Showing papers in "Behavioral and Brain Sciences in 1983"

Intentional systems in cognitive ethology: The 'panglossian paradigm' defended

Abstract: Ethologists and others studying animal behavior in a “cognitive” spirit are in need of a descriptive language and method that are neither anachronistically bound by behaviorist scruples nor prematurely committed to particular “information-processing models.” Just such an interim descriptive method can be found in intentional system theory. The use of intentional system theory is illustrated with the case of the apparently communicative behavior of vervet monkeys. A way of using the theory to generate data - including usable, testable “anecdotal” data - is sketched. The underlying assumptions of this approach can be seen to ally it directly with “adaptationist” theorizing in evolutionary biology, which has recently come under attack from Stephen Gould and Richard Lewontin, who castigate it as the “Panglossian paradigm.” Their arguments, which are strongly analogous to B. F, Skinner's arguments against “mentalism,” point to certain pitfalls that attend the careless exercise of such “Panglossian” thinking (and rival varieties of thinking as well), but do not constitute a fundamental objection to either adaptationist theorizing or its cousin, intentional system theory.

Brain organization for language from the perspective of electrical stimulation mapping

Abstract: A model for the organization of language in the adult humans brain is derived from electrical stimulation mapping of several language-related functions: naming, reading, short-term verbal memory, mimicry of orofacial movements, and phoneme identification during neurosurgical operations under local anesthesia. A common peri-Sylvian cortex for motor and language functions is identified in the language dominant hemisphere, including sites common to sequencing of movements and identification of phonemes that may represent an anatomic substrate for the “motor theory of speech perception.” This is surrounded by sites related to short-term verbal memory, with sites specialized for such language functions as naming or syntax at the interface between these motor and memory areas. Language functions are discretely and differentially localized in association cortex, including some differential localization of the same function, naming, in multiple languages. There is substantial individual variability in the exact location of sites related to a particular function, a variability which can be partly related to the patient's sex and overall language ability and which may depend on prior brain injury and, perhaps subtly, on prior experience. A common “specific alerting response” mechanism for motor and language functions is identified in the lateral thalamus of the language–dominant hemisphere, a mechanism that may select the cortical areas appropriate for a particular language function.

The codes of man and beasts.

Abstract: Abstract Exposing the chimpanzee to language training appears to enhance the animal's ability to perform some kinds of tasks but not others. The abilities that are enhanced involve abstract judgment, as in analogical reasoning, matching proportions of physically unlike exemplars, and completing incomplete (external) representations of action. The abilities that do not improve concern the location of items in space and the inferences one might make in attempting to obtain them. Representing items in space and making inferences about them could be done with an imaginal code, but representing relations and judging the relations between them, as in analogies, requires a more abstract code. Language training cannot instill such an abstract code, but for species that have the code to start with, it may enhance the animal's ability to use it.

Is blindsight an effect of scattered light, spared cortex, and near-threshold vision?

Abstract: Blindsight is the term commonly used to describe visually guided behaviour elicited by a stimulus falling within the scotoma (blind area) caused by a lesion of the striate cortex. Such “vision” is normally held to be unconscious and to be mediated by subcortical pathways involving the superior colliculus. Blindsight is of considerable theoretical importance since it suggests that destriate man is more like destriate monkey than had been previously believed and also because it supports the classical notion of two visual systems. It is also of potential clinical importance, since it has been claimed recently that systematic practice in blindsight can lead to the recovery of normal visual function in patients with cortical lesions. From a review of the literature it is concluded that all of the phenomena of blindsight can be attributed either to light scatter into unimpaired parts of the visual field or to residual vision resulting from spared striate cortex. The possible contribution f other factors is also considered. It is concluded that blindsight studies have generally failed to control for such nonblindsight interpretations partly because of poor methodology and partly because of difficulties in defining the term “blindsight.” Experiments were carried out to investigate the extent to which subjects can exhibit performance similar to blindsight when they are using scattered light as a cue. This was done both with hemianopic subjects (by manipulating the amount of scattered and direct light coming from a stimulus) and with normal subjects (by presenting targets within their blind spots). Good blindsight performance was observed when only scattered light was available as a cue to the subjects. It is therefore concluded that an adequate case for blindsight has not been made. It is probably impossible to demonstrate the existence of blindsight on purely behavioural grounds. What is required is the establishment of relationships between visual function and independent anatomical evidence.

