The Ash Twins Blog

Wilson (2006) of Creighton University introduces a three-part framework for integrating empirical data from evolutionary behavioral neuroscience with evolutionary game theory models. He begins with a description of the framework in neuroscience terms:

MacLean’s neuroethological conceptualization essentially describes three main levels of archetypal neuromental circuitries upon which our sociality is based. It further is compatible with two opposing algorithms – one for self-maintenance (agonic competition) and the other for care-giving (or hedonic affection) – operating with rather more refinement as three main assemblages arose in succession (Price, 1988; Gilbert, 1992; Gilbert et al., 1995). This evolutionary neuroethological model is currently the only synthesis that renders the vastly larger and profoundly complex body of neuroscientific data as a valid and workable schematic (Cory, 1999, 2003; Cory and Garnder, 2002; Wilson, 2002). That this schematic describes a coherent, global state mechanism is increasingly important for much social science if the latter is to achieve reliable and valid theoretical or practical progress – much less subsume and reconcile the huge influx of pertinent neurobiological and evolutionary facts underlying behavior.

The first of these three circuitries MacLean dubbed the Reptilian complex (‘R-complex’). The R-complex is constituted of the brain stem and midbrain (along with a very small and primitive part of forebrain). These anatomical structures and behavioral functions evolved with early coldblooded vertebrates and became fully instantiated in the essentially asocial, self-maintaining circuitry of the reptilian line ancestral to humans.

The second of these circuitries MacLean dubbed the ‘Paleomammalian complex’ (or, as an alternative, often retaining a slightly modified extant term, the ‘limbic system’). The paleomammalian limbic system comprises a more recently elaborated assemblage anatomically bordering the earlier R-complex. MacLean’s limbic system is a refinement of the ‘Lobe Limbique’ of Broca, who so named it as it was at the edge (or limbus) of the old brain (Broca, 1878; Pribram, 1958; Harlow and Harlow, 1965). The earliest aspects of limbic system evolution trace to the transitional emerging from the reptilian line 300 million years ago.

The paleomammalian complex became fully instantiated with the more comprehensive and complete mammalian neural structures and behavioral functions that evolved with remarkable rapidity some 120 million years ago. Within only 10 million years or so were laid down the exceptionally complex neuroendocrine anatomical physiology that facilitates all classical mammalian behavior ranging from internal fetal development, parturition, nursing of infants, parent–infant bonding, and continuous interactive, reciprocal ‘warm-blooded’ social life. . .

Interestingly, the earliest feature of the limbic system is the thalamocingulate gyrus that first evolved to enable ancient mammalian mothers to identify the distress cries of their off-spring (Clutton-Brock, 1991;Wilson, 2002). Later if equally critical adaptations of the paleomammalian complex allows for the emergence of play – reciprocal and convivial social interaction – among mammals as a more general social extension of kinship bonding. Thus, the parent–infant bond that blends self-preservation genetic kinship circuitry with affectional circuitry in a reciprocal social relationship is, in fact, the foundation for extended social reciprocity (‘eusociality’ and altruism) that underpins human social life (Piaget, 1971; Wilson, 1975; Plutchik, 1984; Zajonc, 1980; Panksepp, 1998; Carter and Keverne, 2002; Gardner and Wilson, 2003).

Both the archetypal reptilian and early mammalian circuits are necessary to human sociality. The second was not possible without the first and certainly much interactivity has evolved. Mammalian social circuitry rests upon a basis of self-maintaining circuitry in a manner that reflects Maslow’s ‘Hierarchy of Needs’ with safety first (Maslow, 1971). Moreover, to be favored in Darwinian selection and passed in the genome, their interplay must keep within survival limits. Indeed, even before more recent advances in neuroscience and evolution, ethologists such as Harlow and Harlow (1965), Chance (1967) and Bowlby (1969, 1980) earlier posited such eusociality as a central element in their concepts of affectional systems and attachment, respectively.

MacLean identified a third level of circuitry the ‘Neomammalian complex’. This neomammalian complex is anatomically and behaviorally synonymous with the limbic cortex as it extends the capabilities of the two older circuits more deeply canalized in evolution. That is, the cortical elements of the limbic system allow increasingly sophisticated and frequently conscious analysis of a rational-emotive type. Moreover, the limbic cortex emotive rationality mediates essentially opposing behavioral options.
Such analytic mediations are often enriched via domain-specific input from higher cortical centers, e.g., primary, secondary and tertiary association neocortex that are the basis for language, numeracy, abstract reasoning (and other talents such as musicality and sensory synesthesia). The considerable interaction between the limbic system and neocortex is a factor that has greatly extended reciprocally interactive social life, including self-consciousness, romance, charisma, Machiavellian intellect and much else (Gilbert et al., 1995; Cosmides and Tooby, 1992).

Between the most primitive vegetative neural apparatus in pre-chordates and the most recent and abstract domain-specific modules of neocortex, there are three major phylogenetic levels wherein brain and mind modulate social behavior. These three levels mediate proximal aspects of social rank competition that, ultimately, allocate resources consistent with Darwinian fitness (Darwin, 1859). The later, more advanced of these neuromental assemblages are less ‘hardwired’ and thus can better adjust phenotypy in the face of environmental challenges individuals experience in the course of ontogenic development (Wilson, 1998). . .

Wilson then integrates this three-part model into a game-theoretic hawk-dove model of cooperation:

Game theory models R-complex in terms of ‘Ritualized Agonistic Behavior’ (RAB), as is appropriate for basic algorithms of ‘fight or flight’, evolved some 250 million years ago (Lorenz, 1981; Price, 1988; Maynard Smith, 1982). Strong, strident animals maintain territory or other resources to influence weaker, cowering rivals. This is via displays that are entirely instinctual as driven by the non-conscious interactions of the autonomic (automatic) nervous systems of two rivals. These instinctive behaviors are mediated by circuits enervated by the earliest and most basic vertebro-reptilian types of neurotransmitter receptors (e.g., dopamine 1; serotonin 1; see Wilson, 2002). The tug and pull in specific individuals alters the balance of such neurotransmitters in patterns that predictably predispose to a higher or lower status in the pecking order.

Game theory models the paleomammalian level in terms of ‘Resource Holding Potential’ (RHP), as is appropriate for more subtle algorithms of ‘dominance or submission’ evolved some 120 million years ago (Parker, 1984; Price, 1988; Maynard Smith, 1982). Here, confidently optimistic animals acquire influence over meek counterparts via emotionally charged displays driven by sub-conscious interactions of the paleolimbic systems of the dyad. These emotive behaviors are mediated by circuits enervated by new mammalian subtypes of neurotransmitter receptors. The tug and pull in specific individuals affects the balance of neurotransmitters in patterns that predictably predispose to higher or lower ranges of mood and affect (Wilson, 2002).

Game theory models the Primatohumanoid level in terms of ‘Social Attention Holding Potential’ (SAHP), as is appropriate for overtly affiliative algorithms of ‘attraction or avoidance’ evolved over the past 60 million years (Gilbert, 1992; Maynard Smith, 1982). Here, affably charismatic persons win the esteem of others in whom they inspire confidence. This is via displays that are social and intellectual as driven by conscious interactions of the limbic and neocortices of familiars. These rationally creative behaviors are mediated by circuits enervated by the newest neomammalian, primate and hominoid subtypes of neurotransmitter receptors (e.g., humans have more than 16 subtypes of receptors for serotonin laid out in highly specific circuits). Here, the tug and pull in specific individuals alters the balance of such neurotransmitters in patterns that predictably predispose to higher or lower ranges of sociability, charm and influence (Wilson, 2002).