EXPERIMENT 1 Distinctive control of decision time: Method Subjects. Forty right-handed undergraduate students from the Same-different judgments of University of Waterloo served as Ss. Their participation partially fulfilled a simultaneously heard course requirement in introductory psychology. Stimuli. The phonemes RONALD A. COLE and BRIAN SCOTT Ib, m, v, g, d, n, Z, sl and the University of Waterloo, Waterloo, Ontario, Canada phonemes Ii, I, e, ae, u, U, 0, al were used as stimuli. All consonant Ss decided whether dichotically presented consonant or vowel phonemes were phonemes were paired with the vowel "same" or "different" in a reaction time (RT) task. Results indicated that t e }, The distinctive·feature "different" responses were made on the basis of a serial, self-terminating scan of composition of these phonemes, distinctive feature differences between phonemes. "Same" responses were according to Halle's (1962, 1964) considered too fast to be accounted for by this process and were discussed as a distinctive-feature system, is shown in separate parallel process. Recognition of dichotically presented appears Table 1. It can be seen that each vowel to involve a third process in which phonemes are also identified in terms of their is uniquely described by a + distinctive features. or - value on five acoustic dimensions, while each consonant phoneme is It is a general rule that the more similarity of the two syllables. uniquely described by a binary value different two stimuli are, the faster There is some evidence to support on six dimensions. one may decide that they are different this notion. Chananie and Tikofsky It can be seen in Table 1 that pho­ (Egeth, 1966; Bamber, 1969). (1968) found no difference in the RT to nemes vary greatly in terms oftheir dis­ Experiments that have tested this successively heard single- words tinctive features. For example, IiI and notion by examining reaction time which differed in their initial [e] differ by only one distinctive fea­ (RT) to successively heard phonemes by one, two, three, or four ture, while taal and lUI differ by five differing by few or many distinctive distinctive features. This result distinctive features. Similarly [tn] and features have yielded ambiguous suggests that phonemes were recorded Ibl differ by a single distinctive results. For example, McInish and into word representatives in auditory feature, while Iml and 1st differ by six Tikofsky (1969) presented Ss with memory and these word distinctive features. successive pairs of spoken consonants representatives could be compared To insure accurate reproduction of (paired with la/) that either were the without reference to individual a particular stimulus on a given trial, same or differed by one or two phonemes or their distinctive features. the 16 consonant and vowel phonemes distinctive features, according to the One way to decrease the possibility were recorded in a male voice and Miller-Nicely (1955) distinctive feature that Ss use the time between stored on disk tape in an IBM 360/44 system. Ss were required to decide, as successive presentations of a stimulus computer. Each sound was cut to a quickly as possible, whether the to recode a phoneme from a set of length of exactly 250 msec to insure second consonant was the same as the distinctive features to a name code is simultaneity of onset and offset. The first. It was found that RT was fastest to present two phonemes stimuli were recorded onto magnetic for "same" responses, and faster for simultaneously during a recognition tape by attaching a Sony Model pairs of consonants that differed by task. The present experiment was TC540 stereo tape recorder to the two, rather than one, distinctive designed to test this hypothesis for computer output and programming features. dichotically presented pairs of the computer to play the required In a similar procedure, Cole consonants and . It was phonemes simultaneously into (unpublished data) presented Ss with predicted that the more different two separate channels of the tape recorder. pairs of spoken consonants (C, D, P, consonants or vowels are in terms of The computer also recorded a T) or vowels (E, A, 0, "00") their distinctive·feature composition, 250-msec warning tone on Channel A separated by .5, 2, or 8 sec in a the faster S will decide that they are 2 sec prior to the onset of the stimuli. same-different RT task. While "same" different. The onset of the stimulus recorded on responses were faster than "different" responses, no differences were found in RT to consonants or vowels differing by one, two, or three Table 1 distinctive features. Distinctive Feature Composition of Consonant and Vowel It is possible that Ss in Cole's Phonemes Used In This Experiment experiment originally identified each spoken letter in terms of its distinctive Ibl lm] lv] Igl Idl Inl [z] lsI features, but recoded each syllable Grave + + + + into a higher-order response. This Diffuse + + + + + + could be accomplished, for example, if Strident + + + S generated the letter name Nasal + + corresponding to each syllable (e.g., + + + "p" for Ipi/) prior to the presentation Voiced + + + + + + + of the second syllable. In this case, when S was presented with the second IiI III [e] leI luI lUI 101 lal syllable, he would convert this Flat + + + stimulus to a letter in order to make a Compact + + same-different judgment. Therefore, Diffuse + + + + one would not expect RT to vary as a Grave + + + + function of the distinctive-feature Tense + + + + +

