What the experimenter's prime tells the observer's brain

The presentation of a stimulus below the threshold of conscious awareness can exert an influence on the processing of a subsequent target. One such consequence of briefly presented "primes" is seen in the negative compatibility effect. The response time (RT) to determine the left-right orientation of an arrow (i.e., the target) is relatively slow if a prime is also an arrow whose direction corresponds to that of the target. When the direction of the arrow is opposite that of the prime, RTs are relatively fast. In four experiments, we examined whether the prime shifts attention from the location of the subsequent target and whether this attention shift influences target processing. Results showed that the prime does indeed move attention. The consequence of this attention movement is that the representation of direction is affected. Specifically, RTs to process an arrow are shorter if the arrow's direction is compatible with the last shift of attention. Furthermore, this interference occurs at a conceptual level concerning the representation of left and right rather than at the motor planning level. We argue that a shift in attention brought about by the prime can create a negative compatibility-like effect.