and the Mind

A (Limited) Call for a Return to

DAVID A. LIEBERMAN University of Stirling, Scotland

ABSTRACT: Though perhaps few psychologists would information of truly impressive accuracy and re- now describe themselves as strict behaviorists, a re- liability. Assuming for the moment that this is view of the literature suggests that methodological and so—and I shall return to the validity of this as- radical behaviorism continue to exert a powerful influ- sumption later—why have some psychologists been ence on current research, even in such nominally cog- so reluctant to use introspection as a scientific nitive areas as imagery and hypothesis learning. In technique? The answer, I believe, is that although many ways this influence has been healthy, leading to a productive emphasis on the importance of environ- experimental psychologists have largely abandoned mental variables in behavior, but some of its the language of behaviorism, many have continued consequences have been rather less benign. After re- to be influenced by its philosophical and methodo- viewing the historical arguments against the use of logical assumptions. The mind, in this view, is introspection, this article concludes that most either are at best of uncertain epistemological status, and invalid or no longer possess their original force, so the introspection is, in any case, an inherently flawed benefits from a wider use of introspection now seem tool for its analysis (see, e.g., Kanfer, 1968). likely to outweigh the possible costs. This view is not quite so baseless or absurd as some critics have implied (e.g., Joynson, 1974), Over the last two decades there has been a dra- but neither does it represent a fully balanced as- matic increase in cognitively based analyses of be- sessment. The dangers of introspection (and of havior, with terms such as memory, attention, and the mind), I argue below, are not nearly so great expectation becoming part of the common parlance as has sometimes been suggested. Before trying of our profession. If psychologists have largely i to develop this point in any detail, however, it may accepted the language of mentalism, however, there be useful to review briefly the history of introspec- has in many cases been a continuing reluctance to tion in order to provide some perspective on the accept the reality of the processes to which these issues involved. terms refer, and thus a reluctance to study these processes through the use of introspection. In some cases this caution is undoubtedly healthy. The Emergence oj Introspection The mere fact that people say they experienced The early experimental psychologists—Wundt, some thought or emotion, after all, by no means Titchener, Kulpe, for example—took as their goal proves that they did so. Suppose, for example, that an understanding of the human mind, and to this the defendant in a murder trial was a young and end they relied on the technique of introspection, attractive woman. Even if all the jurors involved the observation by a subject of his or her thoughts insisted that they had not been influenced in any and feelings. As used in the early psychological way by her appearance, we might still question laboratories, however, introspection bore little re- whether it had played some rale, and experimental semblance to the more casual processes of self- evidence from related situations suggests that awareness familiar from everyday life. Introspec- our skepticism might well be justified (see, e.g., Nisbett& Wilson, 1977). If introspective reports are sometimes wrong or Requests for reprints should be sent to David A. Lieber- misleading, however, there is equally compelling man, Department of , University of Stirling, evidence that in some instances they may provide Stirling, Scotland FK9 4LA.

Vol. 34, No. 4, 319-333 AMERICAN PSYCHOLOGIST • APRIL 1979 • 319 Copyright 1979 by the American Psychological Association, Inc. 0003-066X/79/3404-0319$00.7 5 tion was regarded as a skill, requiring just as much As this inability to agree became increasingly com- training and practice for its development as, say, mon, introspection began to appear increasingly learning to be a professional wine taster. In sterile and unsuitable as a vehicle for scientific Wundt's laboratory, for example, subjects were re- progress. quired to practice at least 10,000 separate intro- Reacting to the growing sense of stagnation and spections before they were considered ready to futility, Watson and other early behaviorists vig- participate in a genuine experiment, and once orously criticized introspectionists for their pre- properly trained a subject might require as much occupation with mental functioning and called in- as 20 minutes to report fully on his or her ex- stead for a new emphasis on overt behavior. The periences during a l.S-sec experiment (Boring, goal of psychology, they argued, should be the 19S3). In some areas—notably psychophysics— practical one of understanding (and thus poten- this painstaking effort paid off handsomely, and we tially changing) human behavior, and the proper still owe much of our current knowledge to this method for achieving this goal should be the ob- early experimentation. Within only a few decades, jective observation of behavior. It is perhaps not however, the systematic use of introspection as a always appreciated, however, that two logically scientific method was to disappear almost com- separable arguments are implicit in this position: pletely. One might well agree that the proper goal of psy- One reason for its demise was the impact of chology should ultimately be the prediction and Freud's revolutionary theories of the unconscious. control of behavior yet still argue that one method The foundation of introspective analysis was the for achieving this goal could be the systematic belief that all of the mind's functioning was acces- study of mental processes. Indeed, this forms the sible to conscious observation, for unless every thesis of this article: Behaviorism succeeded bril- aspect of human thought and emotion could be liantly insofar as it argued for a new emphasis on observed, introspection could provide at best only behavior, both as goal and as method, but in re- an incomplete and fragmented picture of mental acting to the limitations of introspection it went functioning. If consciousness represented only too far in rejecting it totally. Introspection is the visible tip of the iceberg, with vast areas of limited in what it can achieve, but an acknowledg- the mind permanently curtained off behind pow- ment of its limitations does not thereby require erful defensive barriers, then introspection was its total proscription. This rigid rejection may clearly doomed. The same conclusion was sug- initially have been the only way in which a new gested, moreover, by the introspectionists' own generation of psychologists could be shielded from findings. In trying to analyze the thought pro- the siren call of mentalism, but in their efforts to cesses involved in solving a problem, for example, avoid the difficulties posed by introspection, the subjects reported experiencing a sequence of early behaviorists may also have ignored the ad- thoughts, each one moving closer to the goal of vantages to be gained. As psychology has grown solution, but they could discover no conscious more mature, however—thanks in no small part process that guided these thoughts and determined to the work of behaviorists such as Watson and which one occurred at which time, Ach (1905) Skinner—we may have now reached a point where coined the term determining tendency to describe we are sophisticated enough to reap the fruits of the unconscious process, hidden from introspection, introspection without becoming entangled in its that guides thinking along its proper course. thorns. Inaccessibility of mental processes was bad To develop this case, I first consider some of enough, but the problem was compounded by the the arguments that have been raised against the inability of introspectionists to agree even when use of introspection as a scientific technique, and the object of study was ostensibly accessible. In I argue that, ultimately, the only reasonable cri- the controversy over imageless thought, for ex- terion is an empirical one: whether or not intro- ample, workers in Kulpe's laboratory reported that spective data help us to understand behavior. abstract thoughts could occur without being ac- I then turn to an examination of such data and companied by any form of mental imagery. Titch- argue that at least in some areas introspection has ener, on the other hand, insisted that when he already contributed significantly to our under- introspected he could see "vague, evanescent pat- standing of behavior and thus to our ability to terns of sensations and images" (Boring, 19S3). modify it. Finally, having argued for the ad-