The impending demise of the icon: A critique of the concept of iconic storage in visual information processing

Abstract: Without disputing the experimental evidence that subjects have available most of the content of brief displays for a fraction of a second, or that visual stimuli Persist after their physical termination for a similar time, I argue that this evidence is irrelevant to perception. Specifically, the notion of an icon as a brief storage of information persisting after stimulus termination cannot possibly be useful in any typical visual information-processing task except reading in a lightning storm. Since the visual world that provides the stimuli for perception is continuous and not chopped up by tachistoscopes, and since our eyes and heads are rarely motionless, no realistic circumstances exist in which having a frozen iconic storage of information could be helpful. Rather, the presence of such an icon interferes with perception. This paper examines instances of normal perception, and then reviews experimental evidence on temporal integration, saccadic suppression, masking, and the photoreceptor basis of visual persistence, to further demonstrate that a storage of excitation cannot be a useful device for storing information. Finally, I note that little would have to be changed in our theories of visual perception or information processing if we simply forgot all about the icon and iconic memory as an early stage of processing.

Observing and conditioned reinforcement

Abstract: When experimenters require their subjects to perform some readily recorded response to gain access to discriminative stimuli but do not permit this behavior to alter the schedule of reinforcement, the response is classified, by analogy, as an “observing” response Observing responses have been used not only to analyze discrimination learning but also to substantiate the concept of conditioned reinforcement and to measure the reinforcing effect of stimuli serving other behavioral functions A controversy, however, centers around the puzzling question of how observing can be sustained when the resulting stimuli are not associated with any increase in the frequency of primary reinforcement Two possible answers have been advanced: (a) that differential preparatory responses to these stimuli as conditional stimuli make both the receipt and the nonreceipt of unconditional stimuli more reinforcing; and (b) that information concerning biologically significant events is inherently reinforcing It appears, however, that the stimulus associated with the less desirable outcome is not reinforcing The maintenance of observing can be reconciled with the traditional theory that the acquisition of reinforcing properties proceeds according to the same rules as those for Pavlovian conditioning if it is recognized that the subject is selective in what it observes and procures a greater than proportionate exposure to the stimulus associated with the more desirable outcome As a result of this selection, the overall frequency of primary reinforcement increases in the presence of the observed stimuli and declines in the presence of the nondifferential stimuli that prevail when the subject is not observing

An analysis of psychotherapy versus placebo studies

Abstract: Smith, Glass, and Miller (1980) have reported a meta-analysis of over 500 studies comparing some form of psychological therapy with a control condition. They report that when averaged over all dependent measures of outcome, psychological therapy is. 85 standard deviations better than the control treatment. We examined the subset of studies included in the Smith et al. metaanalysis that contained a psychotherapy and a placebo treatment. The median of the mean effect sizes for these 32 studies was. 15. There was a nonsignificant inverse relationship between mean outcome and the following: sample size, duration of therapy, use of measures of outcome other than undisguised self-report, measurement of outcome at follow-up, and use of real patients rather than subjects solicited for the purposes of participation in a research study. A qualitative analysis of the studies in terms of the type of patient involved indicates that those using psychiatric outpatients had essentially zero effect sizes and that none using psychiatric inpaticnts provide convincing evidence for psychotherapeutic effectiveness. The onty studies clearly demonstrating significant effects of psychotherapy were the ones that did not use real patients. For the most part, these studies involved small samples of subjects and brief treatments, occasionally described in quasibeliavioristic language. It was concluded that for real patients there is no evidence that the benefits of psychotherapy are greater than those of placebo treatment.

Human inbreeding avoidance: Culture in nature

Abstract: Much clinical and ethnographic evidence suggests that humans, like many other organisms, are selected to avoid close inbreeding because of the fitness costs of inbreeding depression. The proximate mechanism of human inbreeding avoidance seems to be precultural, and to involve the interaction of genetic predispositions and environmental conditions. As first suggested by E. Westermarck, and supported by evidence from Israeli kibbutzim, Chinese sim-pua marriage, and much convergent ethnographic and clinical evidence, humans negatively imprint on intimate associates during a critical period of early childhood (between ages 2 and 6).There is also much evidence that, like other social animals, humans do not seek to maximize outbreeding, but rather to maintain an optimal balance between outbreeding and inbreeding. Close inbreeding reduces fitness through inbreeding depression, but some inbreeding brings the benefits of nepotism. For simple, stateless, horticultural societies, the optimal balance seems to be achieved by a combination of precultural inbreeding avoidance of relatives with an r ≤·25 and cultural rules of preferential marriage with kin with r ≥·25. Adjustment of the coefficient of inbreeding to other ecological settings seems to be largely cultural. An interactive model of “culture in nature” is presented, in which culture is seen as coevolving with genes to produce the maxiniization of individual inclusive fitness.

