A DYNAMIC-MODEL OF REACTION-TIME IN A SHORT-TERM-MEMORY TASK

In this article we hypothesized that the trial to trial variability in speed of access to recently presented information is deterministic in nature and that it reflects important properties of immediate memory. Application of analytic techniques emerging from the science of nonlinear dynamical systems to data obtained from the Sternberg (1966, 1970) short-term memory task corroborates the view. A simple nonlinear difference equation, consistent with fuzzy-trace theory (Brainerd & Reyna, 1992), was then proposed to describe the dynamics underlying reaction time (RT) on the Sternberg task. The model posits that RT is a function of the interaction of two control parameters: susceptibility to interference (SI) and episodic activation (EA). Evaluation of the model indicated an exceptionally good fit with the raw empirical observations. Age comparisons of the model parameters revealed that adults exhibited higher levels of SI and EA. Although the finding that adults exhibited higher levels of SI than children runs counter to theory and other empirical results, further analysis revealed that adults exhibited lower levels of SI relative to EA than children. Thus, children may exhibit slower disintegration of verbatim memory traces than adults due to interference; however, adults may be more efficient at redintegrating verbatim memory traces than children. (C) 1994 Academic Press, Inc.