A method and apparatus for quantifying differences in human sensorimotor performance useful for diagnosing, assessing, and/or detecting brain injury and/or a neurological disorder, or identifying exceptional performance in a subject. In a task a subject's limb movement is restricted to a limited workspace and an object moves towards the limb. The objective of the task is for the subject to contact the object with the limb within a set time period. During the task a perturbation directed to the object and/or limb, or other feature of the environment, may occur on some trials, requiring a rapid motor correction in order to contact the object, or the subject may receive an alternative instruction on whether to interact with the object. Position data and/or motion data and/or kinetic data of the limb or portions thereof with respect to a presented object are obtained, and a data set is acquired for a plurality of trials. The acquired data set provides information about brain injury and/or a neurological disorder in the subject or exceptional capabilities of the subject.