The quantized geometry of visual space: The coherent computation of depth, form, and lightness

Abstract: A theory is presented of how global visual interactions between depth, length, lightness, and form percepts can occur. The theory suggests how quantized activity patterns which reflect these visual properties can coherently fill-in, or complete, visually ambiguous regions starting with visually informative data features. Phenomena such as the Cornsweet and Craik-O'Brien effects, phantoms and subjective contours, binocular brightness summation, the equidistance tendency, Emmert's law, allelotropia, multiple spatial frequency scaling and edge detection, figure-ground completion, coexistence of depth and binocular rivalry, reflectance rivalry, Fechner's paradox, decrease of threshold contrast with increased number of cycles in a grating pattern, hysteresis, adaptation level tuning, Weber law modulation, shift of sensitivity with background luminance, and the finite capacity of visual short term memory are discussed in terms of a small set of concepts and mechanisms. Limitations of alternative visual theories which depend upon Fourier analysis, Laplacians, zero-crossings, and cooperative depth planes are described. Relationships between monocular and binocular processing of the same visual patterns are noted, and a shift in emphasis from edge and disparity computations toward the characterization of resonant activity-scaling correlations across multiple spatial scales is recommended. This recommendation follows from the theory's distinction between the concept of a structural spatial scale, which is determined by local receptive field properties, and a functional spatial scale, which is defined by the interaction between global properties of a visual scene and the network as a whole. Functional spatial scales, but not structural spatial scales, embody the quantization of network activity that reflects a scene's global visual representation. A functional scale is generated by a filling-in resonant exchange, or FIRE, which can be ignited by an exchange of feedback signals among the binocular cells where monocular patterns are binocularly matched.

Precis of knowledge and the flow of information

Abstract: A theory of information is developed in which the informational content of a signal (structure, event) can be specified. This content is expressed by a sentence describing the condition at a source on which the properties of a signal depend in some lawful way. Information, as so defined, though perfectly objective, has the kind of semantic property (intentionality) that seems to be needed for an analysis of cognition. Perceptual knowledge is an information-dependent internal state with a content corresponding to the information producing it. This picture of knowledge captures most of what makes knowledge an important cpistcmological notion. It also avoids many of the problems infecting traditional justificational accounts of knowledge (knowledge as [justified, true belief’). Our information pickup systems are characterized in terms of the way they encode incoming information (perception) for further cognitive processing. Our perceptual experience is distinguished from our perceptual beliefs by the different way sensory information is encoded in these internal structures. Our ropositional attitudes – those (unlike knowledge) having a content that can be either true or false (e.g., belief) – are described in terms of the way internal (presumably neural) structures acquire during learning a certain information-carrying role. The content of these structures (whether true or false) is identified with the kind of information they were developed to carry

Inductive reasoning: Competence or skill?

Abstract: alleged fallacy is in interpreting experiments according to what is advocated by Western moral experts. However, we believe that this argument in fact also provides good grounds for the case of minority intuitions. It has long been maintained that affect and cognition play complementary rather than opposite roles in higher-order psychological processes (Hilgard 1980). The moral expert who views justice in terms of fairness and rationality advocates generalizable decisions made by assuming the role of disadvantaged persons (Kohlberg 1973). To do this effectively requires both cognitive and affective skills. Again, base rate information may be less relevant to expert intuitions than the possession of a rich and varied sociocultural experience, possibly one that draws from extensive anthropological work (Shweder, Turiel & Much 1981). On the one hand, it may be that because of ignorance or lack of education, persons in some cultures would appear less able to take the role of the other in making moral judgments. On the other hand, given the difficulty of designing culture-free tests of moral development (Siegal 1982), it may be that all cultures are equally ignorant or defective in education and that empirical measures are not sensitive enough to give clear indications of the cognitive and affective elements in moral behaviour. However, in either case, irrationality cannot be experimentally demonstrated, and we need the minority intuitions of skilled moral experts to make progress in designing and interpreting experiments on these normative questions.

