condition participant 3 responded correctly on 22 trials and incorrectly on 5 trials.

Participant 4 responded correctly in 26 trials and 1 trial incorrectly during the integrated condition. Under the partitioned condition participant 4 responded correctly in 27 trials without error.

Participant 5 recorded 26 correct responses and 1 incorrect response during integrated trials and correctly responded in all 27 trials of the partitioned condition.

Participant 6 responded correctly in 24 trials during the integrated condition and incorrectly in 3 trials. Data for the partitioned condition were 26 correct responses and 1 incorrect response.

Second-Order Discrimination Training

Following the baseline phase, participants were given each second-order element combination (e.g., color/shape) in three separate phases, and trained to mastery. As in first-order training, the total number of trials to achieve mastery (94%) was counted. Each sample and comparison stimuli was presented once with a prompt.

Eighteen prompted trials were presented at the start of each phase, 9 integrated and 9 partitioned comparison trials. The total number of trials to mastery included prompted trials, correct and incorrect responses, and correction trials. Correction trials are only reported in the associated figures. Timeouts are excluded as none occurred during any second-order trial. The minimum number of trials required, that a participant could achieve mastery of either the integrated or partitioned condition, was 27 for each

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condition. All participants, in all phases of training, in both the integrated and partitioned conditions, achieved mastery in the minimum number of trials with two exceptions.

Results for Participant 1and 2 are shown in Figure 7. During the color and pattern (CP) phase Participant 1 responded correctly in 27 trials under the integrated condition, and under the partitioned condition recorded 26 correct responses and 1 incorrect response which was followed by a correction trial. During the color and shape (CS) training Participant 1 responded correctly to 27 trials under the integrated condition and recorded 27 correct responses to the partitioned condition without

Participant 1 Participant 2

28 27 27 2727 27 27 27 27 27 27 27 27 27

18 18 17 18 18 18 18 18 1818 18 18 18 18

9 9

0 0 Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. CP CS PS CP CS PS

Prompt Correct Incorrect Correction Prompt Correct Incorrect Figure 7. Participant 1 and 2 second-order training. Integrated (Int) and partitioned (Part) conditions are shown for second-order phases color/pattern (CP), color/shape (CS), and pattern/shape (PS). errors. Also, when presented pattern and shape (PS) Participant 1 responded correctly to both the integrated and the partitioned conditions with 27 correct responses and no errors.

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Participant 3 Participant 4

28 28 27 27 27 27 27 27 27 2727 27 27 27

18 18 1817 17 18 18 18 18 1818 18 18 18

9 9

0 0 Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. CP CS PS CP CS PS

Prompt Correct Incorrect Correction Prompt Correct Incorrect

Figure 8. Participant 3 and 4 second-order training. Integrated (Int) and partitioned (Part) conditions are shown for second-order phases color/pattern (CP), color/shape (CS), and pattern/shape (PS).

Participant 2 achieved mastery of CP with 27 trials under the integrated and

27 under the partitioned condition, and no errors. Similarly, Participant 2 achieved mastery of CS in both the integrated and partitioned conditions with just 27 trials each, and zero errors. In the PS phase mastery was again achieved without errors, and 27 correct responses to the integrated and 27 correct responses to the partitioned condition.

Figure 8 displays results for Participants 3 and 4. Participant 3 made zero errors during the CP phase, and 27 correct responses under the integrated, and 27 correct responses under the partitioned condition. For the CS phase, Participant 3 had the highest number of errors of any participant. They responded correctly to 26 integrated trials with 1 error, and correctly to 26 partitioned trials with 1 error.

Mastery of PS phase was also achieved with the minimum number of trials, with 27 correct responses in both the integrated and partitioned conditions.

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Responses recorded for Participant 4 indicate zero errors across all three second-order phases. Participant 4 responded correctly in 27 of 27 trials for both the integrated and partitioned conditions during CP, CS, and PS phases, following the prompted trials.

