Neuro-Cooperative Mechanics

Ian Goddard igoddard at
Mon Aug 12 20:41:20 EST 2002


Proc. Natl. Acad. Sci. USA, 10.1073/pnas.122352699

Selective impairment of reasoning about social exchange 
in a patient with bilateral limbic system damage

Valerie E. Stone, Leda Cosmides, John Tooby, Neal Kroll, 
and Robert T. Knigh

[ affiliations cut for brevity, see URL above ]

Social exchange is a pervasive feature of human social life. Models
in evolutionary biology predict that for social exchange to evolve
in a species, individuals must be able to detect cheaters
(nonreciprocators). Previous research suggests that humans have a
cognitive mechanism specialized for detecting cheaters. Here we
provide neurological evidence indicating that social exchange
reasoning can be selectively impaired while reasoning about other
domains is left intact. The patient, R.M., had extensive bilateral
limbic system damage, affecting orbitofrontal cortex, temporal pole,
and amygdala. We compared his performance on two types of reasoning
problem that were closely matched in form and equally difficult for
control subjects: social contract rules (of the form, "If you take
the benefit, then you must satisfy the requirement") and precaution
rules (of the form, "If you engage in hazardous activity X, then you
must take precaution Y"). R.M. performed significantly worse in
social contract reasoning than in precaution reasoning, when
compared both with normal controls and with other brain-damaged
subjects. This dissociation in reasoning performance provides
evidence that reasoning about social exchange is a specialized and
separable component of human social intelligence, and is consistent
with other research indicating that the brain processes information
about the social world differently from other types of information.


  Out-of-Body Explanation:


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