Title

Rules and more rules: The accessibility of productions in highly trained younger and older adults

Date of Award

2003

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Advisor(s)

William J. Hoyer

Keywords

Young adults, Anderson's ACT-R model, Aging, Older adults

Subject Categories

Developmental Psychology | Psychology | Social and Behavioral Sciences

Abstract

Under the tenets of Anderson's ACT-R model (Anderson & Lebiere, 1998), an information-processing system is governed by a library of production rules which specify, for a given stimulus configuration, the requisite processing procedure. Access to productions is postulated to be in parallel. We tested this postulate by measuring production selection and execution as a function of the size of the production library (varied from set size 1 to 4), using arithmetic-like rules that operated on digit stimuli. After five sessions of training, the ACT-R prediction was confirmed for most younger and a few older participants: beyond the special case where only one production was active, increases in set size had no further effect on response time. The step increase from size 1 to size >1 was substantial and was represented by an analysis of RT distributions as a shift in all three ex-Gaussian distribution parameters, mu , sigma , and tau . It is suggested that the step size 1 to size >1 reflects either the engagement of processes active in cognitive control or the manifestation of a limited capacity system. The form of the step function can also be characterized in terms of task switch costs (Rogers & Monsell, 1995), in which case there were constant global and local switch costs attached to the maintenance of any production set >1. In older participants, the increase in RT was negatively accelerated and all of the individuals had equivalent RTs for set size >2. The curvilinear form of the older adult function was largely determined by global switch costs and a corresponding shift in the mu parameter, which has been implicated in peripheral processing (Balota & Speiler, 1999). Preliminary studies also suggest that in either age group, non-"homogeneous" rule sets may be less well-behaved.

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