320 • APRIL 1979 • AMERICAN PSYCHOLOGIST vantages of introspection as an empirical method, for producing images, say, without also producing I consider some of the implications of its use for neural activity, and there is thus no way of de- the status of the mind itself within psychology. termining whether the images by themselves could influence behavior. Even if the mind were only an epiphenomenon, moreover, this would not be an Does the Mind Exist? argument against studying it. Consider, for ex- ample, the status of fever. Fever is in some There are several possible strategies within the sense an epiphenomenon produced by disease: general framework of behaviorism for dealing with When the body is invaded by bacteria, blood is the problem of mental events. Perhaps the sim- diverted from the periphery of the body to the plest, most commonly associated with John B. center so that the white corpuscles carried by the Watson, is simply to deny their existence. Wat- blood can be concentrated in the body's core, where son himself, however, vacillated in his position they can then attack the invading bacteria. One on this issue. On some occasions he did indeed result of this diversion of blood from the periphery appear to deny the existence of the mind (e.g., is that less heat is carried to the skin, where it is Watson & McDougall, 1929), but on others he normally dissipated, and the body temperature argued simply that it could not be usefully studied thus begins to rise. Fever, then, is not directly by psychologists: "If you will grant the behavior- produced by the bacteria that invade the body ist the right to use consciousness in the same way but is a by-product of the body's reaction to that as any other natural scientist—that is, without invasion. If fever were eliminated by giving a making consciousness a special object of observa- patient aspirin, for example, this would relieve tion—you have granted all that my thesis re- the symptom but would have no effect on the quires" (Watson, 1913, p. 174). In any case, underlying pathogenic process. whatever Watson's personal beliefs may have been, In some sense, then, fever is an epiphenomenon: virtually no psychologist in the years since has an incidental by-product of disease rather than chosen to attack the mind by denying its exis- part of its causal mechanism. Does this then tence. Whatever the merits of such a position may imply that fever is irrelevant to disease and should be, therefore, I shall henceforth ignore it and not be studied? The answer, quite obviously, is assume that there is at least a tacit consensus that no. Provided that body temperature is correlated the mind—however we may choose to define it— with the causal processes, its measurement can does exist. The real issue, therefore, is not provide the physician with valuable information whether the mind exists but whether it is a proper for both treatment and prevention. Whether fever, object for scientific investigation.1 or the mind, is an epiphenomenon, therefore, is irrelevant to its scientific investigation. The only Is the Mind an Epiphenomenon? question is whether such measurement will help the scientist in reaching his or her goal—in the A second, somewhat more subtle argument has case of the psychologist, the prediction and con- been to accept that the mind exists but to deny trol of behavior. Provided that mental and that it plays any causal role in behavior. Ac- neural states are at least correlated, therefore— cording to the epiphenomenal version of this posi- and epiphenomenalists would in no way deny this tion, events in the external world trigger a chain —the possibility that the mind is not causal is not of neural activity, and this neural activity eventu- an adequate argument against studying it. ally results in overt responding. As a result of this activity in the brain's neurons, the state we call consciousness may arise, but this state is only 1 Perhaps it is worth noting at this point that an ac- an incidental by-product of the neurons' electrical ceptance of the mind's existence does not necessarily imply any commitment to a dualistic framework. Thus, although activity and does not itself play any causal role some philosophers have argued that mind and body exist in directing behavior. in totally different realms, with neither influencing the other, others have argued with equal force that the mind One objection to this view might be that it is is the brain, or rather, the neural processes of the brain. impossible to test empirically, since as far as we The assumption that people really do have thoughts and feelings, therefore, does not necessarily imply that these now know, neural and mental states seem to be phenomenological experiences exist in some nonphysical perfectly correlated. There is no known technique universe, and no such implication is intended in this article.

AMERICAN PSYCHOLOGIST • APRIL 1979 • 321 Methodological Behaviorism might allow considerable confidence in the original report's accuracy. Still a third argument against the use of intro- Similarly in psychology, even if no external ob- spection is that by its very definition it involves server can directly observe a mental event, we the observation of private events, ones not acces- may still evaluate reports of such events in terms sible to outside observers. If observations cannot of their correlation with other data. In an experi- be independently confirmed, however, there is no ment by Cohen (Note 1), for example, subjects way to determine whether they are true or false, who were exposed to an absolutely uniform visual accurate or inaccurate. According to this position, field (Ganzjeld) for extended periods of time some- therefore, any psychology that relied on introspec- times reported they could no longer see—not that tion would inevitably be doomed to failure. With- there was nothing to see but that they had liter- out any means of confirming observations, dis- ally lost the sense of seeing at all. At first, it agreements will inevitably arise and progress will might seem unlikely that vision itself would really become impossible. disappear in this way, and it is in any case difficult There is some validity to this objection: When to see how such a claim could be tested. It was a person reports having a headache, for example, found, however, that reports of "not seeing" were it is obviously very difficult for any external ob- reliably correlated with systematic changes in server to confirm this directly. Reports from other brain-wave activity and also with the disappear- observers, however, are by no means the only way ance of saccadic eye movements (see also Tepas, of evaluating the validity of a report. One Note 2). And what is even more striking, when measure of a report's accuracy, for example, is its various test stimuli, such as a circle or a star, were reliability—can the observation be repeated with introduced during these periods, subjects were un- the same results?—and this technique has been able to detect their presence. used extensively, and successfully, in psychophysi- It is possible, of course, that Cohen's subjects cal studies. If a subject reports that one light were lying: Perhaps to maintain their credibility appears to be twice as bright as another, for ex- they were deliberately denying seeing the test stim- ample, we may present these two lights again later uli, even though they really could detect them. on in the test series, observe whether this response This explanation, however, could also be tested. is still the same, and so on. Furthermore, we may Thus, as a test stimulus we might use a light that test more than one subject, and if each subject had been previously paired with a severe electric independently reports the same observation—LI shock, and monitor the subject's galvanic skin re- = 2La—then we may begin to have considerable sponse (GSR) during test presentations. If test confidence in the reliability of the report. It was presentations during periods of "not seeing" pro- precisely this method, after all, that allowed duced no GSR, this would be a fairly strong in- Wundt and Fechner to establish the laws that now dication that the stimulus had genuinely not been bear their names and that still form the corner- detected. stone of modern psychophysics. The problem of confirming subjective reports, Even in cases where repetition is not possible, then, is by no means insoluble. A person who we may still evaluate the accuracy of a report in reports feeling hungry is really no different from terms of its correlation with other evidence. Sup- one who reports seeing a meteor. Each of these pose, for example, that an astronomer on vacation assertions is simply a verbal report of subjective in a lonely forest later reports having seen a experience, and the fact that the stimulus for one gigantic meteor pass overhead. Ideally, other as- originated outside the body (in reflected light) tronomers might like reports from other observers rather than inside it (say, in stomach contractions) to confirm this sighting, but the absence of such does not give the former report any greater valid- ity. Reports involving only a single observer may evidence would hardly mean that the original re- well be more difficult to confirm—physicists might port would have to be ignored. In the case of the well prefer 100 observers to one, and so might we meteor, for example, investigators might trace —but the fact that only one observer is present radar records at nearby airports for any sign of does not in itself suggest that the evidence should disturbance, or look for impact craters in the not be used. The real question is the empirical nearby woods, and so on. No piece of evidence one of whether the report is useful in predicting by itself might be sufficient, but together they and controlling behavior. If it is, then what