Participant 5 Participant 6

27 27 27 2727 27 27 27 27 2727 27 27 27

18 18 1818 18 18 18 18 18 1818 18 18 18

9 9

0 0 Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. Int. Part. CP CS PS CP CS PS

Prompt Correct Incorrect Prompt Correct Incorrect

Figure 9. Participant 5 and 6 second-order training. Integrated (Int) and partitioned (Part) conditions are shown for second-order phases color/pattern (CP), color/shape (CS), and pattern/shape (PS).

Figure 9 contains the results for Participants 5 and 6. Participant 5 also achieved mastery in the minimum number of trials without error across all phases. In the CP phase 27 correct responses and no errors were recorded for both the integrated and the partitioned conditions. For the CS phase, Participant 5 recorded zero errors and 27 correct responses to the integrated condition and 27 correct responses to the partitioned condition. Lastly, in the PS phase mastery was achieved with 27 correct responses under the integrated condition and 27 correct responses under the partitioned condition.

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Participant 6 also committed zero errors in achieving mastery across all three phases of second-order training. During the CP phase mastery of integrated trials and partitioned trials was in attained with 27 correct responses under each condition and zero errors. In the CS phase mastery was again achieved with 27 correct responses to both conditions and no errors. Lastly, Participant 6 achieved mastery of the PS phase with 27 correct responses under the integrated condition and 27 correct responses under the partitioned condition.

Across all participants during the baseline phase, the results show 4 of the 6 participants performed better during trials where partitioned comparisons were presented than when integrated comparisons were given. For all participants a total of

16 incorrect responses were recorded under the integrated condition with 13 incorrect responses under the partitioned condition.

Across all participants during first-order training (excluding the mixed phase),

4 of the 6 participants required more trials to attain mastery when presented pattern comparisons than with color or shape comparisons. The total number for all participants was 434 trials with pattern comparisons. Interestingly, across all participants the total number of trials required to achieve mastery of colors was 271.

The least number of total trials to mastery was recorded for shape comparisons, with a total of 236 trials.

The second-order training phases demonstrated very little variation between integrated and partitioned conditions across all participants. When second-order element combinations of color and pattern were presented the total number of trials

40

for all participants to attain mastery under the integrated condition was 162 trials, and partitioned trials totaled 163 to mastery.

Similar results were recorded across all participants when color and shape comparisons were presented. Under the integrated condition participants required a total of 163 trials. Similarly, participants required 163 trials to achieve mastery under partitioned condition.

During trials when second-order comparisons were presented that included the elements pattern and shape, no errors were recorded. Under the integrated condition a total of 162 trials were conducted to gain mastery. Likewise, 162 trials were conducted under the partitioned condition to reach mastery.

CHAPTER V

DISCUSSION AND SUMMARY

The present study examined the effect that differences in the physical arrangement of comparison stimuli would have on second-order conditional discrimination performance. Arbitrary first-order relations were trained in preparation for second-order conditional discrimination trials. Results from second-order trials clearly demonstrated the ability of participants to generalize second-order conditional discriminations from first-order training. The results did not provide clear evidence of an effect due to variations in physical arrangement of second-order comparisons, although a difference in response accuracy is seen in some participants. The results suggest that the task may have been too easy; meaning any potential effect from the manipulation of comparisons was undetectable. All participants performed at or near mastery (92%) during the second-order conditional discrimination baseline phase that immediately followed first-order training. Four of the six participants demonstrated mastery in one or both of the second-order comparison conditions (integrated or partitioned). Only two participants failed to demonstrate mastery of either condition during the baseline phase. In subsequent second-order training phases of color-pattern

(CP), color-shape (CS) and pattern-shape (PS), all participants demonstrated mastery of conditional discriminations with a minimum of additional training. Participants demonstrated mastery of both the integrated and partitioned conditions following a single block of prompted trials that initiated each training phase. In fact, across 18

41 42

training phases, that included all 6 participants, only 3 incorrect responses were recorded.

