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6 Altering Mental States The relation between mental states and performance has received considerable attention in scientific and popular writings and therefore came under the committee's scrutiny. There is little doubt that our internal states fluctuate during the course of a day and with different activities. Just how these changes influence performance is less clear. This chapter reveals some shortcomings in the idea of an optimal state for all performances: recent work suggests the existence of more complex ~ _, , it, . ., _, . , __ processes involving cortical system computations. Further understanding of these processes should have implications for the way in which various techniques for altering states may affect performance. The idea of brain asymmetry and hemispheric specialization has received considerable attention in recent years by both researchers and practitioners. Despite a history of claims to the contrary, the committee found no evidence that links performance or learning to differences in function between the brain hemispheres. This conclusion is based on the subcommittee's review of literature, which was aided considerably by the availability of an earlier review undertaken by Davidoff and his collaborators (1985~. Practical applications have been derived from the assumption of a relation between specialized functions and performance. This assumption is the basis for techniques that claim to enhance different kinds of performances by increasing information-processing functions. The committee evaluates a technique that presents material to the two hemispheres in order to integrate hemispheric activity. 102
ALTERING MENTAL STATES 103 ALTERING MENTAL STATES FOR PEAK PERFORMANCE There seems to be little doubt that mental state can greatly influence one's ability to perform both physical and mental tasks. The idea that people can achieve an internal state that will be optimal for a broad range of performance has been an appealing one. Typically it has been assumed that there is an optimal level of arousal for performance of a given complexity (Duffy, 1962; Yerkes and Dodson, 19081. Usually the concept of arousal is thought of as an element of stress; there is associated with any level of stress some particular arousal level. According to this view, simple tasks require a high state of arousal in order to maintain alertness; complex tasks require a lower state of arousal in order to reduce reliance on stereotyped or overlearned responses, which tend to dominate when arousal is high (Easterbrook, 19591. This argument has been used to support the idea of an optimal level of arousal that is reduced as task complexity increases. The optimal arousal concept fits with behavior theories that were popular in the 1950s. These theories required a source of energy or drive to keep the organism active. The discovery of the ascending reticular activating system in the brain (Moruzzi and Magoun, 1949) as a diffuse physiological basis for activating the cortex fostered this conception. As our knowledge of the variety and specificity of neurotransmitter systems has increased (Robbing and Everitt, 1982) and as psychological theories have moved from gross behavior to the study of cognition (Kahneman, 1973), a more complex view of internal states has emerged. We have begun to think of cognition as involving a large number of cortical computations in highly distributed neural systems (Rumelhart and McClelland, 19861. Different transmitter systems serve to modulate these cortical computations in varying ways (Robbing and Everitt, 19821. This underlying complexity makes it much harder to suppose that any training technique will provide optimal conditions for all forms of physical and mental activity. Consider, as an example, the clear changes that seem to take place in one's level of alertness during the course of the day. We often feel at a low level of alertness early in the morning and at a much higher level as the day wears on. Body temperature increases over the course of the day. When alertness is high later in the day, one's speed of responding and sensory thresholds are also improved, but the number of items that can be reported back from memory after a single presentation is reduced (see Posner, 1975, for a review). Several methods have been designed to alter a person's internal state, either through learned forms of self-control or through the control of others. Collectively these methods are said to produce altered states of
