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

ole at the algorithmic level, for it provides the primitive operations from which
algorithms are created. Thus we would expect that the behavioural vocabulary used
for algorithms to also be applied to the architecture.
The special nature of the architecture means that additional behavioural
descriptions are required. A researcher must also collect behavioural evidence to
support his or her claim that some algorithmic component is in fact an architectural
primitive. One example of this, which appears when the ideas that we have
been developing in this chapter are applied to the science of human cognition, is
to conduct behavioural experiments to determine whether a function is cognitively
impenetrable (Pylyshyn, 1984; Wright & Dawson, 1994). We return to this kind of
evidence in Chapter 3.
Of course, the fundamental difference between algorithm and architecture is
that only the latter can be described in terms of physical properties. Algorithms
are explained in terms of the architectural components in which they are written.
Architectural components are explained by describing how they are implemented
by some physical device. At the implementational level a researcher uses a physical
vocabulary to explain how architectural primitives are brought to life.
An implementational account of the logic gates illustrated in Figure 2-1 would
explain their function by appealing to the ability of metal wires to conduct electricity,
to the nature of electric circuits, and to the impedance of the flow of electricity
through these circuits when switches are open (Shannon, 1938). An implementational
account of how a vacuum tube creates a relay of the sort illustrated in Figure
2-2 would appeal to what is known as the Edison effect, in which electricity can
mysteriously flow through a vacuum and the direction of this flow can be easily
and quickly manipulated to manipulate the gate between the source and the drain
(Josephson, 1961; Reid, 2001).
That the architecture has dual lives, both physical and algorithmic (Haugeland,
1985), leads to important philosophical issues. In the philosophy of science there
is a great deal of interest in determining whether a theory phrased in one vocabulary
(e.g., chemistry) can be reduced to another theory laid out in a different
vocabulary (e.g., physics). One approach to reduction is called the “new wave”
(Churchland, 1985; Hooker, 1981). In a new wave reduction, the translation of
one theory into another is accomplished by creating a third, intermediate theory
that serves as a bridge between the two. The functional architecture is a bridge
between the algorithmic and the implementational. If one firmly believed that a
computational or algorithmic account could be reduced to an implementational
one (Churchland, 1988), then a plausible approach to doing so would be to use the
bridging properties of the architecture.
The dual nature of the architecture plays a role in another philosophical discussion,
the famous “Chinese room argument” (Searle, 1980). In this thought
Multiple Levels of Investigation 49