Two routes to a target: Visual priming for direct and indirect attentional sets.

To find an item of interest among candidate objects we are directed by attentional sets that reflect our expectations and intentions and may also vary by whether items should be attended or ignored. We investigated how different attentional sets influence target search and the effect of prior experience on these attentional sets. Our participants had to identify a target object given a set of objects that either contained the target itself (direct attentional set) or contained only cues that defined the target by exclusion (indirect attentional set). We found that response times were significantly slower for indirect attentional sets and when sets were mixed within blocks. To analyze the impact of attentional sets on priming, we fitted behavioral time series using multiple dynamic ideal observer models based on a first-order memory mechanism with three consecutive stages: set identification (direct vs. indirect), target identification (based on set cues), and response. The different models involved different assumptions about each stage, and we compared them via information criterion to identify mechanisms that consistently lead to good expected out-of-sample performance. We found strong repetition priming when both set and target were repeated. For direct attentional set, repetition priming was consistent with a first-order memory mechanism that tracks objects and colors likely connected to feature-specific neural mechanisms and frontoparietal attention network. In contrast, the processing of indirect attentional sets relies on qualitatively different mechanisms and search strategies than conventional visual search, likely related to neural networks involved in task switching and generation of attentional set.