Abstract
Purpose: Human infants start to learn about and interact with their environment during the first postnatal months. Immaturities in their motor responses and spatial vision constrain their visual behavior during this period of rapid development. The goal of this study was to determine how these immaturities interact to define the visual behavior of developing infants in a naturalistic setting. Methods: Participants aged 2-12 months wore head-mounted scene and binocular eye-tracking cameras (a modified PupilLabs Core system) while engaging in naturalistic behavior in a home-like environment in the lab. Calibrated eye movements were corrected for optical distortion in the head-camera images and then compiled into gaze position distributions over recordings of at least 4 minutes. These distributions were then fit with a cumulative density function over eccentricity from primary gaze. Results: Videos from infants in age groups of 2-3, 5-6, 8-9 and 11-12 months were analyzed. 43% of infants provided sufficient quality videos lasting at least 4 minutes. The 0.8 point on the individual cumulative density functions from median gaze position ranged from 15-40 degrees across infants, resulting in a correlation of 0.77 (p=0.004) with age group. Conclusions: The youngest infants have limited head and trunk control and exhibited the most restricted range of gaze position, suggesting that they are not compensating for their limited mobility by shifting their gaze on the timescale of these recordings. This likely leads to less active sampling of visual information, slower rates of change in the input, and a tight link between head- and eye-centered frames of reference for vision. Maturation of motor responses and vision appear to result in a greater range of ocular motor exploration over the first postnatal months.