Perceiving Multiple Scene Events at the Grand Time Scale of Seconds

Scene perception research has focused on brief events at the time scale of milliseconds. Humans, however, are more practiced perceiving events lasting seconds. How important is attentional set at this more natural time scale? Extending previous work, we used relatively simple displays with 4 simultaneously active objects and 2 event types. The events were human figures animated over 2.4 sec lifetimes. In the motion task, walking figures swung their arms; targets also clapped once. In the color task, the figures were static and shirt color changed slightly, or more for targets. During each 24 sec trial, there were 36 animated tokens and 4 of them became targets (requiring responses). Perceptual efficiency was measured in terms of sensitivity. To learn about attentional set, we varied the events – the figures varied in orientation or task. In Experiment 1, tokens varied in orientation (2 orientations differing by 90 deg rotation). Relative to single-orientation conditions, perceptual efficiency was reduced by varying orientation, indicating that object orientation is part of the attentional set. In Experiment 2, a single orientation was used but the tokens varied in task (color or motion). Relative to single-task conditions, perceptual efficiency was reduced by task variation, confirming that task is part of the attentional set. In Experiment 3, we compared single-orientation, single-task conditions to mixtures of orientation and task. The reduction in perceptual efficiency due to orientation+task variation was greater than the sum of costs of varying orientation or task only. This suggests that task and spatial orientation are both integral to attentional set. The results provide further evidence that attentional set, including spatial properties of set, is important for scene perception at natural time scales, even when the number of objects was within object-attention limits