This invention provides methods, system, and apparatus for assessing and/or diagnosing a neurobehavioural disorder in a subject. The methods, systems, and apparatus include the subject freely observing a visual scene, without having to carry out a task or follow specific instructions. In one embodiment, a computational model is used to select one or more feature in a visual scene and generate a spatial map having first map values that are predictive of eye movement end points of a hypothetical observer relative to the one or more feature. A subject's eye movements are recorded while the subject freely observes the visual scene, and a difference between second map values that correspond to the subject's eye movement endpoints and a set of map values selected randomly from the first map values is quantified, wherein the difference is indicative of a neurobehavioural disorder in the subject. Neurobehavioural disorders such as Parkinson's disease, Alzheimer's disease, Huntington's disease, fetal alcohol spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, autism, Tourette syndrome, and progressive supranuclear palsy may be assessed and/or diagnosed.