The researchers aim to understand how babies and toddlers learn about their social surroundings and how this process differs in children with autism. Klin and Jones developed new eye-tracking technologies and data analysis strategies to track and quantify the gaze of babies and toddlers and identify the visual aspects of their environment that they are drawn to most strongly. The researchers propose to use these measures to study the development of social engagement and the derailment of this process in autism. This study will follow babies at a greater genetic risk for autism from birth to 6 months, and then every 3 months until they are 2 years old. More than 6,000 assessments are planned. Their measures will allow them to determine what subjects prefer to look at when viewing naturalistic and dynamic social scenes, follow how their preferential attention changes over time, assess the influence of voices and other sounds on social visual attention, and examine how stimulus properties (motion, contrast, and spatial resolution) of objects determine how much attention they attract. The researchers then plan to look for relationships between these data and the subjects' clinical information and social abilities. Their findings may identify very early manifestations of autism that could serve as diagnostic markers.