104 ENHANCING HUMAN PERf ORMANCE consciousness; they include meditation' hypnosis, relaxation, and bio- feedback. At one level these effects should not be surprising. The internal state of the organism is constantly in flux. It changes with time of day, health, interest level, mental activity, and alertness. Since many of these factors are under voluntary control, it is a relatively easy matter to train people to produce different internal states. These altered internal states do affect physiological processes, including the electrical activity recorded from the scalp and autonomic systems (Tart, 19691. Changes in internal state are also frequently accompanied by subjective reports of feelings of well-being, relaxation, increased concentration, and so on (Tart, 19691. There is also some evidence that differences in internal state may lead to changes in performance. This is particularly true of physical activity. For example, if a person is warned about the occurrence of a signal for which a response is needed, there is a marked change in internal state during the time between the warning and the signal to perform. This change in alertness will lead to more efficient processing than if the person had not been prepared for the signal (Kahneman, 19731. It is also widely believed that the focus of attention during skilled performance is important. During the early phases of skill training, it is useful to concentrate on the skill to be learned, particularly on elements to be imported from already-learned skills (Fists and Posner, 1967~. It is thought that attention serves to aid the transfer of concepts from related skills to the new one. Studies of mental practice confirm the utility of attention to the phases of a skill during learning (see, for example, guided imagery in Chapter 51. There is also evidence that training people to adopt a particular mental state can sometimes produce changes in internal state that, for example, can be measured by EEG and that serve to reduce the usual strong tendency for performance to decline with periods of sustained concentration (Beatty et al., 1974~. These established findings provide little support for the existence of a general state of consciousness that will improve performance over a wide range of skills such as those found in battlefield conditions. Unfortunately, time did not allow the committee to explore the evidence for the wide variety of specific training or induction methods that might provide a basis for technologies for manipulating internal state. The evidence that optimal conditions for rapid responding are different from optimal con- ditions for the best memory performance raises doubts that there is any generally optimal state. The acts involved in thinking about or attending to information themselves seem to change internal state by producing alterations in blood flow, metabolism, and electrical activity (Hillyard and Kutas, 1983; Roland, 1985) within the neural systems most closely related to the focus of thought. These very specific changes during focal mental activity may serve to counteract any general state induced by
ALTERING MENTAL STATES 105 training. Nonetheless, it appears to the committee that the Army might undertake careful literature reviews of links between several technologies for altering internal state (e.g., hypnotism, meditation) and change in performance. There are no theories to date of how modulation of cortical areas by the state of the organism affects the computations performed by these same cortical systems. In the absence of theories that relate computation to state, it is difficult to evaluate claims about how a specific alteration in state will affect performance. The development of knowledge about the relation of changes in state to computation may be the best way to proceed in evaluating claims in this area as well as in fostering future developments in the field. Accordingly, we recommend research support of areas relating changes in state to computation. One area in which computation studies have been undertaken in relation to neural systems is brain asymmetry and hemispheric specialization. The committee devoted considerable time to a consideration of these findings, which are discussed in the next section. BRAIN ASYMMETRY In the last 20 years there has been a dramatic increase in research dealing with the differences in function between the hemispheres of the brain. A substantial body of literature now points to differences in the way the two hemispheres process information, as well as to anatomical, electrophysiological, and metabolic correlates of these functional asym- metries (for reviews, see Bradshaw and Nettleton, 1983; Springer and Deutsch, 1985~. Accompanying this research has been much speculation regarding its implications for enhancing human performance. Among the ideas that have been considered as possible ways to enhance performance are (1) increasing the channel capacity of the brain by presenting stimuli to each hemisphere separately, (2) training individuals to utilize hemi- spheres differentially, (3) selecting individuals for tasks depending on their pattern of hemispheric utilization, and (4) synchronizing the activity of the hemispheres to enable them to work more effectively in concert. In this section we present briefly what is currently known about hemispheric asymmetry of function and consider each of the strategies for application listed above. In each case we evaluate the link between the state of knowledge in the field of hemispheric asymmetry of function and the rationale for the particular approach, as well as the evidence supporting the value of the technique, that is, the empirical evidence for its usefulness. Both approaches are important in assessing the value of a technique. While a technique may prove to be useful in various applications, it may be only weakly tied to a purported underlying