The results of first-order training were similar to research utilizing non-human participants with a symbolic-match-to-sample (SMTS) methodology. In regard to matching performance of pattern comparison stimuli, four participants required more trials to attain mastery during the pattern training phase than either elements of color or shape. Similar results have been demonstrated in SMTS research with pigeons. For example, pigeons learned color (hue) matching more quickly than matching geometric forms or lines. This result was consistent in trials where lines were presented as comparisons whether the sample was a hue or line (Carter & Eckerman,

1975). Additionally, in Redner (2009) pigeons were unable to accurately respond to pattern comparisons, and subsequently only colors and shapes were trained. Patterns presented during the current research may be regarded as more physically complex than the lines Carter and Eckerman (1975) reported. However, the results are consistent if learning histories and exposure to novel line configurations (pigeons) or novel patterns (humans) are taken into account.

The acquisition of first-order SMTS pattern performance may be explained by the composition of the patterns. Each pattern comparison in this study was comprised of multiple dimensions that included repeating lines, curves, shapes and variances of color (black to white). It is unknown which dimension of any given pattern came to exert control over responses, but the multiple dimensions may have created an added difficulty in the learning process. All six pattern comparisons were presented each

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trial, requiring participants to make a simultaneous discrimination between comparisons. Due to their unique nature and complex set of dimensions, it may have been more difficult to learn simultaneous discrimination of patterns than for colors or shapes. Additionally, discrimination of colors is assumed to have been present in the learning histories of participants, as well as many of the shapes (see Table 1, method section).

Along with pattern composition, verbal behavior may have played a role in the learning process. Despite participants’ considerable discrimination skills, those skills did not generalize as readily to learning the mostly unique patterns presented during first-order training. One explanation is the availability of a verbal repertoire already developed by participants for color and shape stimuli. It is unlikely that participants had developed a verbal repertoire in regard to the novel pattern comparisons, with the exception of “checkerboard.” In a post study questionnaire the researcher asked participants to describe any strategies that facilitated the learning process. Several of the participants indicated they applied “meanings” to the stimuli.

While not explicitly stated, the implication is that these participants were using their verbal repertoires to facilitate discrimination and the learning of stimulus relations

(e.g., Pilgram, Jackson, & Galazio, 2000; Saunders & Spradlin, 1990; Potter, Huber,

& Michael, 1997). The relation between samples and pattern comparisons may have been more difficult because a verbal repertoire was not available for the patterns (or samples), unlike color comparisons where we assume all participants had well established color naming responses. Also, common shape comparisons were

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presented such as “star”, “heart”, or “triangle” that were likely part of the participant’s verbal repertoire prior to the study. The additional trials needed for participants to attain mastery of first-order pattern discriminations may reflect the development of a unique verbal repertoire, or more likely, generalization of their current repertoire in a novel manner.

Results from second-order baseline phase, and subsequent training phases, demonstrated fewer variances between phases than between first-order phases. Most importantly, results contrasting the integrated condition with the partitioned condition demonstrated only small differences in correct responding. However, during the baseline phase four of the participants did commit more errors when presented with integrated comparisons than they did with partitioned stimuli. The differences are small, but do suggest an effect due to the configuration of comparison stimuli.

Differential responding to integrated and partitioned stimuli (see Figure 10 for configurations) may be accounted for by similarity to first-order comparisons.

Comparison stimuli presented in second-order partitioned trials were unaltered from comparisons presented in first-order training, unlike the integrated comparisons which were superimposed over each other. If this is in fact the case, then what is the effect of integrating the comparison stimuli? In research that attempted to investigate stimulus processing models, Lockhead (1972) used the term “entangled” when describing the effect of multiple stimulus dimensions. In behavioral terms, entanglement simply means that differential responding is affected when additional stimulus dimensions are present due to changes in stimulus control. In his research,

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Figure 10. Integrated and partitioned comparison configurations.

Lockhead also defined nonintegral stimuli as physical separation along stimulus dimensions (p. 412), which defines partitioned comparisons of the current study. This effect of entanglement was demonstrated by Garner and Felfody (1970) where they showed that sorting speeds for integral stimuli along one dimension were faster when the second dimension did not vary. There was no effect seen with nonintegral stimuli.

