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

connectionism. Many researchers assume that PDP networks acquire implicit
knowledge. For instance, consider this claim about a network that learns to convert
verbs from present to past tense:
The model learns to behave in accordance with the rule, not by explicitly
noting that most words take -ed in the past tense in English and storing this
rule away explicitly, but simply by building up a set of connections in a pattern
associator through a long series of simple learning experiences. (McClelland,
Rumelhart, & Hinton, 1986, p. 40)
One problem that immediately arises in using explicit rules as a mark of the classical
is that the notions of explicit rules and implicit knowledge are only vaguely
defined or understood (Kirsh, 1992). For instance, Kirsh (1992) notes that the distinction
between explicit rules and implicit knowledge is often proposed to be similar
to the distinction between local and distributed representations. However, this
definition poses problems for using explicit rules as a mark of the cognitive. This is
because, as we have already seen in an earlier section of this chapter, the distinction
between local and distributed representations does not serve well to separate classical
cognitive science from other approaches.
Furthermore, defining explicit rules in terms of locality does not eliminate connectionism’s
need for them (Hadley, 1993). Hadley (1993) argued that there is solid
evidence of the human ability to instantaneously learn and apply rules.
Some rule-like behavior cannot be the product of ‘neurally-wired’ rules whose structure
is embedded in particular networks, for the simple reason that humans can
often apply rules (with considerable accuracy) as soon as they are told the rules.
(Hadley, 1993, p. 185)
Hadley proceeded to argue that connectionist architectures need to exhibit such
(explicit) rule learning. “The foregoing conclusions present the connectionist with
a formidable scientific challenge, which is, to show how general purpose rule following
mechanisms may be implemented in a connectionist architecture” (p. 199).
Why is it that, on more careful consideration, it seems that explicit rules are not
a mark of the cognitive? It is likely that the assumption that PDP networks acquire
implicit knowledge is an example of what has been called gee whiz connectionism
(Dawson, 2009). That is, connectionists assume that the internal structure of
their networks is neither local nor rule-like, and they rarely test this assumption by
conducting detailed interpretations of network representations. When such interpretations
are conducted, they can reveal some striking surprises. For instance, the
internal structures of networks have revealed classical rules of logic (Berkeley et al.,
1995) and classical production rules (Dawson et al., 2000).
The discussion in the preceding paragraphs raises the possibility that connectionist
networks can acquire explicit rules. A complementary point can also be made
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