322 • APRIL 1979 • AMERICAN PSYCHOLOGIST earthly purpose is served by arbitrarily choosing of the causal sequence. Furthermore, Skinner ar- to ignore it? The real issue is not the number gues, our ability to report accurately even on this of observers present but whether the report is limited realm must depend on how well we have scientifically useful in predicting behavior, and I learned to match words to internal states, and this shall return to this question shortly. may be far more difficult than we ordinarily sup- pose. The heart of the problem is that for the Skinner's Radical Behaviorism verbal community to train a child in the appro- priate use of words, it must itself know when a A somewhat different position toward introspection particular use is appropriate. In training a child and the mind has been adopted by B. F. Skinner to say apple, for example, the test is relatively (1953, 1963, 1974). Skinner does not deny the easy: Use of the word is reinforced (e.g., praised) existence of mental events, nor does he believe when an apple is present but not when the object that they are inaccessible to scientific analysis is a pear. In the case of internal states, however, ' simply because they are private: "Radical be- it is much more difficult for others to know when haviorism . . . does not insist upon truth by agree- they are present. To cite an example posed by ment and can therefore consider events taking Skinner (1974), how can we teach a child whether place in the private world within the skin. It does he or she is experiencing embarrassment or diffi- not call these events unobservable, and it does not dence? To some extent this problem can be cir- dismiss them as subjective" (Skinner, 1974, p. 16). cumvented by using the situation or the child's Nevertheless, Skinner's position differs sharply behavior as a cue—if someone has just stepped from earlier forms of mentalism in at least two on a sharp nail or is clearly wincing, we may feel crucial respects: relatively confident that they are experiencing pain 1. He regards mental events simply as a form —but Skinner argues that such discriminations are of behavior. In analyzing vision, for example, never likely to be fully accurate. rather than assuming that some inner person— Skinner's arguments on this point have con- the self—is observing a projected image (thus siderable force: Much of our internal world is in- raising the question of what inside the little person accessible, and the correlation between verbal re- allows him or her to see, and so on, in an infinite ports and those states that are accessible is un- regress), Skinner simply interprets seeing as a likely to be perfect. As long as some correlation class of responses, each elicited by a particular set exists, however, such reports may still be useful, of stimuli. Seeing an apple, for example, is one and in some cases these correlations may be very kind of response, seeing an orange, another, and high indeed. We do, after all, converse with each each is assumed to be explicable in terms of the other concerning a wide range of thoughts and same behavioral principles that govern overt forms feelings, and such communications often seem of responding. highly accurate. We may not always be able to 2. While accepting mental events as proper ob- tell the doctor the exact nature of our pain, for jects of study, he does not believe they should be example, but we may still say whether we feel it used in the explanation of other behavior. in our stomach or- in our big toe. Similarly, we Over the years, Skinner has stated his objections can sometimes say with considerable accuracy to the use of introspective data in explaining be- how we feel about political candidates and havior in many forms, but three themes seem to whether or not we intend to vote for them. It is stand out most persistently, and I shall consider important to recognize that such reports may each of them in turn. sometimes be inaccurate or misleading, but it is Skinner's first objection to the use of introspec- equally important to recognize that on other occa- tive reports in scientific explanation is that they sions they may be accurate and reliable. are inherently inaccurate. The nervous system, he Skinner's second objection to the use of mental points out, evolved to deal with biological threats events in explaining behavior is that they are not to survival, and to this end three distinct sensory necessary in a functional analysis. Assume for systems evolved: interoceptive, proprioceptive, and the moment that the mind is the second link in a exteroceptive. The bulk of behavior, however, is three-link causal chain: Changes in the environ- controlled by the neural circuitry of the brain, and ment produce changes in our psychic state, and in this key area there are no receptors. At best, these changes in turn produce changes in our be- therefore, introspection is limited to a tiny fraction havior. If our goal is to be able to practically

