Early and late selection in unconscious information processing.

In four experiments, we investigated whether masked stimuli in priming experiments are subjected to early or to late selection. In Experiment 1, participants classified four target-pictures as being small or large. In line with early selection accounts, prime-pictures with a different perceptual appearance as the experienced targets did not elicit congruency effect. In Experiment 2, 40 targets all depicting animals were presented. Results were in line with late selections assumptions because novel animal primes but not novel primes from different semantic categories yielded congruency effects. In Experiment 3, the targets were chosen such that there is a second semantic feature that covaried with the required response. Here, novel primes picturing small animals did not influence target responses with regard to the instructed size classification, but with regard to their affiliation to the category animal. In Experiment 4, small and large pictures from two categories were presented. Category match did not influence priming, ruling out that feature overlap contaminated the former results. The results indicate that participants' prestimulus expectations determine in which stage in the processing-stream masked stimuli are selected.