The Simon effect with conventional signals: a time-course analysis.

The Simon effect consists of a faster and a more accurate performance when spatial responses correspond to irrelevant-spatial stimuli than when they do not. The time course of the Simon effect was investigated using centrally presented conventional signals (arrows and spatial words) conveying spatial information through iconic-symbolic (Experiments 1 and 2) and semantic (Experiment 3) codes. Time-demanding object-inherent and semantic spatial codes were generated for arrows and words, respectively. This resulted in Simon effects increasing in size across increasing response times (RTs). However, different onsets of the Simon effect were displayed across RT distributions. For arrows, the Simon effect was already significant at the fastest RT intervals, providing clear evidence that they are distinctively more effective directional indicators compared to words.