Initiating the formalization of theories of cognitive aging.

Although the relevant knowledge base is still impoverished, the time may be appropriate to attempt to develop and investigate formal models of cognitive aging that incorporate explicit mechanisms to account for age differences frequently observed in measures of cognitive functioning. An initial model based on an associative network metaphor is described, in which age declines in fluid or process aspects of cognition are attributed to a reduction in either the number of simultaneously active nodes, the maximum allowable activation, or the rate of propagating activation between nodes. Results from a computer simulation are consistent at a first level of approximation with many cognitive aging phenomena, and the model is shown to provide a plausible account of age differences in an area that has previously resisted explanation. Although this particular model is only one of many that could be formulated at the present time, it is argued that more rapid progress in theoretical understanding of cognitive aging phenomena will be achieved by attempting to specify one's assumptions and hypotheses in a formal and explicit manner.