Perception & Psychophysics, 1972, Vol. 12 (1B) Copyright 1972, Psychonomic Society, Austin, Texas 91 Warning Stimulus A EXPERIMENT 2 Tone The localization data revealed that S AJI._---=-~_...:...-2 sec 7 sec could be responding 'different" to Channel pairs of consonants based on their 250 msec 250 msec subjective localization, rather than comparing the sounds in terms of their distinctive features (of course, it is possible that localization could be based on a distinctive-feature comparison). In order to eliminate S's Stimulus B ability to localize the consonant sounds, an experimental tape was Channel B ...... r1... _ prepared in which the two stimuli on each trial were always presented in 250 msec different voices. Thus, one sound on each trial was spoken in a male voice, while the other was spoken in a female Fig. 1. Placement of stimuli on a single dichotic trial. voice. This manipulation does not affect the relative distinctive-feature Channel B activated a Hunter Analysis of variance revealed that RT similarities of the sounds. However, 100-msec timer, which was stopped by varied as a function of the the localization data from 10 Ss S's "same-different" response to the distinctive-feature similarity of the presented with 58 mixed-voice pairs two stimuli. A 7-sec pause separated stimulus pair (F = 7.07, df = 5/190, revealed that S always heard the two successive trials. A typical stimulus p < .001). Again, there was no sounds at each ear, even when the sequence is illustrated in Fig. l. interaction between phoneme type same syllable was presented to both Procedure. Ss were assigned and phonemic distinctive-feature ears. Since presenting the stimuli in randomly to either the consonant similarity. two voices eliminates localization group or the vowel group. Each S was One possible explanation of these effects due to the distinctive-feature presented with 224 trials consisting of data is that S was responding "same" similarity of the consonant phonemes, each sound paired with itself 14 times or "different" to each pair of sounds Ss were presented with these stimuli for a total of 112 "same" trials and based on their apparent localization in for same-different judgments in aRT paired with each of the other seven his head. For example, "same" experiment. sounds twice (once to each ear) for a responses might be based on hearing total of 112 "different" trials. "Same" the two sounds fuse into a single Subjects and "different" trials were presented sound near the center of the head, Twenty right-handed undergraduate in random order. while "different" responses would be students from the University of Each S was seated at a small table, based on hearing the sounds as further Waterloo served as Ss. All Ss were holding a two-way toggle switch apart. Since distinctive features students in an introductory grasped between his thumb and provide a general description of the psychology course, although forefinger. S was instructed to move physical similarity of any two sounds, participation was voluntary. the switch to the right as quickly as pairs differing by many distinctive possible when the stimuli in both ears features could be localized furthest were the same and to the left when the apart in the head. stimuli were different. Stimuli were If this reasoning is correct, one presented to S via a Sony Model would expect to find an orderly TC540 stereo tape recorder and Koss relationship between the Pr04A stereo headphones, so that distinctive-feature similarity of two stimuli were heard simultaneously in sounds and their subjective both ears. After each trial, E recorded localization in the head. To test this S's RT. The experiment commenced hypothesis, 20 naive Ss were randomly • following 10 practice trials. presented with 58 pairs of either consonants or vowels, and asked to localize the two sounds. S localized Results the sound by placing the appropriate .. Analysis of variance revealed that mark(s) on a semicircle representing •;:: RT for "same" responses was not the top 90 deg of a circle with a radius significantly faster than RT for of 32 mm. "different" responses. However, the Table 2 displays the mean o faster RT for consonants than for separation in millimeters for pairs of vowels (595 vs 716 msec) was consonants and vowels differing by 0 c . significant at the .05 level (F = 4.12, to 6 distinctive features. For both df = 1/38). There was no interaction consonants and vowels, there was a between phoneme type (consonant vs marked tendency for Ss to respond to vowel) and response type ("same" vs identical stimuli at each ear by placing 012345. "different"). .--1 a single mark at the center (top) of the MUM". Of 'IATU.IS O.,...IMT Figure 2 describes the RT to pairs semicircle. For consonants, there was a of vowel phonemes differing by 0 to 5 direct relationship between degree of Fig. 2. Mean RT to dichotically distinctive features and pairs of separation and distinctive-feature presented consonants differing by 0 to consonants differing by 0 to 6 similarity: the more different two 6 distinctive features and to vowels distinctive features. For both sounds in terms of their distinctive differing by 0 to 5 distinctive features. consonants and vowels, there was an features, the further apart they were Data were summed over 20 8s in each orderly decrease in RT to phonemes localized. No such tendency was condition. sharing fewer distinctive features. observed for vowels.

