Masked singleton effects.

In the present study, we tested whether visual singletons remaining outside awareness are processed. Singletons differ by at least one feature from their more homogeneous neighbors. Here, we used backward masking to prevent awareness of shape singleton primes (Experiments 1-4) or color singleton primes (Experiment 5). Masked singleton primes nonetheless produced a congruence effect: Congruent singletons indicating the location of subsequent visible targets facilitated responses, in comparison with incongruent singletons at positions away from the targets. This congruence effect was found with singletons defined by feature presence or feature absence. It was at least partly due to attentional capture by singletons remaining outside of the participants' awareness. Results are discussed in light of theories pertaining to singleton effects and masked-priming effects.