106 ENHANClNC HUMAN PERFORMANCE neurological mechanism. Conversely, a technique may follow directly from research findings and be well-founded in theory, yet it may fail for various reasons to be useful in practice. THE NATURE OF HEMISPHERIC DIFFERENCES Substantial bodies of research with three types of subjects unilaterally brain-injured, commissurotomized, and neurologically normal have con- verged unequivocally on the basic finding that the hemispheres of the brain are functionally asymmetric. Investigators working with unilaterally brain-injured subjects focus on the defects that follow from damage to one hemisphere. Those working with commissurotomized subjects split- brain patients who have had fibers connecting the hemispheres cut for medical reasons compare performance of the two hemispheres by presenting material separately to each one. Testing situations designed to deliver visual, auditory, or tactile material are used for this purpose. Work with neurologically normal subjects uses many of the same approaches as the work with split-brain subjects, although the presence of fibers connecting the hemispheres leads to the prediction that the differences observed will be considerably smaller in magnitude than those found in commissurotomized patients. In addition, several techniques designed to measure ongoing brain activity have been employed by investigators looking for evidence of asymmetries: electrophysiological recordings, regional cerebral blood flow measurements, and positron emission tomography. The most robust differences that have been demonstrated between the hemispheres involve the production and perception of speech and language and visual-spatial processing. which are specializations of the left and right hemispheres, respectively. The left hemisphere, In almost all r~gnt- handed persons and a majority of left-handed persons, has almost exclusive control over expressive language (i.e., speaking and writing) and appears to be superior to the right hemisphere in most aspects of . . A. . .-. . . . _ _ ~_ 1 1 -_ _1~ ~ - speech and language perception as well (Rasmussen and Milner, 1975; Zaidel, 19781. The right hemisphere, in contrast, is superior to the left in tasks with a visual-spatial component (DeRenzi, Faglioni, and Scotti, 1971; Warrington and Rabin, 1970~. Considerable effort has been expended to extend these findings and develop a catalog of other hemispheric differences and to determine what underlying principles may characterize them. The result has been a shift away from an emphasis on the nature of the stimulus as critical in determining differential hemispheric involvement, to an emphasis on the kind of task a subject must perform with a given stimulus. One widely cited but controversial generalization that accounts for a fair number of
ALTERING MENTAL STATES 107 findings is the claim that the left hemisphere is specialized for analytic processing, while the right hemisphere is specialized for holistic processing (Bever' 19751. Following quickly in the wake of research on the nature of hemispheric asymmetry of function has been work dealing with individual differences in the distribution of function between the hemispheres. Handedness and gender, the two variables studied first and most extensively, have both been shown to be related in complex ways to patterns of hemispheric differences (Hardyck and Petrinovich, 1977; McGlone, 19801. Although few persons would dispute the existence of hemispheric differences, it is important to note that there is considerable controversy in the research on brain asymmetry. A frequently occurring problem is failure to replicate findings. Many factors appear to affect the outcome of studies on brain asymmetry, and until we have a good understanding of their effects, replication of experiments can be problematic. Another concern is the looseness in the basic terminology. Hemispheric special- ization is sometimes used to refer to an all-or-none difference between the hemispheres, while in other cases it is assumed that both hemispheres possess the ability to perform a given task but do so in ways that differ qualitatively or quantitatively. The extent to which each hemisphere becomes involved in a given task and in what way are questions asked only infrequently. Most investigators are well aware of these difficulties and the limitations they place on interpretation of research findings. The problems tend to be overlooked, however, by more popular extensions of brain asymmetry findings, and the distinction between what can reasonably be taken as fact and what is speculation is too often blurred. In the sections that follow, this distinction is emphasized. IN FORMATION -PROC ESSING CAPACITY Early work with split-brain patients suggested that each hemisphere could function relatively independently. A task such as a simple visual discrimination could be performed by either hemisphere, as long as an opportunity was provided for the right hemisphere to respond nonverbally by pointing. A hypothesis developing from this finding was that the total processing capacity of the brain might be increased by distributing information between the hemispheres so that each side could operate independently; that is, presenting each hemisphere with a different task might double the brain's capacity to deal with information. The greatest support for this hypothesis was predicted to come from patients with surgically separated hemispheres; less dramatic effects were also predicted for neurologically intact subjects. One experiment required split-brain subjects to pick out target letters