The results of Garner and Felfody (1970) and other research (e.g., Johnson,

1970; Lockhead & King, 1977) along with the results of the current research, support the suggestion that stimulus control is affected when first-order comparisons are integrated to become second-order comparisons. Although each dimension is present in its original form in second-order comparisons, the physical relation is significantly altered.

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Sample comparisons (Cherokee language characters) selected for this research were novel to participants. Absence of prior exposure to Cherokee language was a prerequisite for participation. This should have provided control of any confounding variable where learning histories would influence differential responding to samples.

There is some evidence that during second-order trials, in order to discriminate between sample stimuli, participants named (differentially responded to) samples.

For example, Participant 1, in their post-study questionnaire, describes applying their own name to the sample associated with a “flower” shape comparison. The sample

“looked like it had the letter T in it”, which was also the first letter of their name, and their name “means flowers.” Previous research has demonstrated the role that naming plays in differential responding to sample stimuli and the acquisition of conditional discriminations (e.g., Pilgram, Jackson, & Galazio, 2000; Saunders &

Spradlin, 1990).

Overall, the generalization to second-order discrimination performance appears exceptional. That is, performance during second-order discrimination baseline trials was near mastery criteria prior to second-order training. The most likely explanation is the result of a ceiling effect. As stated, the current study was an extension of second-order conditional discrimination research with pigeons. As such, the number and complexity of sample and comparison stimuli were similar to the prior research (Duroy, 2005; Redner, 2009). Considering the advanced nature of human discrimination behavior, it appears that the task was simply too easy. Another indication of a ceiling effect was seen in the number of sessions required for

47

participants to attain mastery. It was anticipated that 4 to 6 sessions would be required to complete all phases. Unexpectedly, most participants were able to complete all phases in a single session, and no participant required more than two.

However, the results of the second-order baseline phase indicate that the ceiling affect was not absolute. Participants did not respond with 100% accuracy, and improvement was seen during second-order training phases. This suggests that the methodology used in the current research may be a viable starting point for considering future studies of second-order conditional discrimination in humans where physical properties of comparisons are considered.

There remains a large gap in our understanding of conditional discrimination learning in humans. If future research investigating basal factors affecting conditional discrimination learning is to be conducted, then the importance of such research needs to be emphasized. Much time has been spent examining procedural factors that affect discrimination learning in humans (e.g., Jordan, Pilgrim, & Galizio, 2001;

Pilgrim et al., 2000; Saunders & Spradlin, 1990; Williams, Johnston, & Saunders,

2006). Additionally, related research in the areas of contextual control, categorization, and concept formation is plentiful (Zentall, 2002). However, research which directly addresses the most fundamental aspects of conditional discriminations is still needed.

A visit to any classroom will reveal a wide variety of complex stimulus arrangements.

Typically, elementary classrooms have pictures of the alphabet on a wall, maps, posters, and charts are common, along with many other stimuli. The question remains, “How does the arrangement of these stimuli affect conditional

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discrimination learning?” The implications of such research could conceivably affect the way we organize classrooms, textbooks, road signs, or aircraft cockpits. A prime example of this research’s relevance may be found in the ubiquitous cellular phone.

Corporations spend vast amounts of resources on user experience design and user interfaces. How those interfaces are designed may be improved significantly with additional research along the lines of the current research.

Limitations

The principle limitation of this study is related to the ease with which participants achieved mastery. Six variations of each element, provided 18 first-order stimuli pairs, this is a relatively small number in light of the vast number available to participants in daily life. However, the potential impact of a small selection of stimuli is unknown. The utilization of additional stimuli may present an opportunity for future research.

In conjunction with the small number stimuli, the use of stimuli based on familiar colors and shapes had the potential to facilitate second-order mastery performance. In previous research (e.g., Perez-Gonzales & Martinez, 2007; Perez-

Gonzales & Serna, 2003) on contextual control novel stimulus shapes were used exclusively. It may be beneficial to present novel stimuli, but it is also recognized that novel stimuli may not accurately represent the most common physical properties that are encountered in discrimination learning.