AMERICAN PSYCHOLOGIST • APRIL 1979 • 323 modify behavior, Skinner argues, then we must have in a given situation, we would presumably know how behavior is related to the first link in have to know not only all the relevant laws of this chain: the genetic and environmental condi- behavior but also all the relevant aspects of the tions that ultimately control behavior. If we al- individual's past experience. Is this really likely? ready know the relationships between the first and Suppose, for example, that we wanted to know the third links, however, then why bother with whether Rachlin's factory worker was going to the second: quit his job at 9:00 tomorrow. Is it really likely Unless there is a weak spot in our causal chain so that that we will ever know enough about worker psy- this second link is not lawfully determined by the first, chology and all the factors in a particular in- or the third by the second, then the first and third links dividual's past history to predict not only whether must be lawfully related. If we must always go back he or she will quit but when? Might it not be beyond the second link for prediction and control, we may avoid many exhausting and tiresome digressions by much simpler to just ask the worker? Or, to take examining the third link as a function of the first. Valid another example, consider voting behavior: By information about the second link may throw light upon asking voters about their intentions, opinion polls this relationship but can in no way alter it. (Skinner 1953, p. 35) can now generally predict election results with an error of only \% or 2%. Would any social sci- A similar view has been expressed even more entist be likely to do nearly as well if he or she forcefully by Howard Rachlin, a one-time student had to rely solely on knowledge of the environ- of Skinner and the author of an influential intro- mental .conditions that presumably determine voter ductory text, Introduction to Modern Behaviorism. behavior? At least for the foreseeable future, it is In a theoretical article concerning mechanisms of difficult to see how any effective analysis of be- self-control, Rachlin (1974) argued that analysis havior will be able to bypass information about in terms of internal processes is unnecessary, since the second link in Skinner's causal chain. all behavior must ultimately be explained in terms A related objection raised by Skinner to mental of environmental variables: explanations is that they too easily lead us to a To say that the origin of self-control is not in the self is preoccupation with the mind and thus to a neglect not to say that the organism has no properties or has of the environmental factors that ultimately con- been subtracted out of consideration. The biological prop- erties of the organism determine which environmental trol behavior. If we attribute someone's drinking events control which behavioral events. What has been to his or her thirst, for example, Skinner argues subtracted out are those psychological (as opposed to that all too often we are tempted to stop at this biological) properties of the organism such as memory, expectancy, response strength, etc. which serve only to point and thus to ignore the environmental condi- bridge temporal gaps. ... If a man is stabbed and he tions that produce the thirst. To the extent that bleeds, no one will be tempted to talk about memory of this occurs, of course, we will not discover the the stabbing and response strength of the bleeding inter- vening between stabbing and bleeding, although the prop- crucial variables in the environment and hence will erties of his body determined that he would bleed when be handicapped in any later effort at practical stabbed. But for temporally extended events such as his control. dissatisfaction with a bad job, traditional psychological analysis will invoke memory, expectancy and response Such tendencies certainly exist, among current strength in order to bring the cause and effect into im- psychologists as well as past ones. Thus, although mediate temporal proximity. It is certainly something Freudian psychology is often cited as the most about the man that reacts to the long hours, the low pay, the hostile boss, etc., by complaining, going on strike or glaring example of this tendency, the inclination quitting. But it is nevertheless these temporally extended can also be seen in the enormous effort devoted by events that cause his behavior and not his immediate attitude theorists to developing elaborate ques- memories, expectations, and response strengths, (p. 99) tionnaires to measure attitudes while they largely As a desirable goal, we may fully sympathize ignore whether the attitudes so measured have any with Skinner's and Rachlin's arguments: If be- predictive relation to behavior. In a famous study havior could be fully predicted from observable by La Pierre (1934), for example, he accompanied conditions of environment, then why bother with a Chinese couple to 250 hotels and restaurants the inherently messy conditions of the mind? But and found that they were refused admission only is this assumption correct? Can we really predict once. When he later sent a questionnaire to these behavior solely from our knowledge of an individ- same establishments, however, he found that more ual's past experience and current conditions? Even than 90% of them said they would not serve at a theoretical level, this is simply not obvious. Chinese. McGuire (1969), summarizing this liter- To predict accurately how an individual will be- ature, concluded that "the person's verbal report

324 • APRIL 1979 • AMERICAN PSYCHOLOGIST of his attitude has a rather low correlation with attention, however, there has been renewed interest his actual behavior toward the object of the atti- in the extent to which subjects' reports provide tude" (p. 156), and a similar conclusion was reliable information about the nature of these reached by Wicker (1969). Whatever the truth processes. One relevant set of evidence involves to this conclusion (for one dissenting view, see studies in which introspective reports have been Dillehay, 1973), it is clear that considerably more used at a relatively informal, anecdotal level in effort has been devoted to measuring attitudes order to identify potentially interesting phenom- than to determining their usefulness in predicting ena. One striking example of this heuristic func- behavior. tion has been the burgeoning research over the last Again, therefore, we may sympathize with Skin- decade on the value of mnemonic devices in facili- ner's concerns. The fact that a certain line of tating memory. investigation poses dangers, however, is not nor- In the mnemonic technique known as the method mally considered a sufficient reason for ignoring it. of loci, for example, subjects are given a list of Atomic reactions are also potentially dangerous— objects to memorize and are told to do so by exposure to radiation, after all, poses risks more imagining taking a walk along a familiar path lethal than mere speculation about the mind— and observing each of the objects at some point but this has hardly led physicists to the conclusion along the path. Accounts of the effectiveness of that such reactions should be ignored. Rather, this technique go back at least as far as the an- physicists have had to weigh the potential dangers cient Greeks (see Yates, 1966), but for many of atomic research against the benefits that might years they were completely ignored by psycholo- be gained, and in this particular case, they have gists, presumably because of their mentalistic taint. found the balance to overwhelmingly favor con- Once psychologists began to take these reports tinued research. Similarly in the case of intro- seriously, however, controlled experimentation spection, in order to evaluate its usefulness we quickly confirmed the validity of these claims. In need to take into account not only its potential an experiment by Groriinger (1971), for example, costs but also its potential benefits. It is to this one group of subjects were instructed to memorize question—the possible benefits from introspection a list of 25 words using the method of loci, while —that I now turn. a second group were simply given the words and told to remember them using any technique they The Empirical Value of Introspection wished. When tested 1 week later, the experi- Do introspective reports of a person's thoughts or mental group still recalled 92% of the words, and feelings have any value in predicting his or her the control group could recall only 64%. When behavior? At least insofar as everyday life is tested after 5 weeks, recall for the control group concerned, the answer is self-evident. Whether, had dropped to 36%, while that for the experi- we are trying to determine how people will vote, mental group was still at 80%. Introspective re- where they will go on vacations, or the sources of ports of the effectiveness of this technique, in other their phobic reactions, it is clear that one of the words, were strongly confirmed, and similar sup- major sources of information for predicting (and port has come from other studies (e.g., Bower, thus potentially modifying) behavior are people's 1970). introspective reports. We can, of course, choose Insofar as introspective reports have been used to label such reports as rather as an informal source of ideas, then, they have than as , but there should be no successfully pointed to a number of important doubt that we are dealing with exactly the same phenomena (see also Bainbridge, 1974; Montague, class of behaviors so carefully studied by classical 1972; Newell & Simon, 1972). A second, some- introspections and, presumably, condemned by what more direct approach to assessing the pre- early behaviorists. dictive value of such reports has been to observe If we turn to the laboratory for confirmation the extent to which a subject's introspections ac- of introspection's value, however, information sud- curately predict his or her own subsequent be- denly becomes harder to come by. Due in large havior. One example of this approach comes from measure to the methodological heritage of be- recent research into the mechanisms of concept haviorism, introspective data were largely ignored formation. for many years. With the recent explosion of in- Inspired in part by Harlow's research on learn- terest in cognitive processes such as memory and ing set in monkeys, a number of theorists have