108 ENHANClNC HUMAN PERFORMANCE from an array of alternatives. In one condition, two letters or digits were flashed in one visual field, hence restricting the input to one hemisphere. In the other condition, stimuli were flashed in each visual field simulta- neously, resulting in presentations to both hemispheres. The results did not show an increase in total processing capacity when stimuli were presented to both hemispheres. Performance was generally higher with unilateral presentation; bilateral presentation frequently produced neglect of the stimuli sent to the right hemisphere (Ten" and Sperry, 1973, 19741. More promising findings emerged from another study, in which split- brain patients were compared with normal controls on two simultaneous visual discriminations, one to each hemisphere. While control subjects took considerably longer to respond to two discriminations compared with one' the split-brain patients responded as quickly to two as to one; however, their reaction times were considerably longer than those of the control subjects, making simple interpretation of these findings difficult (Gazzaniga and Sperry, 1966~. More recent work has pointed to the level of difficulty of the simulta- neous tasks as critical in determining the outcome of such studies. It appears that the two hemispheres of the brain act as independent channels only if the tasks are relatively easy and do not require attention from both hemispheres at once. When processing demands are increased, the apparent independence of the hemispheres breaks down, and the advan- tage of separate presentation to each hemisphere is lost (Kreuter, Kinsbourne, and Trevarthen, 19721. Effects with neurologically normal subjects would be expected to be even weaker, since the two hemispheres remain in constant communication at the cortical as well as subcortical levels. Thus there is no evidence at the present time that would suggest that presentation of material separately to each hemisphere would be of practical value in enhancing processing capacity. HEMISPHERICITY The term hemisphericity generally refers to the idea that each person may naturally have a preferred mode of cognitive processing that in turn reflects greater activity of the left or right hemisphere of the brain. Attempts to apply this concept to human performance have involved assessing an individuals particular pattern of hemispheric utilization to permit an appropriate match between the individual's processing style and the tasks that are to be assigned to that person. A related application involves attempts to train hemisphericity, that is, to train an individual to utilize the left or right hemisphere to a greater extent, presumably leading to enhanced performance when an appropriate match between person and task is made.
ALTERING MENTAL STATES 109 The first step in any evaluation of the concept of hemisphericity and its application to performance involves a review of the paradigms used to measure it. Davidoff et al. (1985) cite four approaches lateral eye movements, electrophysiology, cognitive tests, and questionnaires. Lateral eye movements refer to the shift in gaze that occurs when an individual is engaged in cognitive activity. Depending on the nature of the activity, individuals have characteristic and stable patterns of eye movement that have been claimed to reflect hemispheric utilization. A rightward gaze is presumed to reflect greater activity of the left hemi- sphere, while a leftward gaze is seen as evidence of right hemisphere involvement. A thorough review of the eye movement literature by Erlichman and Weinberger (1978), however, concluded that the link between eye movements and hemispheric asymmetry is not well estab- lished. Later work is consistent with this conclusion as well (Beaumont, Young, and McManus, 1984~. With regard to electrophysiological recordings to assess hemisphericity, Davidoffet al. (1985) note that there are serious methodological difficulties associated with their use to measure hemispheric asymmetry. While aware that there is considerable debate among neuropsychologists re- garding the potential of electrophysiological measures of asymmetry, they conclude that no experimental paradigm has yet been established that would permit a reliable index of lateral hemisphere function (of the sort needed to assess hemisphericity) to be derived from EEG or evoked potential recordings. Questionnaires have been the most popular measure of hemisphericity. Typical of the questionnaires currently in use is Your Style of Learning and Thinking (Torrance and Reynolds, 1980), which contains items asking about an individual's preference for different kinds of cognitive activity. Results obtained with this questionnaire correlate