Figure 1.
Stimuli and task. (a) Depiction of the stimuli used in the event-related runs. Each of the 7 objects pictured in the top row was superimposed on each of the 3 backgrounds in the second row. Two of the backgrounds implied a spatial layout (open and closed—space present), while one was matched for overall luminance but contained no spatial layout information (gradient—space absent). Images of the backgrounds only formed the object-absent condition (second row). The combined minimal scenes (third row) contained a single object and background, and every combination of the 2 was presented. This fully crossed design allowed the effect of background and object to be evaluated separately in the subsequent response magnitude and response pattern analyses. (b) Depiction of the sequence of events in a typical series of trials during the event-related runs. Each minimal scene was presented for 300 ms. To ensure participants maintained fixation, they performed a shape judgment task on the central fixation cross (see text for details). Intertrial intervals varied from 3700 to 12000 ms, and no response was required from the participants in this period. This variable delay was introduced to allow for efficient deconvolution of the responses.