AMERICAN PSYCHOLOGIST • APRIL 1979 • 325 proposed that subjects in discrimination tasks do the most important tasks facing memory research- not learn about all stimuli present on a reinforced ers was clearly to develop techniques for moni- trial but rather form hypotheses about the correct toring the frequency of rehearsal, and a number stimulus and then learn only about the particular of possibilities were soon suggested. hypothesis they are testing. To predict the course Suppose, for example, that a set of letters was of learning, therefore, it is necessary to know what presented to a subject, and he or she was then hypothesis a subject is likely to be testing on any asked to recall them 18 sec later. One method given trial, and to this end Levine (1966) pio- suggested for controlling the amount of rehearsal neered a probe technique in which a series of blank during the intervening period was to vary the dif- trials, without any feedback about success or fail- ficulty of the task performed by the subject during ure, were interspersed among learning trials. If the interval: The more difficult the task, the less a subject retains the same hypothesis until he or processing capacity would presumably be avail- she receives either positive or negative feedback, able for rehearsal (Peterson, 1969). Alterna- the subject's responding may be assumed to be tively, the frequency of rehearsal during this in- guided by the same hypothesis throughout the terval could be inferred from the quality of per- series of probe trials, and thus the pattern of re- formance on the intervening task: The worse the sponses shown over a series of trials with different performance, the more effort the subject had pre- stimulus arrangements can be used to estimate the sumably been devoting to rehearsal (e.g., Johnson, nature of this hypothesis. Greenberg, Fisher, & Martin, 1970). Kroll and Levine found that this use of blank trials Kellicutt, however, tried a more direct approach: allowed him to predict many aspects of concept They simply asked their subjects how much they learning with considerable accuracy. On the other were rehearsing during the interval. Specifically, hand, it was a lengthy and exhausting technique using a technique first developed by Montague, for both experimenter and subject, requiring five Hillix, Kiess, and Harris (1970), they provided times as many trials as in normal experiments, their subjects with a button and asked them to thus making it unsuitable for some subject popu- push it whenever they rehearsed the target lations, such as young children. Karpf and Le- material. vine (1971) therefore suggested a new technique One reasonable expectation was that this tech- for determining a subject's hypothesis. They nique would prove a total failure, since rehearsal termed this the introtact, and it consisted simply was a fundamentally unconscious process and thus of asking the subject before every trial what his not amenable to introspective analysis. In fact, or her hypothesis was! They found that this however, the number of reported rehearsals proved questioning procedure did not disturb the learning a highly accurate predictor of subsequent recall, process: Questioned subjects learned at the same with correlations ranging from .93 to .97 across rate as did unquestioned controls and generally the four conditions of the experiment (see Figure showed similar patterns of behavior. Furthermore, 1). Indeed, the predictions of recall based on the data obtained for the questioned subjects were this direct measure proved to be considerably more virtually identical to those obtained from the probe accurate than those based on indirect ones. In technique, so that they were able to predict per- one of the experimental conditions, for example, formance with equal success and in only a frac- subjects were asked to count backward by sevens tion of the time (see also Phillips & Levine, 1975). during the retention interval, and the number of This result has since been replicated in other lab- completed counts was recorded, as well as the oratories and found to account for an impressive number of button pushes. According to the anal- proportion of the variance in trial-to-trial results ysis sketched above, the more subjects rehearsed (Spiker& Cantor, 1977). the target material, the more difficulty they should A second illustration of the potential value of have had in counting backward accurately, so that introspection comes from an experiment by Kroll the number of completed counts would be an and Kellicutt (1972) on the role of rehearsal in accurate guide to rehearsals. In fact, however, verbal memory. According to a highly influential the correlation between completed counts and TC- model put forward by Atkinson and Shiffrin call proved to be only .30, whereas that between (1968), the critical variable in determining whether button pushes and recall in this same condition verbal material will be recalled is how often it is was .94! Thus, although estimates of rehearsal rehearsed when it is first presented. If so, one of based on introspection are inherently more sub-

326 • APRIL 1979 • AMERICAN PSYCHOLOGIST jective than those based on visible behavior, at Reported imagery PA learning least in some situations they may also be consider- ably more accurate (see also Kroll, Kellicutt, & Parks, 1975). For a final illustration of the potential value of introspection in helping us to predict behavior, we I may again turn to research on the role of imagery in memory. In a series of experiments, Allan Paivio (1971) and his colleagues found that con- crete nouns were much easier to remember than abstract ones. The reasons for this difference, 2 2 Trial Trial V'=1J.»R+7».I Figure 2. Mean number of word pairs for which . VISUAL images were reported, and mean number of words 0 AUDITORY recalled, as a function of trials. The four experi- SO 4 X3 R-fll.J mental conditions differed in whether the first and . X7 second members of each word pair were concrete (C) or abstract (A) nouns. (Adapted from Paivio and Yuille, 1969.)

60 Paivio argued, were that concrete nouns were much more likely to elicit visual images and that the formation of such images significantly facilitated recall. Paivio designed a number of experiments se to test this prediction, and on the whole they were 40 highly successful—with one glaring exception. In UJ ' = 7.1R + IM a study by Paivio and Yuille (1967), subjects were given a list of paired associates to learn (that is, a list of word pairs where the subject's task was 20 to recall the second when given the first), with one group instructed to remember the pairs by forming an image of the objects involved (e.g., a man standing on a piggy bank), or by inventing a sentence or phrase involving the two words (e.g., 0123454 "The man went to the bank"). According to REPORTED REHEARSALS Paivio's analysis, the group instructed to use Figure 1. Percentage of trials on which trigrams imagery should have been significantly more likely were recalled perfectly as a function of the number of to recall the pairs (at least insofar as they in- rehearsals reported on those trials. The different func- volved concrete nouns), but in fact no difference tions represent the four experimental conditions, which was observed between the groups. differed in whether subjects were required to count One possibility was that Paivio's imagery hy- backward during the retention interval or to shadow a pothesis was wrong: Whatever the reason for con- list of letters read aloud. To vary the difficulty of crete nouns being easier to learn than abstract these tasks, subjects in the counting task were required ones, it had nothing to do with the formation of to count backward by either threes (X3) or sevens images. Another possibility, however, was that (X7), and subjects in the shadowing task were pre- the subjects simply had not followed their instruc- sented with trigrams in either the same modality as tions! Thus, even though the subjects in the ver- the material to be shadowed (A = auditory) or a bal-mediation group had been told to form sen- different one (V = visual). (From "Short-Term Re- call as a Function of Covert Rehearsal and of Inter- tences, perhaps when presented with the material vening Task" by N. E. A. Kroll and M. H. Kellicutt, they had realized the difficulty of this technique Journal of Verbal Learning and Verbal Behavior, 1972, and so quickly switched over to imagery. In order 11, 196-204. Copyright 1972 by Academic Press, Inc. to evaluate this possibility, Paivio and Yuille Reprinted by permission.) (1969) repeated their earlier experiment but asked

