Page 393 - Deep Learning

376 Conclusion

created when the person acts vis­à­vis that environment. The causal chain thus
turns back on itself, and the loop is closed without an endless regress. The
circular relation between elementary representations, higher­order represen­
tations, action and the environment constitutes a dynamic system that never
settles.

Amplified Propagation of Point Changes

A change at one point in the cognitive system propagates upward through the
layers of processing. The fate of the propagation depends on the exact position
of the choice point in the system and how it is linked to other such points.
When there is a change at a particular point in the system – a redistribution
of activation over alternatives in problem perception, a restriction of range
of a single rule of action or an increase in the estimated subjective utility of
a belief – that change affects what is forwarded in the propagation process.
A change at point X might have little or no consequence, if the difference
between the new and the old is absorbed at the next level. A unit X might rise
above the relevant threshold and pass its results on to a higher unit Y, but Y
itself might remain dormant for lack of activation, so the change at X goes no
further. such dampened propagation might cross several layers of processing
before it fades. in the normal case, the propagation process supports stability
by filtering out perturbations.
in other cases there is amplified propagation, popularly known as a but­
terfly effect. As processing moves forward again after a revised choice at some
unit in layer N, it will potentially affect all subsequent layers by feeding each
one slightly different inputs than before. A small change at layer N can grow in
magnitude at each successive layer. The end product is a qualitatively different
representation of the situation or task at hand. in creativity, the point change
propagates upward in the perceptual system, possibly resulting in a represen­
tational change, but the effects do not end there. A changed representation
retrieves different knowledge structures from memory, which in turn means
that the search process proceeds through a different space, possibly resulting
in a previously unreachable solution. in skill acquisition, a point change –
the specialization of a single rule – propagates forward in time: Because the
change causes a switch in the sequence of rule firings at some point, the future
sequence of rule firings will diverge more and more from the path that the
system otherwise would have taken. in belief formation, a switch in a single
truth value might start a wave of truth value re­assessments that rolls through
the entire belief base.