Page 47 - Deep Learning

30 Introduction

The exercise of visualizing something that is not present proves that mind
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is representational. The visual image – the state of mind that endures dur-
ing visualization – is a representation. The subjective experience of the image
is real to the person whose experience it is and so cannot be argued away or
declared nonexistent. Something that refers to some other thing is by defini-
tion a symbol or a representation of that other thing. If there were no mental
representations, the exhortation to visualize the Eiffel Tower would be mean-
ingless and impossible to follow, but it is not. When I ask a hundred students
in a lecture class to close their eyes and visualize a peacock on a lawn, none of
them raises his hand to ask what I mean by this. The conscious experience of
visualizing, of deliberately representing something in the mind’s eye, is familiar
to all but a few. The latter usually say they think “in words.” They do not mean
by this that they do not represent, but that they think with a different type of
mental representation that is closer to language than to pictures. Laboratory
experiments have confirmed the ancient claim that visualized information
is remembered better than information represented in silent speech, so the
choice of representation has measurable consequences. Representation is no
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mere epiphenomenon.
The ability to represent underpins many characteristics and powers of
our cognitive system. Our perceptual representations – representations of
the immediate present – constitute a buffer between the impact of physical
stimuli on our sensory organs and our decision making. Moths fly into flames
because their eyes are connected to their wings in such a way that when one
eye receives less light than the other, the wing on the shadowed side flaps faster,
thus causing a course adjustment that leads the moth toward the light and its
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own destruction. If moths were conscious, they would presumably scream in
agony as they inexorably flap themselves into a flame, unable to override the
causal connection between their eyes and their wings. Human beings are not
wired in this way; physical stimuli do not cause our actions. Instead, physical
stimuli give raise to perceptual representations. Our decisions, and hence our
actions, are determined by processes over those representations. The ability to
represent rather than react to perceptual input provides us with a certain level
of stimulus independence, a central characteristic of human cognition empha-
sized by such otherwise different thinkers as Donald O. Hebb and Jerome S.
Bruner. 17
Representations are equally necessary for dealing with the past and the
future. Without representation, we could not have memory, because the past
cannot be present – a paradox – but only represented in the present. A mem-
ory representation exists in the present, although that which is represented by