AMERICAN PSYCHOLOGIST • APRIL 1979 • 327 their subjects at the end of each trial what strategy are perfectly willing to use introspective reports, it they had actually used. Subjects in the imagery seems fair to note that by and large, behaviorists group reported a strong tendency to use imagery, have not exactly been in the forefront of research but so did the subjects in the verbal-mediation in this area. Indeed, I argue below that this re- group, and in both cases the tendency to use luctance to use introspection is an inevitable out- imagery increased significantly over trials. Fur- growth of behaviorism's position on the mind: So thermore, this increase in the use of imagery long as the mind itself is viewed with suspicion, proved to be highly correlated with the changes in then any behavior that purports to report on the recall over these trials (Figure 2). The best pre- operations of this mind will also be viewed with dictor of performance, in other words, was not the suspicion. strategy subjects were instructed to use, but the Why, then, have behaviorists viewed the mind one they reported having actually used (see also with such suspicion? One reason has undoubtedly Paivio, Smythe, & Yuille, 1968). been the strong influence of operationalism, or logi- In a number of different settings, therefore, sub- cal positivism. According to this view, for any jects' reports of their hypotheses and strategies statement to be admissible within science, it must have proved to be highly correlated with their have empirical import; that is, it must lead to subsequent behavior and, indeed, have often proved testable predictions. After all, if there is no pos- to be by far the most accurate predictors avail- sible way of determining whether a particular as- able. It would be foolish, of course, to claim that sumption is true or false, what possible purpose introspective reports would always be this reli- can be served by including it within a theory? able—The history of classical introspection has At best it would serve no function; at worst it clearly shown that they are not. That same his- would become a focus for unresolvable controversy. tory, however, makes it equally clear that certain In atomic physics, for example, the electron may kinds of reports are useful. Indeed, it is interest- be regarded as a hypothetical construct, an imagi- ing to note that Skinner himself, though still pre- nary particle that may usefully be assigned certain ferring a functional analysis, has recently become properties within the context of a particular theory increasingly explicit in his acknowledgment of the but whose actual existence can never be evaluated. potential usefulness of introspection: Our theories about electrons can be tested—are What a person feels is a product of the contingencies of the predictions they make accurate?—but the ques- which his future behavior will also be a function, and tion of whether the electron itself really exists there is therefore a useful connection between feelings and can never be directly answered. Applying this behavior. It would be foolish to rule out the knowledge a person has of his current condition or the uses to which analysis to psychology, it has been argued that it may be put. (Skinner, 1974, p. 209) the mind occupies a position analogous to that of the electron: an invisible entity whose states Introspection and the Mind can never be directly observed by outside ob- Until this point my argument has been that in- servers. trospective reports can be of substantial empirical The heart of this argument is that statements value and deserve a more prominent place in the whose validity cannot be tested are scientifically methodology of psychological research than they meaningless and should thus be avoided. As have hitherto enjoyed. Some behaviorists, how- reasonable as this argument may be, however, it ever, might reply that they were by no means is not a completely accurate description of how opposed to this: So long as introspective reports scientists in other disciplines actually behave. are regarded as objectively observable behavior Thus, although it is true that some untestable as- (verbal reports), they have absolutely no objection sumptions have been rejected as scientifically to using one bit of behavior in order to predict meaningless—there is no way of producing de- another. Their only objection, they might go on, cisive evidence either for or against the existence would be to the assumption that this verbal report of God, for example, and this question has there- in some way reflected the operation of an inner fore been considered beyond the realm of science mental state. —it is by no means the case that all unprovable In dealing with this hypothetical reply, we assumptions have been treated in this way. Some might first question whether it is a completely universally shared assumptions about the nature accurate description of the behaviorists' own be- of reality have always been accepted as basic havior. Thus although our behaviorists say they givens, and they have remained unchanged re-

328 • APRIL 1979 • AMERICAN PSYCHOLOGIST gardless of how often the theories in which they because its detection may require the aid of a are embedded have been modified. Newton's the- magnifying glass, or of an amoeba because it can ory of gravity, for example, might have proven a only be seen through a microscope? On the other disastrous failure, but this would not have changed hand, if we once admit that vision can be magni- in any way the reality status accorded to the fied with the aid of artificial instruments, then on objects of this theory: the sun and the planets, the what grounds will we allow light microscopes (and moon and the waves. These phenomena have hence amoebas) but deny electron microscopes always been accepted as fundamental givens, the (and hence DNA molecules)? And if we admit starting points from which all scientific theories electron microscopes and DNA, then on what must begin. It is true that the moon, say, could grounds will we reject cloud chambers and elec- be regarded as only a hypothetical construct, an trons? imaginary entity that we find convenient to postu- The dividing line between real and hypothetical, late within our theories, but physicists have not then, is partly a matter of convention, for scien- seen any value to such a position and have found tists to draw wherever they find it most convenient. it far more convenient simply to accept the evi- A hundred years ago, DNA was unheard of; now, dence of their senses, insofar as it was not contra- to many scientists, it is a proven fact of existence dicted by other facts. Thus, although one could (see also Hempel, 1966; Nagel, 1961). The ques- in principle adopt a position of total skepticism— tion of whether the mind is real cannot therefore nothing really exists, it is all in the mind (!)— be settled by appeal to any absolute criteria but in fact physicists have not done so, and certain depends on the usefulness of such an assumption obvious phenomena have simply been accepted as to the scientists concerned. For the physicist, the real. assumption that the moon is real accords with the If psychological practice is to be founded on an perception of all observers and is not contradicted analogy with physics, then, it might be more ap- by any known data. If the assumption of its exis- propriate to regard the-mind as being parallel to tence is therefore universally shared and does no an object that can be seen, such as the moon, harm, then why insist on its being treated as rather than a hypothetical one such as an electron. hypothetical? In a real sense, after all, we do see the mind, or at In the case of the mind, on the other hand, be- any rate its contents: We may perceive a pain in haviorists have argued that scientific acceptance our big toe, for example, just as vividly, if not of its existence would be harmful. Above all, they more so, as we see the moon on a foggy night. have suggested, any formal acceptance of the mind Both perceptions may be misleading in relation to would lead to an inevitable increase in the tend- some external or logical reality—physical measure- ency to attribute behavior to mental states, with ments tell us that the moon when glimpsed at the a concomitant decrease in the analysis of the en- horizon may not be nearly as big as it appears; vironmental variables of which these states are the pain in our big toe may still be felt even after a function. This argument, I believe, deserves to the offending digit has been amputated—but as be taken seriously: It is all too easy to attribute perceptions, both are equally real. behavior to some hypothetical inner state and then Even if this appeal to naive realism were to be to conclude complacently that the behavior has rejected—that is, even if it were insisted that the therefore been explained. On the other hand, the mind cannot be perceived directly and so should chances of this happening may now be consider- more appropriately be regarded as analogous to ably smaller than when the doctrine of behaviorism the electron than to the moon—this would still not was first being promulgated. At that time the establish that the mind was imaginary, for the practical results of a behavioral analysis were at simple reason that many physicists and philoso- best only a distant shadow on the horizon, so if phers believe that the electron is also real! Con- psychologists were to be shielded from distraction sider, for example, the following set of objects: as they soldiered on, the only effective prophylaxis the moon, a speck of dust, an amoeba, a DNA may well have been a rejection of the mind in its molecule, and an electron. How are we to decide entirety. Given the substantial progress that has which, if any, are real and which are hypothetical? been made in the intervening decades, however, We might naively argue that only those things and the extent to which the value of a behavioral are real that can be seen with the naked eye, but analysis is now widely accepted (see, e.g., Leiten- are we really prepared to reject the reality of dust berg, 1976b), it may no longer be necessary to

