The preparation of actions and parameters of action: A fixed or variable process?

Some information processing models consider the selection of an action plan (deciding what to do) and the parameterization of the action (deciding how to do it) as separate stages in movement preparation. Further, these models consider the stages to occur in a fixed order, whereby the selection of an action precedes the parameterization of the action. Five experiments are reported that tested this position. The first four experiments adopted a variation of Rosenbaum's (1980) precuing technique such that, under varying conditions, different amounts and types of advance information were provided to the subject, leaving only the unspecified action or parameter to be supplied following the imperative signal. The critical finding from each study was that the time to specify an action and the time to specify a parameter were equivalent. In experiment 5, similar results were obtained using a response priming paradigm (Rosenbaum and Kornblum 1982). The results of all five studies failed to support a fixed-order model of movement preparation and are more consistent with a variable-order model. The implications of these findings for other models of movement preparation are discussed.