Additionally, the participants selected for this study had extensive learning histories. It has been demonstrated that learning histories can affect current

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discrimination learning (e.g., Harlow, 1950). The principle limitation of selecting college students for this study is the inability to generalize findings to the general population. This is particularly true in the case of children that are still in the process of acquiring conditional discrimination behavior and lack long learning histories.

It is likely that the study would have benefited from a larger selection of stimuli. The decision to select 18 first-order stimuli pairs, which allowed for 54 second-order pairs, was modeled on the research of Duroy (2005) and Redner (2009).

In order to extend their pigeon research to humans, it was logical to make only incremental changes to the SMTS design. Pigeons demonstrate difficulty acquiring second-order conditional discrimination behavior, and humans acquire it easily.

Understanding that divide requires examination of the most basic factors common to both humans and pigeons. Presentation of stimuli based on color, shape, and pattern from the prior research were also chosen with this idea in mind. Results indicate further consideration is required with regard to the number of stimuli, the dimensions, and potentially the manner of presentation. Like the earlier research, laptop computers were also used to display the stimuli and manage trials. How this generalizes to more natural stimuli encountered during discrimination learning is yet unknown. However, the use of computer screens does provide a readily available and cost effective method of manipulating fundamental physical properties as was done in the current research.

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Future Research

There are a number of ways in which future researchers might address limitations of the current research. There are many studies that have utilized younger participants (e.g., Jordan, Pilgram, & Galizio, 2001; Perez-Gonzales & Serna, 2003).

Future research of basal factors in the acquisition of conditional discrimination behavior might benefit greatly from the use of younger participants. Dependent upon age, these individuals are still in the process of acquiring sophisticated discrimination and verbal skills, making it more likely that basal factors can be identified and studied. This may make it possible to retain basic stimulus dimensions used in the current research without concern for the effect learning history may have on results.

An interesting aspect of the current research is the role that language plays on the acquisition of conditional discrimination behavior. It was not a primary point of investigation, but post study questionnaires provided to participants, offers an interesting problem for human researchers. If physical properties of stimuli are to be examined, how can researchers manage verbal behavior as a variable? Studies involving younger participants may provide one avenue.

One problem for future research is how to make the second-order conditional discrimination task more appropriate to human second-order conditional discrimination skills without introducing additional variables. The ceiling effect encountered in the current research needs to be addressed. The introduction of additional stimuli sets, based on the same basic dimensions, may provide the simplest solution. Increasing the number of stimuli would increase the task difficulty without a

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major revision of methods. In addition, a larger set of alternative comparisons would be available for presentation in any given trial. For instance, during second-order trials random selection of alternate comparisons did not guarantee a second-order response was necessary to select the correct comparison. In approximately 50% of trials participants could select the correct second-order comparison based on a single dimension. For example, in any trial where the correct comparison contained red, the total number of comparisons that contained red could potentially vary from one to six across trials. This was not considered critical because mastery criteria were well above the single dimension selection potential. However, a larger set of alternative comparisons along with software adjustments could eliminate the effect completely.

Lastly, in preparing the current research, consideration was given to creating third-order comparisons from the three elements available. Creation and implementation of third-order comparisons would be a direct extension of the current research and require few changes to methodology. A third-order discrimination task should provide increased difficulty while retaining the current stimuli, and offer opportunity to compare current results to third-order conditional discrimination performance.

Summary

The current research successfully extends the second-order conditional discrimination research with pigeons (Duroy, 2005 & Redner, 2009), utilizing a

SMTS methodology, to humans. The results may only be suggestive of differential responding to the integrated and partitioned second-order conditions, but they are

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encouraging. The results from first-order phases and the second-order baseline phase clearly indicate that there is an area of investigation worth pursuing. One goal of the current study was to clarify terminology for more primary research with the introduction of the terms integrated and partitioned. Hopefully future research will utilize a more precise terminology to describe physical arrangements of stimulus dimensions.

The importance of understanding basal factors affecting acquisition of conditional discrimination learning should not be ignored, but this line of inquiry remains largely unexplored. Without a clear understanding of factors affecting the discrimination process, explanations of human learning remain incomplete.

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