AMERICAN PSYCHOLOGIST • APRIL 1979 • 329 reject other avenues of investigation quite so To take another example, consider an article rigidly. The very success of behaviorism, in other published in Psychological Review by Stoyva and words, may mean that we no longer need to take Kamiya (1968) concerning the psychological status all its arguments quite so seriously! of dreams. The authors presented a lucid review In any case, whatever the extent to which this of the literature on dreaming and of the extent to danger remains real, it needs to be weighed against which subjective reports of dreaming during sleep the advantages that full acceptance of the mind's have been found to be correlated with a variety of reality might bring. Most obviously, franker ac- electrophysiological measures, such as changes in ceptance of the mind might help to remove a long- brain waves, and rapid eye movements (REMs). standing source of tension from within our disci- Indeed, changes in these physiological states have pline: the sometimes flagrant contradiction be- been found to be correlated not only with the tween our actual behavior and our post hoc at- occurrence of dreams but even with their precise tempts at its scientific rationalization. Consider, content. One subject, for example, reported hav- for example, the dilemma facing any behaviorally ing dreamed of watching someone walking up a oriented therapist. In order to select the appro- staircase, and examination of his eye-movement priate treatment for a particular patient, the thera- record showed that his eyes had in fact moved in pist obviously needs to interview him or her in the highly stereotyped (and unusual) up-and-down some detail concerning the nature of his or her pattern appropriate to walking up stairs (Dement problem. If, however, introspective reports are & Kleitman, 1957). Rather than interpreting this only a form of verbal behavior, on what basis does evidence as support for the reality of dreams, how- the therapist decide that one bit of verbal behavior ever, Stoyva and Kamiya suggested that dreams will be more revealing than another; that is, how should be regarded as hypothetical constructs, does the therapist decide what questions to ask? using electrophysiological measures as tests of the And in evaluating the patient's answers to poten- theory's validity. As I suggested above, this in- tially painful questions, how does the therapist terpretation is certainly possible, but is it really decide whether the patient was really telling- the an accurate reflection of what the psychologists in- truth? volved were actually doing? Suppose, for example, If an introspective report is only behavior, then that REMs or brain waves had proven not to be it has been lawfully determined by past experience, correlated with subjective reports of dreaming. and it makes no sense to ask whether it is honest, Would the experimenters in this area have aban- any more than it would make sense to ask whether doned their theories and concluded that dreams a blink of the eye is honest. In trying to deter- did not exist? Or would they simply have pushed mine whether a patient is accurately reporting his on, accepting that dreams exist just as physicists or her feelings, the therapist is clearly not treating accept that planets do, and looking for some other the patient's introspective report as an arbitrary physiological correlate of this basic phenomeno- bit of behavior but is assuming that the patient logical fact? does have certain internal thoughts and feelings Instead of trying to force our behavior into the and is questioning the correlation between these in- Procrustean bed prescribed by theory, I believe it ternal states and the external report. It is cer- would be far less taxing, as well as more honest, tainly possible for the therapist later to explain to accept overtly what we so clearly believe in his or her behavior in different terms—the pa- covertly. Not only might this position reduce tient's fears were only a hypothetical construct or, some of the mental gymnastics now required of by definition, consisted only of overt behaviors behaviorally oriented psychologists, it might also such as sweating or trembling—but it seems highly help to eliminate some of the unnecessary con- doubtful that the therapist's actual choice of ques- flicts that now exist between clinic and laboratory tions was in any way guided by these assumptions. (not to mention teacher and student!). A more plausible construction is that the therapist brought to the interview a whole set of intuitive A second unfortunate heritage of behaviorism assumptions about the nature of emotions and their has been a widespread reluctance to obtain intro- relation to behavior, and that it was these intui- spective data, even in situations where they might tions, based in large part on the therapist's own be of considerable value. This reluctance is most introspective experience, that actually guided his obvious in behaviorally oriented areas such as be- or her questioning (see also Locke, 1971). havior therapy, where experimenters have tended

