Systems, devices, and methods are described for assessing the risk of developmental, cognitive, social, or mental abilities or disabilities in very young patients (e.g., in the first 2-6 months of life). Generally, the decline in visual fixation of a subject over time with respect to certain dynamic stimuli provides a marker of possible abilities or disabilities (such as ASD). The visual fixation of the subject is identified, monitored, and tracked over time through repeated eye tracking sessions, and data relating to the visual fixation is then analyzed to determine a possible increased risk certain conditions in the subject. A change in visual fixation as compared to similar visual fixation data of typically-developing subjects or to a subject's own, prior visual fixation data provides an indication of a developmental, cognitive, or mental ability or disability.