Problems with current catecholamine hypotheses of antidepressant agents: Speculations leading to a new hypothesis

Abstract: Abstract Problems with current hypotheses of catecholamine involvement in antidepressant action are reviewed. The theories examined include those that attribute a key role to increased brain norepinephrine (NE) availability or to the desensitization of brain beta adrenergic receptors. Although these hypotheses are consistent with a great deal of relevant laboratory and clinical data there arc an increasing number of findings that cannot be explained by them. These contradictions include findings on the lag time between pharmacological and therapeutic effects of antidepressants, the actions of propranolol and thyroid hormones on depression, the relationship between cortisol secretion and depression, the net effect of chronic antidepressants on noradrenergic neurotransmission, and the functions of cyclic AMP in the CNS. To reconcile the discordant data in these areas of research, a new formulation, the output hypothesis, which is derived from the foregoing theories, is proposed. The new hypothesis assumes that depression or adverse behavioral effects of stress results when the output of brain cells bearing noradrenergic receptors is too low to meet increased demand resulting from stress or other biologically disruptive events. According to this view antidepressants act by a mechanism akin to adaptation to chronic stress in which there is a prolonged increase in postsynaptic noradrenergic receptor activation in the brain. The prolonged increase is necessary for NE to induce, via the beta adrenoceptor–cAMP system, trophic or long-term metabolic effects that increase the output of catecholamine effector cells to a level commensurate with demand.

How are grammers represented

Abstract: Noam Chomsky and other linguists and psychologists have suggested that human linguistic behavior is somehow governed by a mental representation of a transformational grammar. Challenges to this controversial claim have often been met by invoking an explicitly computational perspective: It makes perfect sense to suppose that a grammar could be represented in the memory of a computational device and that this grammar could govern the device's use of a language. This paper urges, however, that the claim that humans are such a device is unsupported and that it seems unlikely that linguists and psychologists really want to claim any such thing. Evidence for the linguists' original claim is drawn from three main sources: the explanation of language comprehension and other linguistic abilities; evidence for formal properties of the rules of the grammar; and the explanation of language acquisition. It is argued in this paper that none of these sources provides support for the view that the grammar governs language processing in something like the way a program governs the operation of a programmed machine. The computational approach, on the contrary, suggests ways in which linguistic abilities can be explained without the attribution of any explicit representation of rules governing linguistic behavior.

Story grammars versus story points

Abstract: Story grammars have been proposed as a means of expressing a theory of stories. Story grammarians claim that stories are a linguistic form in much the same sense that sentences are, and that we can attribute constituent structure to stories in much the same way we attribute it to sentences. Just as sentences and their constituent structure can be characterized by sentence grammars, so stories and their constituent structure can be characterized by a story grammar. However, the analogy between story grammars and sentence grammars is ill conceived. It is based on a category error that assumes stories to be textual entities like sentences. This is demonstrably not the case. Moreover, this confusion is the cause of most of the misunderstandings about story grammars and what they can accomplish. Once this mistake is acknowledged, the possible contribution of story grammars to a theory of stories is considerably diminished. In place of story grammars, I propose the rudiments of a theory, called the theory of story points. Although it lacks some of the aesthetic appeal of story grammars, the theory of story points seems a more promising route to a meaningful theory of stories. The theory is being used as a component of a computer story-understanding system under development at Berkeley. In addition, some very preliminary experiments conducted on the basis of this approach seem to lend it some psychological plausibility.

Who commits the base rate fallacy

Abstract: processes. On our reading, this is the force of much of the recent work on reasoning. Cohen's claim that a theory of competence is all one needs for a theory of reasoning may also rest on an ill-conceived analogy: that theories of competence are to psychology what idealized models are to the natural sciences. Though widely drawn, this parallel is inaccurate. Idealizations in the natural sciences for example, the ideal gas laws or the Hardy-Weinberg law of equilibrium may describe the behavior of entities or systems under ideal conditions. Nevertheless, they are not used to do so. Idealized laws, rather, provide a way to describe an ideal state so that departures from the ideal may be explained in terms of factors predictable by parameters of the model. To date, psychologists have been unable to find idealized models that may be treated in this way with any success. Chomsky's theory of competence, for instance, though somewhat descriptive of speech produced under ideal circumstances, never provided a model in which everyday linguistic behavior could be explained. Similarly, competence models of reasoning will carry no weight as scientific idealizations unless formulated in such a way that departures from idealized behavior can be explained in terms of the idealized mechanisms.

