Performance and its measurement.

Performance involves numerous sub-functions, and cannot be treated as a unit. Several attempts have been made to separate functions impaired by different classes of drug: for example, high (monitoring) vs lower (performing) levels of function, early (perceptual) vs later (motor) functions, and strategic vs executive functions. The practical implications are that one cannot predict effects of a drug from a single performance test. One must either simulate the practical situation exactly, or use a battery of analytical tests to form a profile of effects. The latter is the policy urged in this paper.