The Seven Sins of Evolutionary Psychology - Konrad Lorenz Institute

Gerhard Meisenbergstraight into the buffers of working memory to produceconscious feelings. If all this seems too messyto be true, ask a neuroanatomist to describe the fiberconnections in this brain region (PRICE/CARMICHAEL/DREVETS 1996)! Of course, the extent to which orbitofrontalfunctions are truly modular or merelymodularized, and how modularization is achieved,are wide open questions.And what about the subcortical systems that P&Pchampion as the closest approximation to sociobiologicalmodules? My first objection to their descriptionis that it exaggerates the achievements of subcorticalneuroscience. True, there is an abundantliterature about the brain systems that underlie autonomicregulation, arousal, and even some specificemotional responses, but we still don’t know how itall fits together. For example, electrical self-stimulationof subcortical brain sites has been studied in ratsfor nearly half a century, since 1953. And yet, we stillhave no good description of the underlying circuitry.We don’t even know whether self-stimulation sitesin places such as the midbrain, lateral hypothalamusand septal area belong to the same reinforcementcircuitry or whether they represent functionally independentsystems. We don’t even know the exactrole of the mesolimbic dopamine system in this circuitryalthough we have drugs such as amphetaminethat can produce euphoria by stimulating this system(KALIVAS/NAKAMURA 1999; ROBBINS/EVERITT1996; SPANAGEL/WEISS 1999).There can be no reasonable doubt that the subcorticalsystems mentioned by P&P are hard-wired. Andstill, some of them are not good examples for ‘sociobiological’modules because they did not evolve intheir present form in response to a specifiable adaptivechallenge. Thus, the cells of the mesolimbicdopamine system become active when the animaleither experiences or expects reward, and they reducetheir activity when the expectation of rewardis frustrated (SCHULTZ 1998). Together with the observationthat psychostimulant drugs activate thissystem, this points to a specific involvement in positivereinforcement and possibly even the consciousexperience of pleasure. However, the same neuronsare also activated during stress, for example when arat expects a painful electrical shock or is immobilizedon the laboratory bench with duct tape (D’AN-GIO/SERRATO/SCATTON 1990; IMPERATO et al. 1992).Unless laboratory rats are masochists, the dopaminecells are unlikely to function as mediators of pleasureor positive reinforcement in these situations. We canstill save the function-specific model by claimingthat mesolimbic dopamine cells belong to an incentivesystem that is recruited whenever an active behavioralresponse to an environmental stimulus isrequired. Still, the ‘meaning’ of mesolimbic dopamineactivity in different situations may range all theway from ecstasy to panic. It all depends on activitiesthat are going on in other parts of the brain at thesame time.The serotonin system is another example. Accordingto P&P, animals appear to be “relaxed, satisfiedand confident” when serotonin is high, but they alsomention that knockout mice with markedly reducedserotonin release are less fearful in situations whereanimals normally exhibit heightened fear responses.The situation is confusing because serotonin releaseis affected in many other situations as well. It participatesin the regulation of REM sleep (MONTI/MONTI2000), and the effects of fear-inducing and stressfulstimuli on the serotonin system are so variable andsituation-dependent that any speculation about aunitary function for this neurotransmitter seemshopeless (CHAOULOFF 2000). Serotonin seems to haveso many functions that we cannot assign it to a ‘fearmodule’, a ‘sociality module’, a ‘relaxation module’,or a ‘sleep module’.Perhaps the closest subcortical approximation toa function-specific module that evolved in responseto a specific environmental challenge is the systemof conditioned fear described by LEDOUX (LEDOUX1996). In this case the input is an association betweena sensory stimulus and an unpleasant outcome,and there are well-defined, hard-wired outputsinto the somatomotor, autonomic, endocrine,and possibly cognitive systems. Presumably this systemevolved as a solution to a recurrent adaptiveproblem: to avoid situations in which unpleasantnesshas been experienced in the past. Although itaccepts cognitive as well as sensory input, it operatesautomatically and is not easily controlled by the cognitivesystem, as evidenced by the difficulty of treatingphobic patients.Taken together, the most reasonable model is thatthe brain does have adaptively meaningful hardwiredconnections that function in a modular fashion:reflex-like and instinct-like. In typical cases,such stimulus–response arcs have distinct circuitriesfor sensory analysis, such as the ‘face cells’ in theventral temporal lobe, and motor circuitries such asthe ‘smile center’ in the cingulate cortex. Hard-wiredcircuitries that mature with minimal need for specificsensory inputs—although they may depend ontrophic influences from their afferents—are moretypical for subcortical areas but do occur in corticalregions as well, especially in and around the sensoryEvolution and Cognition ❘ 34 ❘ 2001, Vol. 7, No. 1