The role of direct parameter specification and attentional capture in near-threshold priming of motor reactions

The priming of motor responses can be induced by preceding visual stimuli that have been made invisible by metacontrast masking ('primes'). According to the concept of direct parameter specification( DPS;Neumann,1990),strong similarity between prime and target results in the processing operations that are to be applied to the target being also induced by the prime. As targets have to be attended to, this also implies that attention is captured by the location of a prime, thereby facilitating motor priming effects. This hypothetical effect may be viewed as a form of top-down attentional capture. In some subliminal priming experiments (e.g. Jaśkowski, Skalska, & Verleger, 2003), however, attentional capture may have been unrelated to target identity, as stimuli with unique features (singletons) are known to induce bottom-up attentional capture. Three experiments were performed that largely confirmed the view that the results of these earlier experiments were due to top-down attentional capture, in line with DPS. However, the priming effect was also evoked by a singleton irrelevant to the participants' task, although this effect was weaker than in case of strong similarity between prime and target. Priming effects remained when singletons were absent from one side of the visual field, suggesting that the presence of singletons is not a requirement for the observation of motor priming effects.