Abstract
Visual search—looking for targets among distractors—underlies many critical professions (e.g., aviation security, radiology, military operations), making it important to understand the mechanisms that govern performance. Feature repetition across trials benefits subsequent search performance, however this has not been thoroughly studied through the lens of associative learning, wherein relationships between temporally or spatially co-occurring stimuli are repeated and learned across consecutive search trials. Complex visual search tasks provide a window into associative learning that can potentially inform a debate about whether the learning operates over task-irrelevant information (e.g., backgrounds, distractors). The “associative blocking” account suggests only task-relevant, highly salient features bind with targets. Yet recent findings of trial sequence effects in search suggest that even task-irrelevant information impacts subsequent performance. Accordingly, the current study hypothesized that search performance is influenced by a mechanism of indiscriminate implicit learning wherein all information, regardless of task-relevance, is processed and available for learning. Performance was assessed for task-relevant and task-irrelevant features repeating both together and independently across consecutive trials pairs. Data were drawn from a massive (>3.8B trials, >15.5M participants) visual search dataset (Airport Scanner; Kedlin Co.). Contrary to the blocking account, the co-occurrence of both task-irrelevant and task-relevant information influenced performance. Specifically, the performance advantage for consecutive trials containing the same target and same irrelevant feature (e.g., bag-type) exceeded the summed benefit of each element repeating individually. Preliminary findings on relative Euclidean distance in the search arrays between the repeated targets provides possible evidence for an allocentric representation relative to the bag. The results suggest that learning may be a natural consequence of visual processing that is strengthened by, but not reliant on, relevance; suggesting that attentional selection may be unnecessary for associative learning. In sum, the current study supports that implicit learning, even of associations, could shape behavior without directed attention.