Abstract
A persisting question in attention research is how much processing unattended items receive. Priming studies have shown that semantically related items can improve reaction times to a subsequent target without awareness of the prime, while picture-word interference studies have shown that semantically related items can interfere with responding. In the current study we employed the method of Rees et al. (1999) using superimposed pictures and words (Experiment 1) or superimposed large and small pictures (Experiment 2) to examine the effect of semantic congruency (e.g., picture of a ball and the word “ball”) in an unattended channel on reaction times to detect a repeated item in an attended channel. This method additionally allowed us to examine whether repetition redundancy and repetition blindness can occur in the unattended channel. Observers were asked to attend either to one channel of an RSVP stream (pictures or words; large or small pictures) and to ignore the information in the other channel. Task structure and timing were chosen to make attending to the non-target stream highly disadvantageous for doing the primary task well. We show that semantic congruency from the unattended channel exerts differential effects on reaction times to the repeated item depending on the temporal proximity between the two items and on which type of information is in the attended channel (words or pictures). This indicates that under some circumstances unattended items are processed to a level at which they can influence behavior.