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Sunday, March 06, 2005

Conversation with Dr. Jaak Panksepp on the neural foundations of Incest Aversion

Jaak Panksepp

A response to the article: Incestuous Science: Evolutionary Psychology, Behaviorism, and the Incest Taboo

Panksepp: …Of course, your incest question cannot easily be answered at an empirical level. As you might suspect, my own thinking would tend toward a neuro-ethological emotional systems perspective. All of the ingrained emotional systems of the brain have sensitivities that fluctuate as a function of experience, and the more a system has been repeatedly stimulated naturally by a single type of stimulus, the more it habituates to further arousal. On the surface, I agree this strong psycho-behavioral tendency may be encapsulated in the concept of "blocking" but a deeper understanding would, of course, require consideration of the underlying neural issues. . . which perhaps no one has yet attempted.
Marr: I agree that an answer to the incest question cannot be easily answered from a integrated behavioral (molar or overt behavior) and neuro-psychological (molecular or covert behavior) level, but the point is that an attempt to provide an answer from such a comprehensive empirical perspective has never been made. In my opinion, this is because of a pervasive neglect of neuroscience by social science, and an equally common neglect of applying the metaphors of neuroscience to explain (however imperfectly) key behavioral traits of humankind, of which incest is one example. To wit, there is no literature in learning theory or neuro-psychology that explores the actual neuro-behavioral mechanics of incest aversion, and for the social sciences (sociology, anthropology, social psychology, evolutionary psychology), neuroscience is generally neglected as an informing discipline, and thus explanations for incest are based on simplistic ‘blank slate’ concepts of conditioning, or teleologically inferred instinctive brain states or circuits that have are equally uninformed by neuroscience. So arguments of nature vs. nurture regarding ‘incest’ are inherently unresolvable because neither of them are grounded to our knowledge of our organic brain.
Secondly, as I read the relevant literature, ‘blocking’ and ‘habituation’ are two different things that differ in their behavioral and neural instantiations, and both must be considered as variables that simultaneously come into play to influence sexual aversion, or on the flip side, sexual anticipation. Whereas habituation refers to a diminution of sensitivity to primary unconditioned stimuli (US’s such as food, sex, alcohol), blocking refers to the reduction in the associative strength of redundant discriminative or conditioned stimuli (CS’s such as sounds, visual cues, etc.). There are many neurally based hypotheses for blocking that are being researched empirically and debated in the research literature, but none involve habituation per se.
Panksepp: With respect to incest-avoidance, I have tended to think in terms of opioid modulation of social affect. It is well established that both sexual and non-sexual social pleasures have substantial opioid components, and it is also known that opioid pleasure is self-limiting (i.e., tolerance sets in, which helps to make new patterns of stimulation more attractive/salient)—yielding perhaps, the time tested result that "exotic is erotic." If one assumes that opioids in the brain are state-control rather than information-control systems, and hence have widely broadcast effects in the brain, I could imagine that continuous social exposure will desensitize opioid fields in the brain to sexual arousal by those same stimuli, yielding diminished erotic desires toward those habituated inputs. In other words, one would need new perceptual inputs to arouse sexual appetitive arousal. Very similar processes happen in feeding with stimulus-specific satieties, but they appear to have different time-scales, with dishabituation being perhaps more rapid for gustatory rewards than sexual ones (although I can’t remember anyone ever contrasting them directly).

