Automatic selection of eye tracking variables in visual categorization for adults and infants

Visual categorization and learning of visual categories exhibit early onset, however the underlying mechanisms of early categorization are not well understood. The main limiting factor for examining these mechanisms is the limited duration of infant cooperation (10-15 minutes), which leaves little room for multiple test trials. With its tight link to visual attention, eye tracking is a promising method for getting access to the mechanisms of category learning. But how should researchers decide which aspects of the rich eye tracking data to focus on? To date, eye tracking variables are generally handpicked, often resulting in biases of the eye tracking data. Here, we propose an automated method for selecting eye tracking variables based on their usefulness to discriminate learners from non-learners of visual categories. We presented infants and adults with a category learning task and tracked their eye movements. We then extracted an over-complete set of eye tracking variables encompassing durations, probabilities, latencies, and the order of fixations and saccadic eye movements. We applied the statistical technique of ANOVA ranking to identifying those variables among this large set that covaried with the learner/nonlearner label. We were able to identify learners and nonlearners above chance level using linear SVM and the top eye tracking variables.