The briefest of glances:
the time course of natural scene understanding.
Greene, M.R., & Oliva, A. (in press, 2009). Psychological Science.

What is available from a brief glance at a novel scene?  While previous efforts to answer this question have focused on scene categorization or object detection, real-world scenes contain a wealth of information whose perceptual availability has yet to be explored.  Here we used image exposure thresholds to compare several basic-level category and global scene classification tasks. Thresholds on all tasks were remarkably short: observers achieved 75% correct performances with presentations ranging from 19ms to 67ms, reaching maximum performances after only 100 ms.  Global property tasks had significantly shorter thresholds than basic-level tasks suggesting that there exists a time during early visual processing where a scene may be classified as a large space or navigable, but not yet as a mountain or lake. Comparing the relative availability of visual information reveals bottlenecks in the accumulation of meaning. Understanding these bottlenecks provides critical insight into the computations underlying rapid visual understanding.

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