Page 53 - Deep Learning

36 Introduction

have occurred at that time. The memories that are retrieved in some period
of time constitute a small subset of all the memories that could have been
retrieved during that period, and the inferences drawn are few compared to
the many inferences the person could have drawn. A pure distributed view
implies that what is selected in one area of cognition is independent of what
is selected in another, because there is no center to coordinate the different
selections. But when we are engaged in a task, our cognitive processes work
in concert, with attention being allocated in such a way as to select the infor-
mation in our environment that enables our memory processes to retrieve
exactly the knowledge that our reasoning processes need to decide which
action to perform next.
Furthermore, the parallelism that invites the distributional view is limited.
It is true that perception, memory retrieval, reasoning and decision making
are intertwined and happen in parallel, but it is equally true that I, as a per-
son, do one thing at a time: make breakfast, get dressed, teach a class, answer
e-mail, revise a book chapter and so on. Although cognitive processes occur
in parallel, intentional actions are, by and large, carried out sequentially. Even
when we appear to be doing two things at once, as in using a cell phone while
driving, careful measurements show that such situations are better understood
in terms of rapid switching back and forth between the two tasks rather than
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in terms of true parallelism. Only when two simple, repetitive perceptual-
motor tasks have been practiced over and over again can they be carried out
in a truly parallel manner. Such rare exceptions aside, intentional action is
sequential.
Action is also organized over long periods of time. Consider a plan for a
vacation trip or for attending college. Plans of this sort coordinate hundreds or
even thousands of actions, each underpinned by multiple cognitive processes,
in the service of a goal – a college degree, a comfortable retirement and so
on – that might be several years into the future. It strains credulity that such
sustained projects happen as side effects of nothing but local interactions and
distributed processes.
The conclusion is that something coordinates the various cognitive pro-
cesses in the service of purposeful action. The main task of this control structure
is to resolve conflicts. At each moment in time, there are multiple processes
that could run, multiple memories that could be retrieved, multiple inferences
that could be drawn, multiple goals that could be set and multiple actions that
could be carried out next, so the flow of cognition requires ongoing evaluation
of options and continuous choices as to which processes to execute. This is
known as conflict resolution.