Arousal, temporal and spatial uncertainty and drug effects.

1. Due to the multiplicity of a drugs pharmacological action a precise prediction of its behavioural effects is not possible. 2. A heuristic classification of drug effects on man should emphasize similarities and differences between different pharmacological classes. 3. A comparison of several drugs acting on the catecholamine system suggests they influence stimulus selection by affecting the organism's preparation. 4. Sedative - hypnotics, including alcohol, appear to act on different mechanisms, slowing responding. 5. The action of these classes of drugs on memory also appeared to be dissimilar.