92 Perception & Psychophysics, 1972, Vol. 12 (IB) Stimuli However, the data from this and other The consonant phonemes displayed experiments (e.g., Egeth, 1966, in Table 1 were used as stimuli. Each Bamber, 1969) reveal that "same" consonant paired with lal was responses are at least as fast as the 1100 recorded in a male voice and a female fastest "different" responses. To voice, and stored on disk tape in an account for this discrepancy in the fast IBM 360/44 computer. A stimulus RT for 'same" responses, Bamber tape was then made, using the same (1969) hypothesized an independent 10 pairs of stimuli presented in process, called the "identity reporter," Experiment 1. However, on each trial, which responds only to identical a ·;: the syllable presented to one ear was stimuli. Egeth and Blecker (1971) 1000 heard in a male voice, while the recently found that RT for "same" Z syllable presented to the other ear was and "different" responses may be 2.. heard in a female voice. For each differentially influenced by the ~ • 950 possible pairing of the stimuli, the familiarity of the stimuli, a result • 0 male and female voices were heard which supports the independence of equally often in the left and right ears. the two processes. Several experiments have suggested Procedure that a "same" response may be based The experimental procedure was on a direct "physical" match of two identical in Experiments 1 and 2. stimuli. Evidence for a physical or sensory comparison has been o 2 3 4 S 6 Results demonstrated by Posner (1969) for (sam.) Figure 3 displays RT to pairs of visual stimuli and by Coltheart and NUMBER OF FE4TURES DIFFERENT consonants differing by 0 to 6 Allard (1970) for auditory stimuli. distinctive features. It is notable that While a physical match may occur in RTs to all pairs were significantly some experiments, it is clear that this Fig. 3. Mean RT to dichotically longer in Experiment 2 than in process will not account for the fast presented consonants differing by 0 to Experiment 1. Analysis of variance RT of "same" responses for syllables 6 distinctive features. The two revealed no differences in RT to heard in different voices. In this case, consonants presented on each trial "same" or "different" pairs. However, S must respond "same" without were spoken in a different voice. there were significant differences in making a physical match. RT to pairs differing by 1 to 6 The results of experiments which different processing levels. It is likely distinctive features (F = 7.68, df = require recognition of dichotically that Ss decide that two phonemes are 5/95, P < .01). A trend analysis presented phonemes rather than "different" on the basis of their revealed a significant linear component same-different judgments suggest that distinctive features before naming the (p < .02) to the decreasing function decisions concerning the names of two individual phonemes presented to each displayed in Fig. 3. phonemes may involve a third level of ear. processing. This contention is It appears that recognition of DISCUSSION supported by an examination of the simultaneously heard phonemes also The present experiment number and types of errors made in requires identification of their demonstrates that same-different the two types of experiments. In the distinctive features. Halwes (1969) judgments about simultaneously heard present experiment, there were very required Ss to identify pairs of phonemes are based on a comparison few errors (less than 2%), and these dichotically presented CVC syllables of their distinctive features. The direct were mostly anticipatory errors in that differed by a single phoneme. In a relationship between RT and which S knew immediately whether or very sophisticated analysis, Halwes distinctive-feature similarity for not he had made an error. On the discovered that recognition errors syllables differing by a single phoneme other hand, experiments requiring Ss resulted from the "blending" of the suggests a serial self-terminating to name the phonemes presented to distinctive features presented to each model, as discussed by Bamber (1969). each ear yield a large number of errors. ear. For example, Ibl (front, voiced) According to this model, two stimuli For example, Ss in a dichotic listening and ItI (middle, unvoiced) combine to are