330 • APRIL 1979 • AMERICAN PSYCHOLOGIST largely to ignore patients' thoughts and feelings, ance (see, e.g., Dweck & Gilliard, 1975)—but even where these are nominally the primary focus why did no one even try? of the therapy. Perhaps the clearest example of A number of other examples could be given, but this ambivalence comes from the clinical therapy perhaps just one more will suffice. Mischel (1974) of systematic desensitization, which has proven to summarized a brilliant series of experiments he be a highly effective treatment for phobias (see, and his colleagues conducted to investigate the e.g., Leitenberg, 1976a). If a patient was afraid processes by which children learn to tolerate delays of snakes, for example, he or she would be asked to in gratification. If, for example, children are visualize a mildly frightening scene involving given a choice between one marshmallow immedi- snakes while simultaneously relaxing his or her ately versus two in 20 minutes, it turns out that body. Once the patient was able to visualize this their ability to endure the frustrating delay is dra- scene without fear, he or she would then be asked matically affected by the way they think about to imagine a slightly more frightening one, and so marshmallows during the delay period. Children on, until eventually the fear of snakes had dis- who imagined them as soft and chewy, for ex- appeared altogether. Now the imagery formed by ample, could wait for an average of only 5 minutes the patient is clearly at the heart of the treatment, before asking for the immediate reward, whereas but until very recently (e.g., Kazdin, 197S; Wade, children who imagined them as fluffy white clouds Malloy, & Proctor, 1977) there have been almost could wait almost three times as long (Mischel & no attempts to examine the nature of the images Baker, 197S). It is striking, however, that formed by different patients and the extent to throughout his studies, Mischel manipulated im- which their content and vividness may be corre- ages solely via the instructions he gave his sub- lated with the eventual outcome of the therapy. jects: "When you look at marshmallows think To be sure, these variables might ultimately prove about how light and puffy they are." (Mischel & of little importance, but the failure even to look at Baker, 1975, p. 257); at least in his published them, in what is otherwise one of the most in- reports, he never systematically interviewed his tensively studied therapies of all time, is striking. subjects to find out what images they actually used If this reluctance to obtain introspective data and the extent to which these different images is most obvious in behaviorally oriented areas such helped or hindered resistance to temptation. as systematic desensitization, it is by no means This continuing failure to obtain and report confined to these areas. Thus, although cognitive introspective data—even when the phenomena un- psychologists have proven far more willing to em- der study are hypotheses and images—appears to brace mental phenomena such as memory and at- reflect the continuing suspicion with which many tention, they too have sometimes been hesitant psychologists, from all areas, still approach the to use introspection in studying these processes, mind. Thus, although methodological behaviorism preferring instead to rely on inferences from purely allows introspective data—its only caveats concern behavioral observations. One example of this the relation of the obtained verbal behavior to a tendency I have already discussed concerns re- hypothetical inner state—so long as introspective search into concept formation, where for many reports are regarded as being of "equivocal status" years psychologists interested in the nature of hy- (Kanfer, 1968), psychologists seem unlikely to potheses rarely made any attempt to ask subjects venture near this treacherous terrain. After all, directly what hypotheses they were using, pre- if introspective reports correspond to no inner ferring instead to infer these hypotheses from per- reality, if they are regarded as only one more bit formance on a series of special test trials. Phillips of behavior, then why should psychologists make and Levine (197S) eventually showed that direct any serious attempt to study them, especially questioning offered some potentially significant when the universally acknowledged limitations of advantages, but it is striking that it should have introspection are taken into account? If the exis- taken so many years before anyone thought to tence of the mind were accepted more openly, on evaluate experimentally the potential of this tech- the other hand, it seems likely that psychologists nique. To be sure, there were valid grounds for would become far more willing to study intro- suspecting that it would not work—for example, spection experimentally, so that we could begin that the hypotheses involved might not be con- to distinguish more clearly those situations in scious, or that interrupting subjects with questions which introspective reports were likely to be useful might distract them and thus alter their perform- from those in which they were not.

AMERICAN PSYCHOLOGIST • APRIL 1979 • 331 Summary and Conclusions awareness) but in its accuracy. In some cases, this may be because of the subject's limited ability In effect, the position advocated here represents a to discriminate among internal states; in others, selective mixture of behaviorism and introspection- because of forgetting, or even dishonesty. And ism. From behaviorism, I would retain Watson's in some cases, rather than directly reporting ob- revolutionary emphasis on the practical modifica- servations of their thoughts or feelings ("I felt tion of behavior as the proper goal of psychology. angry"; "I intend to vote for X"), subjects may The ultimate criterion for evaluating any line of report inferences from such data ("I hit him be- research, therefore, must be its success in con- cause I was angry"; "I prefer X because he is tributing to the prediction and control of overt handsome"); such inferences about our own be- behavior. I would argue, however, that introspec- havior may be just as erroneous as our inferences tion can play a powerful role in contributing to and judgments about other matters (see especially this goal. As shown by both classical and modern Nisbett & Wilson, 1977). Even if we accept cer- research, introspective data can be highly reliable tain mental states as real, therefore, we cannot and useful, helping not only to predict specific be- accept particular verbal reports of them as neces- haviors but to discover fundamental principles of sarily being accurate. Wherever possible, we need learning and performance (e.g., Weber's law, and to supplement verbal reports with other circum- the role of imagery in verbal memory). Rather stantial or behavioral evidence, and the ultimate than rejecting introspection indiscriminately, there- criterion for evaluating any form of introspective fore, a far more productive strategy might be to data must be their usefulness in predicting future identify systematically the conditions under which behavior. Assuming that this criterion can be it is most likely to prove useful. satisfied in particular instances, however, it would With regard to the mind itself, I have argued seem foolish to continue to ignore such data. that formal acceptance of its reality would not The overriding concern of this article, then, has only not violate any of the accepted canons of been with how best to advance our ability to pre- scientific methodology but would also offer a dict and control behavior, and greater acceptance number of potentially profound advantages, rang- of introspection and the mind has been advocated ing from a diminution in the unnecessary tensions in the belief that it can make a significant, albeit within our discipline to the discovery of new prin- limited, contribution to this goal. In the words ciples of behavior. Against these potential advan- of the biologist Seymour Kety (1960): tages must be weighed the possibility of other, rather less desirable consequences, including in [To deny] the existence or the importance of mental particular a proliferation of untestable theories states merely because they are difficult to measure or because they cannot be directly observed in others is and sterile controversies. There is no easy formula needlessly to restrict the field of the mental sciences and for predicting which of these outcomes, beneficial to curtail the opportunities for the discovery of new or harmful, would prove more likely in the long relationships. The remarkable hallucinogenic properties of lysergic acid diethylamide (LSD) are barely hinted at run, so that it would probably be beneficial for in behavior, and the behavioral disturbances in schizo- psychologists on both sides of this issue to state phrenia are a mere fragment of the entire picture. Nature their positions with some degree of humility. Given is an elusive quarry, and it is foolhardy to pursue her with one eye closed and one foot hobbled, (p. 1862) the increase in psychology's maturity and sophis- tication, however—due in no small part to the in- REFERENCE NOTES fluence of behaviorists such as Watson, Tolman, 1. Cohen, W. Form recognition, spatial orientation, per- and Skinner—I believe that the dangers of mis- ception of movement in the uniform visual field. In guided mentalism have now receded considerably, A. Morris & E. P. Home (Eds.), Visual search tech- so that the balance of arguments now strongly niques (Pub. No. 712). Washington, D.C.: National Academy of Sciences—National Research Council, 1960. favors a more positive attitude not only to the 2. Tepas, D. I. The electrophysiological correlates of mind's existence but to its experimental investiga- vision in a uniform visual field. In M. A. Whitcomb tion. (Ed.), Visual problems of the armed forces. 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