Saul Sternberg , Ph.D.
Professor of Psychology
University of Pennsylvania
Philadelphia, Pennsylvania
November 7, 1996

Parallel and Serial Operations

Collaborative work by Teresa Pantzer and Saul Sternberg
University of Pennsylvania, Philadelphia

What operations are used to identify the characters in a visual display, and how are these operations arranged in time? These questions have attracted experimental psychologists since their field began, and different answers have been offered, based on the data from various paradigms. To investigate these issues, we used a task in which subjects under time pressure had to recite the names of all the items (numerals) in a briefly-presented visual array. We manipulated the number of items in the array and their legibilities.

We found that degrading one or more items produces dramatically different timing patterns, depending on type of degradation. Superimposition of a grid influences primarily a parallel component (alpha; contour formation?) of the encoding process, whereas disorientation influences primarily a serial component (gamma; memory interrogation?). Data patterns that result when the two forms of degradation are combined within and across items also require us to postulate a third component (beta; feature extraction?) that occurs between the alpha and gamma components. The betas for different items occur serially, probably in the same order as the reciting order. Within an item, alpha, beta, and gamma appear to be arranged in series. Across items, alpha and beta can overlap: The beta operation for one item can start before the alpha operations for other items have been completed. This overlap property permits the parallel alpha process to reveal the seriality of the beta process.