Abstract
Visual search—looking for targets among distractors—underlies many critical professions (e.g., aviation security, radiology), making it important to understand the mechanisms that govern performance. Previous research has demonstrated that repeating features benefit search performance, however this has not been thoroughly studied through the lens of associative binding, wherein co-occurring information links into singular memory representations that strengthen encoding. Complex visual search tasks, arguably, provide a highly sensitive window into associative binding mechanisms that can potentially inform an open debate about whether associative binding operates over task-irrelevant information (e.g., backgrounds, distractors). The “associative blocking” account suggests only task-relevant and 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 unitary mechanism wherein all information, regardless of task relevance, is processed and available for binding. Performance was assessed across consecutive trials, wherein both task-relevant and task-irrelevant features co-occurred. Data were drawn from a massive (>3.8B trials, >15.5M participants) visual search dataset (Airport Scanner; Kedlin Co.). In line with the prediction that associative binding can operate over task-irrelevant features in search, 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 a repeated target or repeated bag individually. The results suggest that binding may be a natural consequence of visual processing that is strengthened by, but not reliant on, relevance. This research may also provide insights into existing debates surrounding associative blocking; suggesting that attentional selection is nonessential for associative binding. In sum, these results suggest that implicit learning, even of associations, can profoundly shape behavior without conscious awareness or attention.