Abstract
Expectancy to a spatial location facilitates processing of a target on the expected location. We studied whether and to what extent the sequential expectation of more than one locations would facilitates the processing at expected locations. Observers performed a color-discrimination task for sequentially presented targets. Four targets were presented sequentially on one of eight iso-eccentric placeholders. In 80% of trials (regular trials), the target location was regularly shifted in the clockwise direction for each target presentation, which encouraged observers to form spatial expectation not only to the second target location but also to the subsequent (third and fourth) locations. In 20% of trials (irregular trials), the second target appeared at random (except for the clockwise next) locations. The third and fourth targets appeared in the clockwise locations of the second target. Hence, the second target occasionally appeared on the expected third and fourth locations. We examined whether the processing of?the second target would be facilitated compared to that of the first target when the second target accidentally appeared on the expected third or fourth locations in irregular trials. Reaction times were shorter for the second target in regular trials. This held true in irregular trials but only when the second target was presented on the expected third location. A control experiment showed that, when the two-target sequence was used (no expectation of the third or fourth location), the location clockwise to the expected second target did not exhibited facilitation, excluding the possibility of a general enhancement at clockwise locations of the first target. These results showed the extent of attentional facilitation based on sequential expectancy to target locations. Attention can facilitate visual processing on locations of up to at least two future events.