Abstract
Recent work studying the temporal dynamics of visual scene processing (Harel et al., 2016) has found that global scene properties (GSPs) modulate the amplitude of early event-related potentials (ERPs). It is still not clear to what extent the processing of these GSPs is influenced by their behavioral relevance and the goals of the observer. To address this question, we investigated how behavioral relevance, operationalized by task context, impacts the electrophysiological responses to GSPs. Across two experiments we recorded ERPs while participants viewed images of real-world scenes, varying along two GSPs (naturalness and spatial expanse). In Experiment 1, little attention to scene content was required because participants viewed the scenes while performing an orthogonal task. In Experiment 2, participants saw the same scenes but now had to actively categorize them, based either on their naturalness or spatial expense. We found that task context had little impact on early ERP responses to the naturalness and spatial expanse of the scenes: P1, N1, and P2 could distinguish between open and closed scenes and between manmade and natural scenes across both experiments. The specific effects of naturalness and spatial expanse on the ERP components were largely unaffected by their relevance for the task. A task effect was found but was manifest across all scene dimensions, indicating a general effect rather than an interaction between task context and GSPs. Together, these findings suggest that the extraction of global scene information reflected in the early ERP components is rapid and little influenced by top-down observer-based goals.