Abstract
In cognitive experiments, eye fixation data are often used to determine what information about a stimulus is being analyzed for a given task and thus what underlying processes are occurring in the brain. Perceptual expertise may be based on knowledge about the location of distinguishing features on a set of stimuli (Biederman & Shiffrar, 1987) and we would predict a change in eye fixation patterns toward the distinguishing features as expertise is acquired. In this study we investigated the relationship between eye fixations and the visual information needed to complete a task as participants developed expertise. We used novel real-world stimuli, photographs of whale tails, that were modified to control the location of the critical information. Participants were asked to discriminate the identity of the whales based on the tail features in a forced-choice paradigm and received feedback after each trial. One group of participants completed the experiment with a single informative location on the whale tail, and a second group with two critical locations, where the conjunction of features determined identity. Dependent measures collected included accuracy, reaction time, and eye tracking. As expected, participants’ reaction time decreased as accuracy increased. Additionally, fixations changed over time, with an increased likelihood to fixate at the diagnostic locations. For whale tails with a single informative location, fixations were tightly constrained to the diagnostic location. In the two-location condition, we observed two patterns emerge, such that one group of participants fixated on each relevant location in a discrete, sequential fashion, while the other developed a distinct pattern of fixating a single diagnostic location on the whale tail even though both contained information necessary for task performance. These latter results suggest the development of holistic processing during tasks with distributed information. Perceptual expertise may induce a dissociation between fixation patterns and task relevant information.
Acknowledgement: Intramural Program of NIMH