with various measures of creativity, reflecting the developers' belief that `'there is considerable evidence to suggest that the essence of creativity is a specialized function of the right hemisphere" (Torrance and Reynolds, 1980:2~. Evaluations by Beaumont, Young, and McManus (1984) and Fitzgerald and Hattie (1983) conclude that these questionnaires are poorly constructed psy- chometrically and weak in their theoretical rationale. Beaumont, Young, and McManus (1984) state that at the present time there is no evidence in the neuropsychological literature to support an association between the right hemisphere and creativity, and hence no basis for the assertion that the questionnaires currently in use can assess the differential contribution of the hemispheres to cognitive function. Nevertheless, such questionnaires continue to be very popular measures of hemisphericity, appearing in the media as well as in various seminars and courses for bus- inesses seeking to make the best possible match between employee and
llo ENHANCING HUMAN PERFORMANCE position. Their appeal is their simplicity, both in administration and scoring. Batteries of cognitive tests have also been used to measure hemispher- icity. As Davidoff et al. (1985) note, a major problem with these tests is the need for independent validation of their relationship to patterns of hemispheric activity. It is often the case that a test is included in a battery because it appears to involve left or right hemisphere skills, although there is no direct, independent determination that it does indeed do so. Thus, a test with a large verbal component may be included to assess involvement of the left hemisphere, although no independent evidence is presented to show this association. A notable exception to this absence of independent validation is the work on the Cognitive Laterality Battery by Gordon (19864. This battery was adapted from tests of brain-damaged patients that were shown to reflect left or right hemisphere abilities. Gordon's initial attempts to use his battery ire an applied setting have met with some success (Gordon, Silverberg-Shalev, and Czernilas, 19821. In particular, he found that combat pilot trainees performed better on tests believed to measure right hemisphere function than did helicopter pilots or navigators. Gordon himself states, however, that . . . while it is true the tests were selected on the basis of hemispheric research . . . the value of the Cognitive Laterality Battery is that it gives information about the relative performance of these specialized hemispheric skills, and does not measure the relative efficiency or activation of the hemispheres themselves. (1986:224) In summary, it would appear that at the present time we do not have the kind of independently validated measures of hemisphericity that would make it a truly useful concept. Such measures may be forthcoming, but they are not here yet. Without such measures it is impossible to answer the questions of whether hemisphericity has important implications for performance. With regard to the related question of training hemispheric involvement, we have no direct evidence that differential hemispheric utilization can be trained. Just as we lack validated measures of hemisphericity, we lack any way to measure the changes in brain hemisphere involvement that are presumed to accompany certain training strategies. As Davidoff et al. (1985) note, cognitive style can probably be affected by training. There is no evidence, however, to show that such modification has a neurological substrate that involves differential utilization of the hemispheres. Such a link may exist; at the present time it has not been demonstrated. SYNCHRONIZING HEMISPHERIC ACTIVITY The notion of increased channel capacity resulting from presentation of material to separate hemispheres is based on the assumption that each
ALTERING MENTAL STATES 111 half of the brain functions independently. Similarly, the concept of hemisphericity emphasizes the differences in function between the hem- ispheres and the value of differential hemispheric involvement. An entirely different approach to brain asymmetry and its relation to human perform- ance stresses the value of having the hemispheres act synchronously. Hemi-Sync~, short for Hemispheric Synchronization, is a patented technique developed by Robert Monroe of the Monroe Institute of Applied Sciences in Faber, Virginia. The process uses the phenomenon of binaural beats "to help create simultaneously an identical wave form in both brain hemispheres." (All quotations are from ''Inquiry, Information, Innova- tion," a Monroe Institute information brochure.) To produce binaural beats, a tone of one frequency is presented to one ear and a tone of a slightly different frequency is presented to the other. Given the proper circumstances, one hears a warbling sound whose frequency is equal to the difference between the original tones. According to the Monroe Institute's literature, "this third signal is not an actual sound, but an electrical signal that can only be created by both brain hemispheres acting and working together, simultaneously. The unique coherent brain state that results is