The controversy about irrationality

Abstract: of the original article: The traditional verbal/nonverbal dichotomy is inadequate for completely describing cerebral lateralization. Musical functions are not necessarily mediated by the right hemisphere; evidence for a specialist left-hemisphere mechanism dedicated to the encoded speech signal is weakening, and the right hemisphere possesses considerable comprehensional powers. Right-hemisphere processing is often said to be characterized by holistic or gestalt apprehension, and face recognition may be mediated by this hemisphere partly because of these powers, partly because of the right hemisphere's involvement in emotional affect, and possibly through the hypothesized existence of a specialist face processor or processors in the right. The latter hypothesis may, however, suffer the same fate as the one relating to a specialist encodedness processor for speech in the left. Verbal processing is largely the province of the left because of this hemisphere's possession of sequential, analytic, timedependent mechanisms. Other distinctions (e.g., focal/diffuse and serial/parallel) are special cases of an analytic/holistic dichotomy. More fundamentally, however, the left hemisphere is characterized by its mediation of discriminations involving duration, temporal order, sequencing, and rhythm, at the sensory (tactual, visual, and, above all, auditory) level, and especially at the motor level (for fingers, limbs, and, above all, the speech apparatus). Spatial aspects characterize the right, the mapping of exteroceptive body space, and the positions of fingers, limbs, and perhaps articulators, with respect to actual and target positions. Thus there is a continuum of function between the hemispheres, rather than a rigid dichotomy, the differences being quantitative rather than qualitative, of degree rather than of kind. Hemispheric specialization and cerebral duality J. E. Bogen and G. M. Bogen New Hope Pain Center, Alhambra, Calif. 91801 Bradshaw & Nettleton (B & N) (1981b) presented a thoughtful and detailed, almost heroic, review of recent studies on hemispheric specialization (HS). They have, perforce, omitted a historical perspective, some of which we should like to supply in this commentary. Following a capsulization of the neurologic background, we discuss the reasonableness of condensing the facts of HS into one or another dichotomous comparison, and then conclude with some comments on the concept of hemisphericity. A. Neurologic origins. The fact of hemispheric dominance in THE BEHAVIORAL AND BRAIN SCIENCES (1983) 3 517

Can irrationality be intelligently discussed

Abstract: that can be pressed into service for many tasks, sometimes appropriately, sometimes not. So Cohen attacks heuristics. But is this attack necessary, even from Cohen's own point of view? Why not simply regard the heuristics as tools or subroutines available to more specific mechanisms? I wish to comment also on Cohen's discussion of Bayes' theorem. As I see it, the fundamental difficulty with the Bayesian analyses Cohen criticizes is that they do not allow for an assessment of the reliability and relevance of \"base rates. ' We are not certain that the predominance of blue cabs in the city as a whole is fully relevant to the particular situation. In a recent paper (Shafer 1982) I discuss how base rates can be discounted using the theory of belief functions; it turns out that one obtains the Bayesian answer if the discount rate is sufficiently low, but that even a moderate discount rate can sharply reduce the influence of the base rate in the face of conflicting evidence. Cohen seems to feel that base rates should always be totally discounted, and this is very difficult to sustain. In Cohens medical story, for example, the Bayesian analysis seems compelling if there is no reason to discount the relative rarity of disease B.

The two visual system hypothesis loses a supporter

Abstract: ago, it is almost certainly a constant and useful capacity of the' human (or nonhuman, for that matter) organism. I further object vigorously to Campion et al.'s (probably careless) remark that consciousness \"cannot be investigated scientifically.\" What in the world cannot be investigated scientifically? Only something supernatural, by definition. I trust it was only laziness or contempt for philosophy that led them to take such a heavy philosophical position against the very conception of the world that legitimates scientific investigation.

