Who Needs Emotions? The Brain Meets the Robot

350 conclusions
mediated by distributed processes of competition and cooperation. There
need be no one place in the brain where an integrated representation of space
plays the sole executive role in linking perception of the current environment
to action.
Dean, Redgrave, and Westby (1989; see also Dean & Redgrave, 1989)
used a study of the rat informed by findings from the study of the frog to
provide an important bridge between frog and monkey. Where most research
on the superior colliculus of cat and monkey focuses on its role in saccadic
eye movements—an approach behavior for the eyes—Dean et al. looked at
the rat’s own movements and found two response systems in the superior
colliculus which were comparable with the approach and avoidance systems
studied in the frog and toad. We thus see the transition from having the
superior colliculus itself commit the animal to a course of action (frog and
rat) to having it more often (but not always) relinquish that role and instead
direct attention to information for use by cortical mechanisms in committing
the organism to action (e.g., cat, monkey, and human). We now turn to
one system for committing the organism to action, that for grasping, and then
present an evolutionary hypothesis which links cerebral mechanisms for
grasping to those that support language.
The Mirror System and the Evolution of Language
Having looked at vision from a very general perspective, I now focus on two
very specific visual systems that are especially well developed in primates:
the system that recognizes visual affordances for grasping and the system
that recognizes grasping actions made by others. I shall then argue that these
systems provide the key to a system that seems specifically human: the brain
mechanisms that support language.
Brain Mechanisms for Grasping
In macaque monkeys, parietal area AIP (the anterior region of the intraparietal
sulcus; Taira et al., 1990) and ventral premotor area F5 (Rizzolatti
et al., 1988) anchor the cortical circuit which transforms visual information
on intrinsic properties of an object into hand movements for grasping it. The
AIP processes visual information on objects to extract affordances (grasp
parameters) relevant to the control of hand movements and is reciprocally
connected with the so-called canonical neurons of F5. Discharge in most
grasp-related F5 neurons correlates with an action rather than with the indi-