..."there was less similarity between the response pairs comprising the PA list than there was between the response alternatives presented during the practice trial. Consequently, the anticipation of control developed from experience with the practice trial could have been reduced when the subjects chose the response words for the PA trials. It is this reduction in perceived control which is assumed to be responsible for the failure to obtain the predicted differences in PA performance between Choice and Force subjects. One method of testing the above explanation would be to introduce the experimenter's request to choose only preselected response words during the practice trial, thereby reducing the possibility of subjects experiencing a reduction in perceived control later in the experiment."