SAIL Room - 111 Levin Building
Psychological and Brain Sciences
University of California, Santa Barbara
Rapidly Looking at Faces: A Sensory Optimization Theory
When viewing a human face people first look towards the eyes. A prominent idea holds that these fixation patterns arise solely due to social norms. Here, I propose that this behavior can be explained as an adaptive brain strategy to learn eye movement plans that optimize the rapid extraction of visual information for evolutionary important perceptual tasks. I show that humans move their eyes to points of fixation that maximize perceptual performance determining the identity, gender, and emotional state of a face. These initial optimal points of fixation, which vary moderately across tasks, are correctly predicted by a foveated Bayesian ideal observer (FIO) that takes into account the task, integrates information optimally across the face but is constrained by the decrease in resolution and sensitivity from the fovea towards the visual periphery. A model that disregards the foveated nature of the visual system and makes eye movements either to the regions/features with the highest discriminative information or center of the face fails to predict the human fixations. The preferred points of initial fixation are similar across cultural groups (East Asians vs. Caucasians). However, there are individual differences. A majority of observers (~ 85 %) look just below the eyes and a minority (~15 %) closer to the tip of the nose and below. The systematic differences in initial points of fixation persist over time and also correspond to individual variations in the points of fixation that maximize perceptual performance. Finally, observers have difficulty changing their eye movement plans when confronted with unusual faces or simulated scotomas that make their over-practiced preferred points of fixation suboptimal. Together, these results illustrate how the brain optimizes initial eye movements to rapidly extract information from faces based on the statistical distribution of discriminatory information, general properties of the human visual system and individual specific neural characteristics. We propose that the ingrained nature of these highly practiced motor programs might suggest a domain specific neural representation of learned oculomotor plans.
The talk will begin at 12:00pm. A pizza lunch will be served at 11:45am.