Generalisation of unpredictable action-effect features: Large individual differences with little on-average effect.

Ideomotor theory suggests that selecting a response is achieved by anticipating the consequences of that response. Evidence for this is the response-effect compatibility (REC) effect, that is, responding tends to be faster when the (anticipated) predictable consequences of a response (the action effects) are compatible rather than incompatible with the response. The present experiments investigated the extent to which the consequences must be exactly versus categorically predictable. According to the latter, an abstraction from particular instances to the categories of dimensional overlap might take place. For participants in one group of Experiment 1, left-hand and right-hand responses produced compatible or incompatible action effects in perfectly predictable positions to the left or right of fixation, and a standard REC effect was observed. For participants in another group of Experiment 1, as well as in Experiments 2 and 3, the responses also produced action effects to the left or right of fixation, but the eccentricity of the action effects (and thus their precise location) was unpredictable. On average, the data from the latter groups suggest that there is little, if any, tendency for participants to abstract the critical left/right features from spatially somewhat unpredictable action effects and use them for action selection, although there were large individual differences in these groups. Thus, at least on average across participants, it appears that the spatial locations of action effects must be perfectly predictable for these effects to have a strong influence on the response time.