Advance preparation of motor actions is important if accurate responses to external events are to be made with minimal delay. Such preparation requires selection of appropriate actions and specification of how to perform them. As environmental conditions change constantly, confining preparation to one action (and one way of doing it) could be disadvantageous, and evidence does indeed suggest that multiple responses (and multiple ways of executing them) can be prepared in advance. Competitive activation and inhibition processes determine the selection of the appropriate response, and low-level components of these processes have been studied successfully using the masked prime (MP) paradigm. In comparison, relatively little is known about the role of similar processes in determining the parameters of response execution. It is sometimes assumed, but not yet demonstrated, that parameterization processes are organized similarly to those governing response selection. If this is the case, then parameterization should behave similarly to selection in the MP paradigm. In order to investigate this, however, the MP paradigm will have to undergo substantial changes (eg being adapted to prime continuous parameters rather than binary alternatives). The present project investitages whether such adapations are possible.