A Taxonomy of Inverse Priming Based on Stimulus Characteristics

Abstract

One intriguing question in cognitive neuroscience is whether subliminal stimuli can affect overt behavior. A straightforward experimental approach to demonstrate effects of subliminal stimuli is the response priming paradigm. In response priming, a masked prime stimulus facililitates processing of targets which require the same response (congruent condition) as opposed to targets requiring an alternative response (incongruent condition). When prime visibility is reduced by an additional masking stimulus following the prime but preceding the target, priming effects are reversed. Then, performance costs are observed in the congruent condition and benefits in the incongruent condition. Various explanations for this couterintutive phenomenon have been proposed including perceptual, central and motor accounts. Empirical findings regarding the locus of inverse priming are divergent.Five research projects have been performed in order to clarify the mechanism underlying the inverse priming effect. Psychophysical and physiological evidence support the view that inverse priming is generated in different ways according to the characteristics of the stimuli involved. When primes and targets are compatible to the responses assigned to them, like double arrows which require corresponding left-hand and right-hand responses, inverse priming seems to originate from the motor system. Probably, subliminal primes automatically activate the corresponding response which becomes inhibited due to the presentation of the masking stimulus finally leading to a bias for the incongruent response. In contrast, inverse priming with response non-compatible stimuli, like squares and diamonds, is supposed to be entirely generated at perceptual levels of processing. Furthermore, inverse priming with such stimuli seems to be limited to the use of masks which comprise task-relevant features. With such relevant masks, inverse priming presumably results from a perceptual interaction of primes and masks rendering prime-incongruent elements in the mask more salient which in turn facilitates perceptual processing of incongruent targets. With irrelevant masks, small but reliable effects have only been found in a non-motor priming task indicating that a further distinct mechanism might produce inverse priming.Thus, inverse priming illustrates that a single observable phenomenon can be produced by various different mechanisms according to the stimuli employed. On a more abstract level, results suggest that the influence of subliminal stimuli goes beyond the simple activation of motor responses. Complex control processes seem to be triggered by subliminal stimuli which remain unconsicous.