Physical correlate theory versus the indirect calibration approach

Abstract: of the original article: The measurement of sensory intensity has had a long history, attracting the attention of investigators from many disciplines including physiology, psychology, physics, mathematics, philosophy, and even chemistry. While there has been a continuing doubt by some that sensation has the properties necessary for measurement, experiments designed to obtain estimates of sensory intensity have found that a general rule applies: Equal stimulus ratios produce equal sensory ratios. Theories concerning the basis for this simple psychophysical rule are discussed, with emphasis given to the physical correlate theory, which considers judgments of subjective magnitudes to be based upon estimates of physical dimensions that vary regularly with changes in degree of stimulation. For the most thoroughly investigated sensory scales, brightness and loudness, the physical correlate is considered to be distance. Our "tacit knowledge" of the sensory effects of changing distance plays an essential role in matching motor activities to environmental conditions and in ensuring accurate perceptual evaluations through brightness and loudness constancies. In psychophysical experiments, subjects apparently use this same tacit knowledge when required to estimate relative subjective magnitudes. The evidence related to the physical correlate theory is summarized, and it is concluded that, while under appropriate conditions we demonstrate considerable skill in evaluating environmental relationships, we are quite unable to estimate the neurophysiological nature or quantity of sensory response. A psychophysics devoted to studying conditions required for accuracy and conditions producing errors in the perception of environmental relationships would seem to be more valuable than one devoted to subjective magnitudes. Physical correlate theory versus the indirect calibration approach

