How Does the Purpose of Inspection Influence the Potency of Visual Salience in Scene Perception?

Abstract

Salience-map models have been taken to suggest that the locations of eye fixations are determined by the extent of the low-level discontinuities in an image. While such models have found some support, an increasing emphasis on the task viewers are performing implies that these models must combine with cognitive demands to describe how the eyes are guided efficiently. An experiment is reported in which eye movements to objects in photographs were examined while viewers performed a memory-encoding task or one of two search tasks. The objects depicted in the scenes had known salience ranks according to a popular model. Participants fixated higher-salience objects sooner and more often than lower-salience objects, but only when memorising scenes. This difference shows that salience-map models provide useful predictions even in complex scenes and late in viewing. However, salience had no effects when searching for a target defined by category or exemplar. The results suggest that salience maps are not used to guide the eyes in these tasks, that cognitive override by task demands can be total, and that modelling top-down search is important but may not be easily accomplished within a salience-map framework.