Ziessler, M. 1 & Nattkemper, D. 2
1 Department of Psychology, Liverpool Hope University, Liverpool, United Kingdom
2 Department of Psychology, Humboldt University Berlin, Berlin, Germany
It has been argued that the preparation of an action includes the anticipation of its proximal and distal effects (forward models). In turn, the selection of actions is assumed to be based on the anticipated effects (inverse models, ideomotor principle). Evidence for the anticipation of action effects comes mainly from experiments in which the effects were actually presented. However, it can be argued that this evidence is an artefact of the method; effect codes were only activated because the effects were presented as external stimuli. Therefore we cannot conclude from these experiments that response preparation would normally include anticipation of effects. We present new experiments avoiding this problem. Participants first learned effects of key-pressing responses (the appearance of hand gestures on the screen). In the following test phase participants were asked to withhold their response to the target stimulus until a go-signal appeared (picture of an object). The go-signal was either compatible or incompatible with the learned effect. Responses were faster in compatible trials. This is strong evidence for an activation of effect codes as part of the preparation of the responses. Only then the compatibility between go-signal and effects could affect response times.