Two hemispheres but one brain

Abstract: of the original article: A review of research with chicks, songbirds, rodents, and nonhuman primates indicates that the brain is lateralized for a number of behavioral functions. These findings can be understood in terms of three hypothetical brain processes derived from a brain model based on general systems theory: hemispheric activation, interhemispheric inhibition, and intcrhemisphcric coupling. Left-hemisphere activation occurs in songbirds and nonhuman primates in response to salient auditory or visual input, or when a communicative output is required. The right hemisphere is activated in rats when spatial performance is required, and in chicks when they are placed in an emotion-provoking situation. In rats and chicks interhemispheric activation and inhibition occur when there is an affective component in the environment (novelty, aversive conditioning) or when an emotional response is emitted (copulation, attack, killing). An interhemispheric coupling (correlation) found in rats and rabbits implies that the hemispheres are two major components in a control system with a negative feedback loop. Early-experience variables in rats can induce laterality in a symmetric brain or facilitate its development in an already biased brain. It is predicted that functional lateralization, when present, will be similar across species: the left hemisphere will tend to be involved in communicative functions while the right hemisphere will respond to spatial and affective information; both hemispheres will often interact via activation-inhibition mechanisms when affective or emotional processes are involved. Homologous brain areas and their connecting callosal fibers must be intact at birth and must remain intact throughout development for lateralization to reach its maximum level. Injury to any portion of this unit will result in hemispheric redundancy rather than specialization. One major function of early experience is to provide stimulation during development, which acts to enhance the growth and development of the corpus callosum, thereby giving rise to a more specialized brain. Two hemispheres but one brain G. Berlucchi Islituto di Fisiologia dell University di Pisa e Istituto di Neurofisiologia del CNR, Pisa, Italy Dencnberg's (1981a) theory about hemisphereic interaction suffers from a general lack of clear anatomical and physiological definitions. For example, the term \"hemisphere\" is loosely used as synonymous with \"cortex,\" while according to the standard anatomical nomenclature the basal ganglia, the hippocampal formation, and the amygdaloid complex are also parts of each cerebral hemisphere of the mammalian brain. Expressions such as \"hemispheric activation\" and \"interhemispheric inhibition\" have little use unless one refers to specific anatomical entities and physiological processes. There are several recent studies on regional blood flow in the intact human brain to show that if \"hemispheric activation\" means increase in neuronal activity in certain or all parts of one hemisphere, with no change, or even a decrease, in neuronal activity in the other hemisphere, then it is indeed a rare occurrence, if it exists at all. Even during the execution of mental or behavioral tasks that are supposed to be strongly lateralized, changes in regional blood flow in corresponding areas of the two sides, which are strictly parallel to changes in neuronal activity, tend to be roughly equal (see, e.g., Larsen, Skinh0j & Lassen 1975; Prohovnik, Hakansson & Risberg 1980; Risbcrg, Halsey, Wills & Wilson 1975; Roland, Larsen, Lassen & Skinh0j 1980; Roland, Skinh0j, Lassen & Larsen 1980). If by \"interhemispheric inhibition\" one means that neuronal activity in one hemisphere reduces or suppresses activity in the other hemisphere, then the evidence that this takes place in the intact brain is again, at best, meager. Prohovnik et al. (1980) have noticed a conspicuous lack of negative correlations between the activities of homologous regions of the conscious human brain. Whether cross-inhibition occurs at subcortical levels is another problem. Risberg ctal. (1975), after testing the effects of a verbal task and a spatial task on regional cerebral blood flow (rCBF) in normal humans, concluded that \"rCBF increases during 'unilateral' activation take place in both hemispheres, indicating the importance of integration of brain activity mediated by the cerebral commissures, especially the corpus callosum.\" This brings me to Denenberg's general misrepresentation of commissurai functions. In principle, his theory does not require major participation of the cerebral commissures in the putative mechanisms of interhemispheric inhibition and in the control of the negative feedback loop between the coupled hemispheres since the outputs.of the two hemispheres might compete at the motoneuronal level. Yet Denenberg makes it clear that he believes that the corpus callosum is the most likely candidate for fulfilling these functions, although he gives little evidence in support of his belief. He certainly cannot use as evidence for callosal inhibition the finding of Glick (1975) that a section of the anterior corpus callosum in rats increased the number of rotations induced by amphetamine administration. According to the authors this phenomenon results from the interruption of a pathway between the right and left caudate nuclei that passes through the ventral corpus callosum, resulting in the accentuation or the establishment of neurochemical striatal asymmetries. Their suggestion is that this pathway serves to synchronize the activities of the two corpora striata, rather than, as Denenberg instead suggests, to mediate cross-inhibition between higher cortical centers. I am amazed by the complete lack of consideration on Denenberg's part of the enormous literature on unilateral cortical spreading depression (see e.g. BureS, BureSovd & Kfivdnek 1974; and the commentary of BureS, BureJovii & Kfivdnek 1981), which, in my view, gives very little support for the hypothesis of hemispheric dominance and interhemispheric inhibition on rats. To the extent that Denenberg's model is a neurodynamic one (i.e., to the extent that his putative mechanisms of hemispheric interaction are physiological influences rather than long-term biochemical changes), reversible inactivation of one hemisphere by spreading depression would provide an excellent means to test his ideas directly. THE. BEHAVIORAL AND BRAIN SCIENCES (1983) 1 171 Continuing Commentary To return to the physiology of the cortical commissures, I have recently reviewed a massive body of evidence indicating that the functional significance of these connections lies in the unification of sensory information coming from the two halves of the body or the visual field and, in general, the equalization of activity in corresponding regions of the two hemispheres (Berlucchi 1981a). This is fully in accord with Sperry's idea that the corpus callusom has a unifying role in conscious experience and cortical activity (Sperry 1974). As an example, visual receptive fields of neurons in the inferotemporal cortex of the monkey extend across the vertical midline of the visual field and have the same response properties throughout (see Gross, Bender & Mishkin 1979). Since the input to these neurons from the contralateral visual field is conveyed by thalamocortical projections or intrahemispheric corticocortical projections, and the input from the ipsilateral visual field is conveyed by the corpus callosum or anterior commissure, such continuous and homogeneous receptive fields provide a good indication of the integration between intrahemispheric and interhemispheric inputs, and no evidence for interhemispheric inhibition. I fail to see the analogy between the competition between the inputs from the two eyes in the lateral developing geniculate nucleus and the proposed action or inaction of the corpus callosum in development and maturation, as suggested by Denenberg (1981a on pp. 52 ff.). Whatever evidence is available on the development of callosal fibers indicates the callosal connections are modified according to the functional needs of their target areas, and exert no definite influence on the organization and connectivity of such areas during development and maturation. Thus, callosal connections uniting cortical points representing eccentric portions of the visual field are dropped in the postnatal period in the cat (see Innocenti 1980), probably because it would be meaningless to receive incongruent visual information from the far right and left fields at the same cortical point (see Berlucchi 1981a). The general rule appears to be that callosal and noncallosal inputs to the same cortical area are blended and integrated into a functional whole, and where there seems to be a segregation of callosal and noncallosal inputs, as in the somatic sensory cortex of the rat, there is no competition between the two sets of inputs during development (see Wise & Jones 1978). I like Denenberg's suggestion that homologous regions of the two hemispheres make up a functional unit because of their commissural connections, but my view of such a functional unit is very different from his (Berlucchi 1981b). I believe that corresponding cytoarchitectural areas of the two sides have exactly the same physiological organization and general function in behavior, and the commissural links serve to ensure a yoked synchronous and congruent activity in the two members of each pair of areas. Hemispheric asymmetry arises when the two areas constituting a bilateral functional unit are asymmetrical (a good example is the temporoparietal transitional area in the human brain; see Galaburda, Sanides & Geschwind 1978), so that the area on one side is larger or has a higher neuronal density than that on the other. Under these conditions, I submit, the callosal connections of such areas would also be asymmetrical, the projections arising from the larger area b

