Dissociating Local and Global Levels of Perceptuo-Motor Control in Masked Priming

Masked prime stimuli presented near the threshold of conscious awareness affect responses to subsequent targets. The direction of these priming effects depends on the temporal characteristics of the prime-mask-target sequence. With short prime/mask-target intervals, benefits for compatible trials (primes and targets mapped to the same response) and costs for incompatible trials are observed. This pattern reverses with longer intervals. We argue a) that these effects reflect the initial activation and subsequent self-inhibition of the primed response, and the corresponding inhibition and subsequent disinhibition of the non-primed response, and b) that they are generated at dissociable local (within response channels) and global (between channels) levels of motor control. In two experiments, global-level priming effects were modulated by changing the number of response alternatives, whereas local-level effects remained unaffected. This suggests that low-level motor control mechanisms can be successfully decomposed into separable sub-components, operating at different levels within the motor system.