known as Hemispheric Synchronization, or Hemi-Sync~." This identical wave form is believed to assist the user in using "more of his brain power" and to facilitate such diverse activities as sleep, concentration, learning, and surgical recovery because "both hemispheres of the brain can be focused on the same state of awareness at the same time." The evaluation of Hemi-Sync~ by the committee involved a search and review of the literature relevant to its underlying rationale, a review of the extensive material provided by the Monroe Institute and others relating to the anolication of Hemi-Sync~, and a site visit to the Monroe --I ~ r r Institute. The subcommittee toured the facilities and met with Robert Monroe, a staff member, and two professional members of the Institute (a speech pathologist and a clinical psychologist) who use the Hemi- Synct3 tapes in their work. There are three main principles underlying Hemi-Sync~. The first is that presenting two tones of slightly different frequency simultaneously, one to each ear, results in the perception of a third tone as the result of some process involving the two hemispheres. The second principle is that the binaural beat phenomenon results in an alteration of the main frequency component of the EEG such that "frequency following" takes place. The third asserts that certain BEG states facilitate particular types of performance. With regard to the theoretical rationale underlying Hemi-Sync~, the scientific literature suggests that the binaural beat effect is most likely due to binaural interaction at the level of the superior olivary nucleus (Oster, 1973), which means that binaural beats are not a cortical phenom
2 ENHANCING HUMAN PERFORMANCE enon and are not produced by the two hemispheres working in concert. With regard to frequency following, a small literature relevant to this claim was found. Frequency following in the auditory evoked response has been demonstrated with both tone bursts and continuous tones over a range of frequencies from 70 hertz to 1,500 hertz (Glaser et al., 1976~. In addition, frequency following responses to 500-hertz tone bursts presented to the left ear and 540-hertz tone bursts presented to the right ear have been obtained by Hink et al. (1980), demonstrating frequency following to binaural beats under certain conditions. With regard to the third principle, no evidence that frequency following the stimuli employed in Hemi-Sync<3 exists was provided by the Monroe Institute or obtained through a search of the literature. At the site visit, Robert Monroe indicated that the Institute has not focused its efforts on generating the kind of research that would satisfy the criteria for publication in refereed scientific journals. Its emphasis has been on the development of techniques that users find to be beneficial by whatever criteria they personally choose to employ. However, in response to the need of the committee for scientific evidence of the utility of Hemi-Sync~, we were referred to a variety of articles published by members of the Monroe Institute in a newsletter and were given the names of 13 individuals who had reported successful uses in a variety of applications and who could be contacted for further information. Hemi-Sync~ has been claimed to be of value in a wide variety of educational and therapeutic settings O Of greatest interest for purposes of this report are those applications involving human performance. For the sake of completeness we wish to note that material was provided to us documenting its use in pain control in cancer patients and in cases of alcohol abuse, retardation, autism, and seizure disorders. In these instances patients typically listened to Hemi-Sync~ sounds accompanied by music or other stimuli through headphones as part of their therapy. Reports typically took the form of individual case studies or, in some cases, self~reports of beneficial effects. The committee found what came closest to formal research designs in three studies of educational applications. In the first study, Hemi-Sync~ was employed with students in the basic broadcasting course at the Defense Information School to determine its effects in enhancing per- formance and inducing relaxation. The study employed a variety of tapes using Hemi-Sync~ sounds listened to individually through headphones during a ten-week course by 22 subjects whose performance was compared with that of a previous class not using the tapes. Self-reports of stress level and motivation throughout the study, as well as the students' assessment of the tapes' usefulness, were obtained. Although no statistical analyses were reported, the subjective measures produced evidence
