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

primitive form of spatial information is imagery, or whether images are constructed
from more primitive propositional codes (Anderson, 1978; Block, 1981; Kosslyn,
Thompson, & Ganis, 2006; Pylyshyn, 1973, 1981a, 2003b).
Even though classical cognitive science is functionalist in nature and (in the
eyes of its critics) shies away from biology, it also appeals to implementational
evidence in its study of memory. The memory deficits revealed in patient Henry
Molaison after his hippocampus was surgically removed to treat his epilepsy
(Scoville & Milner, 1957) provided pioneering biological support for the functional
separations of short-term from long-term memory and of declarative memory
from nondeclarative memory. Modern advances in cognitive neuroscience have
provided firm biological foundations for elaborate functional decompositions of
memory (Cabeza & Nyberg, 2000; Poldrack et al., 2001; Squire, 1987, 2004). Similar
evidence has been brought to bear on the imagery debate as well (Kosslyn, 1994;
Kosslyn et al., 1995; Kosslyn et al., 1999; Kosslyn, Thompson, & Alpert, 1997).
In the paragraphs above I have taken one tradition in cognitive science (the
classical) and shown that its study of one phenomenon (human memory) reflects
the use of all of the levels of investigation that have been the topic of the current
chapter. However, the position that cognitive explanations require multiple
levels of analysis (e.g., Marr, 1982) has not gone unchallenged. Some researchers
have suggested that this process is not completely appropriate for explaining cognition
or intelligence in biological agents (Churchland, Koch, & Sejnowski 1990;
Churchland & Sejnowski, 1992).
For instance, Churchland, Koch, & Sejnowski (1990, p. 52) observed that “when
we measure Marr’s three levels of analysis against levels of organization in the nervous
system, the fit is poor and confusing.” This observation is based on the fact that
there appear to be a great many different spatial levels of organization in the brain,
which suggests to Churchland, Koch, & Sejnowski that there must be many different
implementational levels, which implies in turn that there must be many different
algorithmic levels.
The problem with this argument is that it confuses ontology with epistemology.
That is, Churchland, Koch, & Sejnowski (1990) seemed to be arguing that Marr’s
levels are accounts of the way nature is—that information processing devices are
literally organized into the three different levels. Thus when a system appears to
exhibit, say, multiple levels of physical organization, this brings Marr-as-ontology
into question. However, Marr’s levels do not attempt to explain the nature of
devices, but instead provide an epistemology—a way to inquire about the nature
of the world. From this perspective, a system that has multiple levels of physical
organization would not challenge Marr, because Marr and his followers would be
comfortable applying their approach to the system at each of its levels of physical
organization.
Multiple Levels of Investigation 53