Distributions of simple RT with single and double stimuli

Abstract

Two similar visual flashes spatially separated were used as stimuli in a simple RT experiment. The RT distributions of the single stimuli were compared to cases with paired stimuli applied simultaneously (or nearly simultaneously). Spatial separation of simultaneous stimuli induces parallel processing. After comparing single-stimuli RT distributions with double-stimuli RT distributions, it was concluded that a race model with independent parallel processing provides the better fit to the data as compared to dependent parallel processing or partially parallel processing. Scanning models as well as signal summation models had to be rejected. The serial structure of the processing of single stimuli allows for a description of an exponential and a residual distribution. The analysis presented in this study is of importance for the concept of stages in serial processing of more complicated stimuli. © 1977 Psychonomic Society, Inc.