serially scanned along a number of experiment performed by Shankweiler produce Ipl (front, unvoiced), which is dimensions until a differentiating and Studdert-Kennedy (1967) a recombination of the individual feature is found which terminates averaged only 40% accuracy in features in Ibl and lt], These and other processing and elicits a 'different" identifying the consonant or vowel studies (e.g., Miller & Nicely, 1955) response. The more dimensions by presented to each ear. Thus, Ss are suggest that phonemes are recognized which two stimuli differ, the faster a able to decide with great accuracy as sets of independently processed discriminating feature will be located, whether two simultaneously heard distinctive features. resulting in a faster RT. phonemes are the same or different, In summary, it has been argued that If comparisons were based only on a but have great difficulty in naming the two processes are involved in serial self-terminating model, then individual phonemes. These results same-different judgments of "same" responses would take longer suggest that a same-different response simultaneously heard phonemes, and than the slowest "different" responses. and an identification response engage that a third process is involved in n ami ng simultaneously heard phonemes. The present experiment suggests that "same" responses occur Table 2 too fast to be accounted for by a serial Mean Distance in Millimeters for Sounds Subjectively Localized in the Head self-terminating scan, suggesting that o 1 2 3 4 5 6 "same" and "different" responses involve independent processes. Vowels .9 23 25 23 26 25 Deciding whether two phonemes are 34 Consonants 1 26 28 29 30 33 different seems to require that S

Perception & Psychophysics, 1972, Vol. 12 (1B) 93 compare phonemes in terms of their Psychophysics, 1969, 6, 169-174. HALWES, T. G. Effects of dichotic CHANANIE. J. D., & TIKOFSKY, R. S. on the perception of speech. Supplement distinctive features. This comparison Reaction time and distinctive features in to: Status Report on Speech Research. can be accomplished without regard to speech discrimination. Paper presented at Haskins Laboratories, September 1969. the ear in which the phoneme was the meeting of the American McINISH: J. R., & TIKOFSKY. R. S. heard. As long as S is not required to Psychological Association, San Francisco, Distinctive features and response latency: 1968. A pilot study. Perception & recognize the phonemes, he has only COLTHEART, M., & ALLARD, F. Psychophysics. 1969.6, 267·268. to decide whether the feature values Variations on a theme by Posner: MILLER. G.• & NICELY, P. An analysis of on any of several independently Physical and name codes of heard letters. perceptual confusions among some Paper presented at the 10th annual English consonants. Journal of the processed dimensions are different. In meeting of the Psvehonomic Society, San Acoustical Society of America, 1955.27. order to recognize the phonemes Antonio, November 1970. 338-352. presented to each ear, S must retain EGETH, H. E. Parallel versus serial processes POSNER.. M. Abstraction and the process of laterality information for each of these in multidimensional stimulus recognition. In J. T. Spence and G. Bower discrimination. Perception & (Eds.), The psychology of learning and features. The identification of the Psychophysics, 1966, I, 245-252. motivation. Vol. 3. New York: Academic complete set of features presented to EGETH, H., & BLECKER. D. Differential Press. 1969. each ear thus requires a more complex effects of familiarity on judgment of SHANKWEILER. D .• & analysis than that involved in a sameness and difference. Perception & STUDDERT-KENNEDY, M. An analysis Psychophysics, 1971.9.321-326. of perceptual confusions in identification same-different judgment. HALLE. M. in generative of dichotically presented CVC syllables. grammar. Word. 1962. 18. 54·72. Quarterly Journal of Experimental REFERENCES HALLE. M. On the bases of phonology. In Psychology. 1967, XIX, 59'63. BAMBER, D. Reaction times and error rates J. A. Fodor and J. J. Katz (Eds.). The for "same"-"different" judgments of structure of . Englewood Cliffs, multid'mensional stimuli. Perception & N.J: Prentice-Hall, 1964. (Accepted for publication April 10. 1972.)

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