A class of drug (including amphetamine), which has the effect of increasing the level of activity in a given situation.

Behaviour that is out of touch with conventional reality. (Adjective: psychotic.)

A consequence that is contingent upon a particular response and which reduces the frequency of exhibiting that response in the future. An example of a punishment is an electric shock.

Describes behaviour directed to obtaining a goal and guided by a representation of the goal.

The overall shape of a protein made up of two or more polypeptide chains.

Effect observed in investigations of short-term memory. Subjects are presented with a sequence of 15–30 unrelated words. Immediately after the last word, they are asked to recall as many words as they can in any order they wish. Performance on this task shows that the last few words are recalled extremely well – the recency effect.

The area of sensory surface which, when stimulated, changes the activity of a neuron in a sensory system.

A term with two very different meanings in neurobiology:

1. A sensory neuron or that part of one which is responsible for sensing information in the environment (e.g. light receptors in the eye).
2. Protein molecule embedded within a cell membrane which when occupied by a particular hormone, drug, or neurotransmitter initiates a change in cell function.

A return to drug taking after a period of abstinence.

Term referring to the observation that a plot of percentage survival against age for populations of modern Western societies is roughly rectangular in shape. This indicates that the average lifespan is approaching the maximum lifespan. The maximum lifespan is presumed to remain fairly constant.