Shared mechanisms underlying the location-, word- and arrow-based Simon effects.

A left or right keypress response to a relevant stimulus attribute (e.g., color) is faster when irrelevant left or right stimulus-location information corresponds with the correct response than when it does not. This phenomenon, known as the Simon effect, is obtained not only for physical locations, but also location words "left" and "right" and left- or right-pointing arrows. However, these location-, word-, and arrow-based Simon effects show different patterns in the reaction-time (RT) distributions, as evident in delta plots. In the present study, we employed procedures, analysis of survival curves and divergence point analysis, which have not previously been applied to the Simon effect, to investigate differences in time course of these various Simon effects in more detail. Also, we examined whether the diffusion model for conflict tasks (DMC), which assumes that automatic activation of task-irrelevant information occurs in a pulse-like function, can capture not only features of the RT distributions for the location-based Simon effect, to which it has been fit previously, but also features of the word- and arrow-based Simon effects, to which it has not. Results showed different survival curves and earliest, maximum, and latest divergence points for the three Simon effects, but DMC was able to capture the basic features of the RT distributions reflected by delta plot and survival curves for all effects. The results imply that the location-, word-, and arrow-based Simon effects have shared mechanisms, although they have different RT distributions.