On the translation of some stimulus features to response force

Romaiguère et al. (1993) reported an stimulus-response (S-R) experiment in which the participants had to respond to bright or dim stimuli by pressing a key strongly or weakly. Reaction time (RT) for a compatible S-R assignment (bright-strong; dim-weak) was substantially shorter than for an incompatible S-R assignment (dim-strong; bright-weak). This effect was explained as a direct translation of stimulus intensity to response force (RF). In the present study, we looked for other stimulus features that could be directly transferred to RF. We investigated stimulus size (large/small), vertical location (above/below), and brightness (bright/dim). Delays of RT for incompatible trials were found in case of brightness and size, but not location. In a second experiment, we tested whether such a direct translation might even cause changes of spontaneous RF. Without being instructed about RF, participants made simple reactions to stimuli which differed either in location, size or brightness. Indeed, stimulus size affected RF: larger stimuli were associated with stronger responses. In contrast, brightness had no effect. Thus, we replicated and extended Romaiguère et al.'s (1993) finding. However, the direct-translation account for RF variations received only partial support from our data.