Of course, there are bound to be many more relevant brain chemistries involved than just endogenous opioids, but I think this type of view could almost be seen as a compromise between the type of behaviorist view you are advancing and a more teleological evolutionary view that is coupled to real neural-systems analysis. I agree that the traditional social-psych evolutionary psychology view is off the mark, but one can imagine a teleology being built into a relevant emotional system at a neurochemically controlled neuro-affective level (e.g., the time-courses of tolerance in different appetitive and reward systems). In this view "blocking" become a multi-dimensional conceptual category that needs to be cashed out in neuroscientific research programs that pay equal respect to traditional learning theory and neuro-ethological approaches that do not neglect basic affective constructs.
Marr: Any rewarding experience, from a day on the beach to a roll in the hay represents a multiple array of stimulus events that may be experienced in full or experienced in some attenuated form. For example, I may daily drive past the beach and daily see an attractive coworker, but experiencing a day at the beach or an affair with that coworker introduces many more stimulus events than can be otherwise anticipated or modeled. So can habituation occur to an entire experience if only the shadow of that experience is perceived? Common experience at least suggests not. That is, attenuated experience (continually seeing a member of the opposite sex) does not habituate the entire experience (continually having sexual relations with a member of the opposite sex). This is not true from practical experience (we can have obsessions for the girl next door that are actually fueled by casual contact) nor would I gather from experimental evidence.
Essentially, incest aversion, or more appropriately, incest apathy represents a decrease in the affective state that is embodied in the anticipation of having sex with kith or kin, and the neurological events that underscore that anticipation (namely the activity of midbrain dopamine systems). Anticipation (or cognitive modeling or fantasy) may be rapidly suppressed by the sudden realization of the strong negative implications of the very act of fantasy (which explains the rapid sexual disinterest that follows when we are for introduced to kin folk such as first cousins, adopted children, in-laws, etc.), and it may be slowly suppressed by ‘blocking’ mechanisms that represent the interference of prior learning with new experiences that logically should elicit sexual response. Of course, anticipation may be indirectly reduced through the habituation of a goal state that habituates with experience, but because we do not truly experience a sexual experience that reduces the salience of a stimulus object (e.g. the girl next door), habituation to my mind is not the primary cause of incest aversion.
Finally, your comment on the necessity to ‘cash out’ blocking concepts through neuroscience is on mark, and current research on blocking integrates neuroscience with learning theory and ethology. However, I believe teleological reasons have little or no bearing on the neurological data that are used in current research on the phenomenon, mainly because teleological reasons are untestable in principle. For example, I see little or no evidence of teleological reasoning common in evolutionary psychology in any of the literature of learning theory (although such reasoning is often used to preface scholarly articles in learning theory) but the primacy of ethological and neurological perspectives is commonly granted.
Pankesepp: It does seem that your approach is respecting such levels, as is Kent Berridge’s adaptation of our own expectancy/SEEKING view, but I don’t see much of such rational blending of ethological and neural analyzes in modern bio-behavioral approaches. For instance, Wolfram Schulz, with his wonderful recordings from primate DA cells, seems to be forcing an associationist type "reward-prediction error" view onto a brain system that is fundamentally a core motivational/emotional state-control system. He is using correlative data about the many converging inputs to the dopamine system to generate a causal argument as to the outputs of the system, while ignoring a mountain of data about the ethological behavior patterns the DA system promotes. That strikes me as a fundamental error (mistaking correlates for causes), but one that seems to be rapidly assimilated by the robust and lively neuro-behaviorist community.
Marr : I agree in principle with your comments, but I think that problems you cite are a matter of neglect rather than representative of a fundamental disagreement (after all, neuroscientists are far more constrained by the empirical facts of behavior, neural or otherwise, than any other group of psychologists I know). Call it if you will a sin of omission rather than commission, a sin that (and I say this with respect) you too may charged with making, since in your book ‘Affective Neuroscience’ learning theory was not emphasized. Let me clarify my position with a more fitting example than Shultz.
