Abstract
Increasing attention to one task typically interferes with performance on another. However, responding to targets in a continuous task paradoxically enhances memory for background scenes. This “attentional boost effect” reflects a transient increase in attention when target detection triggers a temporal orienting response. To date, researchers have primarily investigated the attentional boost effect under exogenous temporal orienting conditions, in which the targets are temporally unpredictable. Yet humans can endogenously orient to predictable moments as well. To understand how endogenous and exogenous temporal orienting affect concurrent task processing, we explored the interaction between temporal predictability and the attentional boost effect. Participants memorized a stream of scenes presented at 1s/scene, while concurrently monitoring a stream of digits for a target digit––the number 0 in Experiment 1, and 0 in a specific color (green or red) in Experiment 2. In half of the blocks, the appearance of the 0 was predicted by the preceding sequence 3, 2, 1. In the other half of the blocks, 0 could appear at any moment. Results from the unpredictable blocks replicated previous findings: participants showed better memory for scenes coinciding with the target 0 than with nontarget digits, and this boost was confined to 0 in the specified target color. When 0 was temporally predictable, participants still showed an attentional boost effect for scenes coinciding with the 0, and in contrast to predictable blocks, this effect extended to 0 in the nontarget color. Memory was not better for scenes coinciding with predictive digits. This suggests that regardless of whether an expected target appears, the boost from endogenous temporal orienting occurs at the moment to which one orients, rather than the moment of the predictive cue. This study provides insights into temporal orienting mechanisms, demonstrating that endogenous orienting, like exogenous orienting, triggers a transient boost in attentional resources.