S-R COMPATIBILITY AND RESPONSE SELECTION

In serial stage models, perception and action are usually thought to be linked to each other by an S-R translation mechanism. However, phenomena of S-R compatibility suggest a more direct relationship between perceptual and action domains. We discuss behavioral and psychophysiological evidence that irrelevant stimulus information automatically activates response codes, but then decays over time. In a series of reaction time studies and electrophysiological experiments, we investigated both temporal and functional properties of the assumed automatic response activation process. We found that the amount of interference due to irrelevant spatial information depends upon how long its availability precedes that of the information relevant for response selection. This indicates that response activation decays rather quickly. If response-relevant and irrelevant spatial information are simultaneously available, electrophysiological measurements show that automatic activation of the spatially corresponding response rises soon after stimulus onset, but then dissipates and gets replaced by the activation of the response indicated by the relevant stimulus attribute. We conclude that these findings do not support a pure translation account, but rather suggest the presence of two parallel and (at least partially) independent routes from perception to action: A direct route, allowing for automatic activation of response codes if stimulus and response features overlap, and an indirect route linking S and R codes in an arbitrary manner. Via the direct route responses may be primed independent of task-specific contingencies, while the correct response is selected via the indirect route. This use suggests that (a) the transmission of stimulus information to response stages does not (fully) depend on task relevance and that (b) different stimulus features can be transmitted asynchronously and independently from one another.