Science as an international system

Abstract: reasons, acquires his spoken language, and so on. Notice that if animals are ascribed beliefs and desires, then on this conception of representations, they too have an innate and inner language, and their reasoning consists in an inner manipulation of linguistic symbols. Accordingly, if the vervet and I both believe there is a leopard nearby, we both stand in a particular relation to the same inner linguistic structure, one analogous to the English sentence \"there is a leopard nearby.\" I find this view of representations excessively narrow and impossible to accept, for humans or for other animals (see P. S. Churchland 1980a; 1980b; see also Stich 1982). While there are a host of serious objections, the point of emphasis here is that human language has the earmarks of a device for communication, and as such, it is probably a latecomer in the representational business of organisms. Evolutionary and neurobiological considerations cry out against the likelihood that all representations in the brains are to be modeled on linguistic representations; rather, the deeper understanding of linguistic representation may come from a theory of more primitive kinds of representations. The implication that vervet or rattlesnake brains manipulate sentences, noun phrases, verb phrases, and the rest, is grimly far-fetched, though representations they surely do enjoy (see P. S. Churchland & P. M. Churchland 1983). In short, the best cognitively based theory of representations looks profoundly troubled. How does Dennett cope with this problem? First, he agrees that the sentences-in-the-head theory of beliefs is a flop; indeed, he has argued this most convincingly himself (Dennett 1978a). Second, he nonetheless sees no problem in ascribing beliefs to humans and to vervets. But then what structures does Dennett think are in the head such that the vervet and I both believe there is a leopard nearby? His answer: none. Beliefs, it appears, are not (for the most part?) in the head; they are \"virtual\" (Dennett 1981b, pp. 48-49), and the actual, causally relevant states in the production of behavior are not beliefs and desires at all. This should be deeply troubling, for if beliefs and desires are not really in the brain, then it becomes questionable whether any explanatory work is done by attributing beliefs and desires to organisms. It appears that Dennett, faced with the catastrophe devolving from the sentences-in-the-head theory of cognitive representations, has engaged in special pleading for beliefdesire psychology: he claims that belief-desire theory cannot be falsified, and that it is merely a way of organizing data, as opposed, presumably, to postulating causally active inner states of the organism. The crux of the matter is that Dennett gives belief-desire psychology an instntmentalistic interpretation, and beliefs and desires are therefore no longer construed as real states of the brain, but as virtual states. He argues that belief-desire \"theory\" is not a theory in the \"classical\" mode; but then, alas, it certainly does not permit explanations in any recognizable mode either, for, as an instrument, it does not explain at all. As a convenient fiction, it may help to predict, but as a fiction, it cannot pretend to any explanatory function. One can decide to be an instrumentalist about any theory: vitalism, alchemy, Aristotelian biology, and so on. Just claim that the theory does not aspire to truth, but is a convenient fiction, and so cannot be falsified either. But there is no acceptable way to be an instrumentalist while playing the explanatory game. Part of the price you pay for saving a theory from revision by giving it instrumentalistic shelter and \"protected status\" is that the theory is thereby put beyond the bounds of testability, falsifiability, reducibility, coherence with related theories, and general scientific status. That appears not to bother Dennett at all, but once pointed out, it may reduce any cthologist's enthusiasm for Dennett's approach. Of course, there is not yet a theory available with which to replace beliefdesire psychology, so we muck on nonetheless. Nor do I object to using a flawed theory to make do, especially if it can be the means of bootstrapping up to an entirely new theory, so long as the absence of a replacing theory is not used to sanctify the doddering theory. But by propping up belief-desire psychology with an instrumentalist stick, one fosters the illusion that it can stand on its own feet like any scientific theory, with the result that the impetus to improve upon it, revise it, and look for alternative theories, is diminished. Having thus scowled and scoffed, I should nevertheless like to applaud Dennett's underlying conviction that human and nonhuman behavior alike ought to be encompassed by a single theory. Otherwise put, if belief-desire psychology is an adequate theory for human behavior, then it should be adequate to lots of nonhuman behavior. My point is that belief-desire psychology is fraught with troubles, and ethologists should be warned that if they buy into it, they buy into its troubles as well (P. M. Churchland 1981).