Systems, devices, and methods are described for the assessment, screening, monitoring, or diagnosis of developmental or cognitive conditions, including autism spectrum disorders (ASD) by analysis of eye tracking data generated from feedback received as a result of display of specific predetermined visual stimuli to a subject or patient. Subsequent to a calibration phase, a testing procedure is performed by presenting predetermined stimuli (e.g., videos) to a subject via a display device. Eye tracking data (from the subject moving his or her eyes in response to predetermined movies or other visual stimuli) are collected. During the data collection period, the system periodically presents targets to reflexively elicit the subject's gaze. These data are used to later verify accuracy. Analysis of the subject's viewing patterns during these stimuli is used for the assessment, screening, monitoring, or diagnosis of developmental or cognitive conditions such as ASD.