Abstract
Previous research shows that planning and withholding an action to a stimulus (X1) can delay the response to a second stimulus (X2), if X2 is response compatible (requires the same response hand) with X1 (compatibility interference, CI). To explain CI, Stoet and Hommel (1999) proposed the Code Occupation Hypothesis (COH) which suggests that action planning may temporally integrate all components controlling planned actions, preventing any one of these action components from being readily available for another action until the current plan is executed/abandoned. CI occurs when responses to X1 and X2 are based on stimulus identity, and when X2 appears briefly. However, it is unclear whether CI occurs when the response to X1 is based on stimulus identity and the response to X2 is based on ego location. It is also unclear whether CI occurs when X2 is present when its corresponding response is executed. The present study tested the assumptions of COH by determining whether CI generalizes from identity-based actions (that require key presses) to location-based actions (that require pointing to a stimulus location on a touch screen). The presentation duration of X2 (250 ms vs. viewed until response) was also varied to determine if CI occurs independently of X2 duration. Observers planned a response to X1 and a response to X2 that required either the same hand (compatible) or different hands (incompatible). CI occurred when responses to X1 and X2 were identity based and the duration of X1 was 250 ms (Exp. 1). CI did not occur when the response to X2 was based on ego location (Exp. 2 & 4) or when X2 remained present during its corresponding response (Exp. 2 & 3). These findings conflict with the assumptions of COH. CI may occur only when both responses are identity based (and hence utilize the ventral stream) and/or when verbal recoding and rehearsal of the X2 response is required to accurately respond to X2 (Exp. 1).