ABSTRACT
In studies of any complex behavior the choice of model system influences the results and their interpretation. Generally, of course, the major interest of the human experimenter is to shed light on humans. The shortest route to this goal would seem to be either to study humans themselves or, to take advantage of the ease of manipulating and controlling experimental variables, to study animals that closely resemble humans. The findings in such animals would intuitively seem to be more directly relevant to humans than studies of organisms that are not as obviously close to us. It would be common sense to expect results from studying closely related mammals to lead more quickly to clinical application than studies of animals that are evolutionarily remote from humans (e.g., invertebrates such as flies and worms). However, historically, pragmatic issues such as ease and cost of obtaining and maintaining animals have often dictated that simpler animals be used. Furthermore, in order to reduce the complexity of the system, some fields have sacrificed resemblance to humans and have used reduced preparations, ranging from anesthetized or decerebrate mammals to slice preparations and the study of cells in culture. As an example, it is obviously impossible to assert that a small group of cells or a brain slice learns and remembers in a fashion that strictly resembles the process that occurs in a human learner. Nonetheless, the field of learning and memory has long accepted the limits of such systems. For example,
they have drawn cautious parallels between the electrophysiological phenomenon of long-term potentiation in brain slices or simple reflex behaviors in the sea slug Aplysia and the process of human learning and memory (1,2).
