Abstract
The hallmark of endogenous attention is that it is under voluntary control. However, it is well known that stimuli that are not consciously perceived can nevertheless prime perceptual, motor, and even semantic processing, suggesting that such primes can deeply affect information processing. Can subliminal primes therefore also influence endogenous control of attention? To address this issue, we devised a dual-task experiment in which a masked priming task (Vorberg et al., 2003) was embedded within an endogenous Posner cuing task. At trial onset, the prime, a non-predictive arrow pointing left or right, was briefly presented at fixation. Following a variable interval a larger arrow, serving as both an endogenous cue (80% validity) and a metacontrast mask for the prime, pointed to one of two peripheral locations where a subsequent target stimulus could appear after a variable delay. Subjects made a speeded manual response to target presentation and an unspeeded response to the prime identity (left vs right arrow). Subjects showed typical cue validity effects, with quicker target detection at cued relative to uncued locations. Prime validity effects (the prime's ability to orient attention independent of cue orientation) and prime-cue congruency effects (the influence of prime orientation on the cue in the orienting task) were only present when subjects were aware of the prime. In a second experiment, the two tasks were performed in separate sessions. Similar results to the first experiment were obtained when the prime identity task was performed before the orienting task, but no prime validity or congruency effects were detected with the reversed task order even when the prime was consciously accessible, suggesting that the prime only affects the cuing of attention when it has acquired task relevance. Taken together, these results indicate that only primes that reach awareness can control endogenous orienting of attention.
Supported by a National Institute of Mental Health grant to R.M.