Vision using routines: A functional account of vision

This paper presents the case for a functional account of vision. A variety of studies have consistently revealed "change blindness" or insensitivity t o changes in the visual scene during an eye movement. These studies indicat e that only a small part of the information in the scene is represented in the brain from moment to moment. It is still unclear, however, exactly what is included in visual representations. This paper reviews experiments usin g an extended visuo-motor task, showing that display changes affect perform ance differently depending on the observer's place in the task. These effec ts are revealed by increases in fixation duration following a change. Diffe rent task-dependent increases suggest that the visual system represents onl y the information that is necessary for the immediate visual task. This all ows a principled exploration of the stimulus properties that are included i n the internal visual representation. The task specificity also has a more general implication that vision should be conceptualized as an active proce ss executing special purpose "routines" that compute only the currently nec essary information. Evidence for this view and its implications for visual representations are discussed. Comparison of the change blindness phenomeno n and fixation durations shows that conscious report does not reveal the ex tent of the representations computed by the routines.