Detecting early communication: using measures of movement-related potentials to illuminate human information processing.

In this paper we review evidence that suggests that the stimulus evaluation system can pass information to the response activation system before evaluation is completed ("early communication"). This evidence is derived from measures of the lateralized readiness potential, which have been related in previous research to the preparation for movement. Early communication is evident in conflict and congruence paradigms. In both paradigms, a single stimulus, or two different stimuli, deliver two aspects of information. In the conflict paradigm, the first aspect of information (derived from preliminary evaluation) primes the incorrect response, while the second primes the correct response. In the congruence paradigm, information derived from preliminary and complete evaluation is congruent. In both paradigms, lateralized readiness potential measures suggest that preliminary evaluation is able to prime the response system, although the overt motor response may not be released until evaluation is completed. This demonstration of early communication has both theoretical and practical implications. First, it does not support single-decision models of information processing. Second, it suggests that the lateralized readiness potential, a continuous, analog measure of the activity of the response system, can be used to make inferences about the nature of the evaluation process, and to localize the effects of various manipulations on the information processing system.