ALTERING MENTAL STATES 113 supporting the value of the tapes. Motivation was reported as higher and stress as generally lower in the tape group, and the group reported that they perceived the tapes as useful. Comparing the test class with the previous class on performance, however, produced mixed results. A1- though a slightly higher percentage of the test class eventually graduated (50 versus 45.8 percent), more of them required special tutoring than was the case in the control class (66.7 versus 53.7 percent). Thus, the value of the tapes in improving performance was not demonstrated, although some effect in motivation and stress reduction was observed. It is important to note, however, that all participants were fully aware of the purpose of the tapes from the outset, making it possible that expectancy effects or Hawthorne effects were responsible for the results. In addition, in the absence of evidence showing the equivalence of the test group and control group on relevant dimensions, any comparison of the two is open to multiple interpretations, especially in light of the absences and dropouts that occurred in the course of data collection with a small sample. Another study, conducted by a professor of music who is a member of the Monroe Institute, examined the effect of Hemi-Sync~ on the performance of students required to identify melodic and harmonic intervals as part of an ear training course. Forty-five students participated, with assignment to Hemi-Sync~ and control groups done on a random basis. The series of six taped lectures, each with a pretest and posttest, was identical for both groups, except for the presence of Hemi-Sync~ stimuli in the experimental condition. Students were not informed of the nature of the study, nor were personnel involved in distributing the tapes aware of the assignment of individuals to conditions. A 5.5 percent advantage for the experimental group (averaged across sessions) was found, although the difference was not statistically significant. The investigator notes that the Hemi-Sync~ sounds themselves may have interfered with the sounds the students were asked to judge, resulting in lower performance than might otherwise have been expected. The third study involved the random assignment of half of a class of 48 community college students enrolled in introductory psychology to a Hemi-Sync~ condition. All students attended the same lectures and used the same text, but the Hemi-Sync~ students supplemented these with a series of tapes consisting of Hemi-Sync~ sounds mixed with sentences, up to four seconds long, defining terms and key concepts in psychology. On five of six tests, the experimental group performed significantly higher, averaging 10.19 percent better performance. The investigator noted the problem of confounding the effects of Hemi-Sync~ with exposure to material on key concepts and reports that, to control for this, the lecturer presented the same statements through headphones to all students in the classroom. The investigator did not, however, acknowledge the advantage
4 ENHANCING HUMAN PERFORMANCE that the Hemi-Sync<3 group would have as a result of its additional exposure to these concepts on their tapes. Other references are made in the material that was received by the committee to the use of Hemi-Sync~ in educational settings involving the presentation of stimuli through speakers placed on either side of the classroom. No data were provided from studies using this procedure in a formal classroom setting. Although the presentation of Hemi-Sync sounds in free field does not preserve the conditions necessary for binaural beats, the Monroe Institute reports that adequate separation of speakers produces comparable results in terms of frequency following. The review of Hemi-Sync~ in educational settings presented above illustrates the problem with the evidence that has been presented to support it. Most findings are either anecdotal in nature or weak, with multiple potential confoundings such as failure to ensure equivalence of groups or to obtain pretest data, Hawthorne or expectancy effects, and other problems in interpretation. An additional difficulty in evaluating the use of Hemi-Synct3 in educational settings results from its use in conjunction with other procedures and stimuli such as guided imagery and music. For example, a typical Hemi-Sync<3 tape involves the binaural beat stimuli presented at near-threshold levels, embedded in a background of the sounds of ocean surf or music of various types. Hemi-Sync~ as such is rarely studied in isolation; thus its effects, if any, become confounded with the other stimuli and procedures that accompany its presentation. CONCLUSIONS A review of the literature on brain asymmetry reveals a variety of interesting differences in function between the hemispheres. The current state of knowledge suggests, however, that attempts to apply what is known about hemispheric differences to the enhancement of learning and performance are premature. Valid and reliable measures of hemispheric activity in individuals will be necessary before claims linking the performance of an individual to his or her particular pattern of differential hemispheric involvement can be evaluated scientifically. Attempts to increase information-processing capacity by presenting material separately to the two hemispheres do not appear to be useful. Current support for the value of techniques to integrate hemisperic activity to enhance performance (such as Hemi- Sync~) does not meet generally accepted criteria for scientific evidence. Such techniques should be considered further by the Army only if such evidence is provided to and evaluated by the Army Research Institute.