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Rapid Natural Scene Categorization without Attention
Fei Fei Li, Rufin VanRullen, Christof Koch, Pietro Perona

Abstract. While attention is not necessary for some detection tasks on simple synthetic stimuli, without it we are “blind” even to major aspects of a natural complex scene. It would thus appear that only visual tasks that have an explanation in the early stages of the visual system may be carried out without attention. We report on a complex visual task that requires no attention. Our subjects can rapidly detect animals in briefly presented natural scenes while simultaneously performing another visual task that demands full attention. We conclude that attention may not be necessary for some visual tasks that are associated with ‘high level’ cortical areas.

Motivation. Psychologists have long known that certain visual search tasks do not require attention. A hallmark of inattentive visual is that it is achieved in a parallel fashion: an inattentive task may be carried out simultaneously with other visual tasks; target detection does not become more difficult when the number of distractors is increased. For example, the following three panels are three examples of inattentive tasks taken from Braun and colleagues’ study in 1998.

However, none of the known inattentive tasks approaches the sophistication of everyday vision where complex scenes must be scrutinized in order to assess high level properties such as presentation of danger or the structure of the social interaction.

Main Results. An attentionally demanding letter discrimination task is presented at the center of the visual field. In the peripheral natural scene categorization task, an image is presented peripherally for a very brief time (27msec). Under the dual task condition, subjects are required to perform both tasks concurrently.

As illustrated by the following figure, our results show that there is little or no attentional cost for subjects to perform the natural scene categorization task when attention is withdrawn by the central letter discrimination task. Here we show a normalized average performance by all subjects, each represented by one dot from each color. Red dot indicates performance collected from trained images. Blue dot indicates performance collected from completely novel images. The horizontal axis represents performance of the central task (attentionally demanding). The vertical axis represents performance of the peripheral task (natural scene categorization). For each subject, his/her single task performance on both the peripheral task and the central task are independently normalized to 100%. Our goal is to compare the dual task performances, represented by red and blue dots. Clustering of the dots at the (100,100) corner indicates that subjects can simultaneously perform both the central letter task as well as the peripheral categorization task.

Conclusion. We reported a study in which withdrawing attention entails little or no cost to the performance of a complex visual task, namely the natural scene categorization task. We also conducted a series of control experiments that compared this result with performing seemingly simpler, synthetic stimuli visual tasks. Contrary to our intuition, natural scene categorization appears to entail the least attentional demand. These results lend great motivation to future studies of attentional as well as recognition models of the human visual system.

Reference
F.F. Li, R. VanRullen, C. Koch and P. Perona. “Rapid natural scene categorization in the near absence of attention.” Proc Natl Acad Sci USA, 99(14), 9596-9601.