Shulz’s ‘prediction error’ conceptualization of reinforcement finds a much more comprehensive representation in the work of the neuropsychologists (and Skinnerian behaviorists) John Donahoe and David Palmer (available in selected pdf re-prints- 1997- on the website of the Journal of the Experimental Analysis of Behavior). In 1993, their book ‘Learning and Complex Behavior’ posited a unified reinforcement principle that closely approximates Shulz’s later work. The URP applied to both respondent (Pavlovian) and operant (Skinnerian) behavior, and reinforcement is grounded to dopamine activity. Thus reinforcement occurs when a ‘discrepancy’ is perceived on a behavioral level, and on a neural level when dopamine is liberated between the synaptic clefts between neurons. As such dopamine contributes to anticipatory processes necessary for preparing voluntary action by focusing attention, increasing synaptic efficiency, and on a conscious level, is reported as an affective state. However, the role of dopamine as a critical constituent of affect, and as one of the biochemical bases of other critical emotional systems (fear, attachment, play) of emotion, is entirely ignored in D and P’s work, and in private correspondence David Palmer admitted as much, claiming that space would not allow a full integration of emotion into their analysis. Neglect of course is not a research strategy, but the continual refusal to comprehensively understand the ramifications of an organic brain is far more of a problem among social scientists in the large such as sociologists, anthropologists, and evolutionary psychologists. I have no easy answer for this problem, save for my own private effort from my own drmezmer website to satirize and expose this shameful state of affairs that has made psychology more of a failed science than a mind science.
Panksepp: I like the way that you emphasize the need to blend ethological and learning-theory perspectives, but I do not see that synthesis emerging robustly in the neuro-behaviorist literature that I read. For instance, the amygdala-fear-learning community almost completely ignores the evolutionarily provided FEAR system of the brain which descends from the amygdala. Hardly a soul on the Anglo-American scene is willing to even entertain that such an evolved emotional system does elaborate some experiential aspects—-rather, envisioning it as a psychologically vacuous motor-output system. From my perspective, the many intrinsic emotional/action tools that evolution provided so that learning mechanisms could work efficiently are still being largely neglected (if not actively marginalized). Am I missing something? Has an explicit consideration of affect and other aspects of consciousness become mainstream in the bio-behavioral approach? Is there a literature that you would recommend getting in touch with? You might also note such a literature, if it exists, in your essay. If that literature really does not exist, what needs to be done to help shake the system toward a coherent psycho-evolutionary-ethological-learning systems synthesis? I think only an even-handed blending of such views could reverse the tide of fairly shallow (i.e., teleologically modularized) evolutionary psychology thinking that has captivated so many brilliant minds.
The literature that you are seeking does not exist, since psychological research is fragmented into separate data languages and methodologies that are rarely seen as interdependent. Consider the ethologically informed mind sciences of learning theory (e.g. Pavlov, Tolman, Bolles, Skinner, etc.) and affective neuroscience (Panksepp, Berridge, Damasio). Ultimately, affective neuroscience is integral to learning theory (and vice versa), but such interdependence requires an integration of disparate sets of metaphors, from the contingency and associational language of behaviorism to the molecular language of neuroscience to the molar language of expectancy, emotion, and affect. Such a pluralistic yet neurologically grounded point of view is not within the purview of journalistic literature, which as a matter of course is far more restrictive in the data languages and methodologies that are permitted. But it is within the domain of explanatory models that are more literary in scope and can be constructed with both academic and popular audiences in mind. To my knowledge only the neuro-psychologist Kent Berridge has attempted to merge learning theory and affective neuroscience in his admirable synthesizing perspectives, yet his work is not well known and its practical and philosophical implications unplumbed. The only ‘popular’ literature that advances such an explanatory frame work is provided from of all places, linguistics. Cognitive linguistics (the work of Lakoff, Falconnier, Turner, etc.) demonstrates that language and comprehension is rooted not in a disembodied logic, but from embodied processes that are not digital, but are emerge from an organic brain.
My derivation of an explanation of incest avoidance from learning theory (blocking) and affective neuroscience is a case in point. Incest aversion is a topic of interest primarily to evolutionary psychology, sociology and anthropology, whereas blocking derives from learning theory and neuromodulator (dopamine) based accounts of incentive motivation come from neuroscience. Where does one begin to find an academic audience that knows all these disparate subject matters and cares to explore the new directions they may lead both philosophically and psychologically? At present, like Diogenes, I am continuing to look for an honest answer to that question.