POTENTIAL BETWEEN BRAINS 243mostly limited to the benefi ts of foraging and predator avoidance. Never-
theless, the dynamics of their coordination are fascinating and have been
widely researched. Again, there has been much debate about how it actu-
ally happens. As Iain Couzin put it, “Decision- making by individuals
within such aggregates is so synchronized and intimately coordinated
that it has previously been considered to require telepathic communica-
tion among group members or the synchronized response to commands
given, somehow, by a leader.”^6
Some shoals are quite loosely aggregated. Others are more tightly
or ga nized, all moving at the same speed and in the same direction. Th en
the fi sh are said to be schooling. Fish schools move with the individual
members precisely spaced from one another and undertake complicated
maneuvers, as though under top- down regulation.
As with the social insects, though, there are no executive or supervi-
sory agents at work. All the group choreography is achieved by mecha-
nisms in individuals interacting with the structural dynamics emerging
in the group as a whole. Th e results include patterned be hav iors for
foraging and more complex ones for avoiding and confusing predators. In
the pro cess, they manage to avoid collisions between individuals, colli-
sions with obstacles, or breakdown in the coherence of the overall pat-
terns. Th e speed of reaction to predator attack suggests rapid transmis-
sion of information from one group member to another, initiating
changes of direction. Th ey then turn in concert, resulting in escape waves,
sometimes fanning out or using other tactics to confuse the predator.
As with the ant research, rather simple if- then rules of individual
be hav ior have been proposed to account for the composite integrity and
success of shoals or schools. For example: keep an eye on your immediate
neighbors, move in the same direction as your neighbors, and remain
close to them (but not too close). Th ese have formed the bases of
“individual- based modeling.” In truth, though, the actual behavioral
rules followed by individuals in fi sh shoals are still poorly understood.
Simple rules, like those just mentioned, have only been partially success-
ful in accounting for school be hav ior. So some researchers have proposed
that the “telepathy” emerges from self- organ izing dynamics, as in ant
colonies. As Naomi Leonard argues, “Th e dynamics of collective animal
be hav ior are typically nonlinear due to nonlinearities in individual
dynamics, nonlinearities in interaction dynamics, nonlinear coupling
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