Mind, Body, World- Foundations of Cognitive Science, 2013a

In his pioneering work on simulating the flight of a flock of artificial birds,
called boids, Reynolds (1987) created lifelike flocking behaviour by having each
independently flying boid adapt its trajectory according to three simple rules: avoid
collision with nearby flock mates, match the velocity of nearby flock mates, and
stay close to nearby flock mates. A related model (Couzin et al., 2005) has been successfully
used to predict movement of human crowds (Dyer et al., 2008; Dyer et al.,
2009; Faria et al., 2010).
However, many human social interactions are likely more involved than the
simple behavioural loops that defined the social interactions amongst Grey Walter’s
(1963) Tortoises or the flocking behaviour of Reynolds’ (1987) boids. These interactions
are possibly still behavioural loops, but they may be loops that involve processing
special aspects of the social environment. This is because it appears that the
human brain has a great deal of neural circuitry devoted to processing specific kinds
of social information.
Social cognition is fundamentally involved with how we understand others
(Lieberman, 2007). One key avenue to such understanding is our ability to use and
interpret facial expressions (Cole, 1998; Etcoff & Magee, 1992). There is a long history
of evidence that indicates that our brains have specialized circuitry for processing
faces. Throughout the eighteenth and nineteenth centuries, there were many
reports of patients whose brain injuries produced an inability to recognize faces
but did not alter the patients’ ability to identify other visual objects. This condition
was called prosopagnosia, for “face blindness,” by German neuroscientist Joachim
Bodamer in a famous 1947 manuscript (Ellis & Florence, 1990). In the 1980s, recordings
from single neurons in the monkey brain revealed cells that appeared to be tailored
to respond to specific views of monkey faces (Perrett, Mistlin, & Chitty, 1987;
Perrett, Rolls, & Caan, 1982). At that time, though, it was unclear whether analogous
neurons for face processing were present in the human brain.
Modern brain imaging techniques now suggest that the human brain has
an elaborate hierarchy of co-operating neural systems for processing faces and
their expressions (Haxby, Hoffman, & Gobbini, 2000, 2002). Haxby, Hoffman, and
Gobbini (2000, 2002) argue for the existence of multiple, bilateral brain regions
involved in different face perception functions. Some of these are core systems that
are responsible for processing facial invariants, such as relative positions of the eyes,
nose, and mouth, which are required for recognizing faces. Others are extended
systems that process dynamic aspects of faces in order to interpret, for instance,
the meanings of facial expressions. These include subsystems that co-operatively
account for lip reading, following gaze direction, and assigning affect to dynamic
changes in expression.
Facial expressions are not the only source of social information. Gestures and
actions, too, are critical social stimuli. Evidence also suggests that mirror neurons in
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