The influence of stimulus array on training of a speeded response.

We conducted two experiments to study the training of speeded responses to stimuli in a clock face array. Participants were trained on one clock face and later tested on either the same or a different clock face. The clock faces varied along 3 dimensions of change (left-right flip, up-down flip, and 180 degrees rotation). Skill acquisition was reflected in decreases in overall, initiation, and movement response times in the training and test phases except that movement time reached an asymptote during training and did not decrease further during test. Test performance was best when training and test used the same clock face and worst when the training to test change involved an up-down flip. The transition to different clock faces was consistent with an interpretation based on the violation of expectations about target positions acquired during training. Consistent trial-by-trial feedback led to better initiation time but not movement time during training than periodic feedback, but this effect did not persist into the test phase.