Response strategies and the Simon effect

The study investigated whether the Simon effect, and its facilitation and i nterference components, shows up in reaction time (RT) or in movement time (MT), depending on the response strategy. Experiment 1 replicated a study b y Hietanen and Rama. Subjects had to press one of two lateralised keys in r esponse to one of two stimuli. The stimuli were presented in the center (ne utral condition) or to the left or right side (corresponding or non-corresp onding conditions). To press the response key, a reaching movement was nece ssary, and both RT and MT were recorded. One group of subjects showed an RT facilitation effect and an MT interference effect. Another group of subjec ts showed both MT facilitation and MT interference effects. It was hypothes ized that the two groups used different response strategies. In Exps. 2 and 3, the subjects were explicitly instructed to use the two strategies that were hypothesized for Exp. 1. The results showed that whether facilitation and interference manifest themselves in RT or MT depends on the response st rategy adopted by the subjects.