The forest, the trees, or both? Hierarchy and interactions between gist and object processing during perception of real-world scenes

The global-to-local theories of perception assume that the gist of a scene is computed early and automatically, whereas recognition of objects occurs at a later processing stage, requires attentional resources, and is primed by the representation of gist. To test these theoretical predictions, we investigated the processing hierarchy of gist- and object-recognition and their interaction in two experiments (total N = 60). Backward-masked images of real-world scenes were presented for a range of brief durations - between 8 ms and 100 ms, and participants performed either an object or a background classification task, in separate blocks. We report three main findings. First, scenes' backgrounds were generally classified more accurately than foreground objects, but recognition of objects was boosted to the same level as backgrounds by cueing spatial attention to the exact object's location. Second, backgrounds influence objects' recognition, as objects presented within semantically incongruent backgrounds were classified less accurately. Third, objects influence background categorization, as backgrounds comprising incongruent objects were also classified less accurately. Therefore, the first two findings support the global-to-local theories, implying that gists are indeed more readily perceived than objects, probably at an earlier stage. Yet the latter finding that objects also influence gist recognition suggests a more parallel and interactive view of both processes than previously assumed.