1) A complex behaviour consisting of two or more response segments that occur in a definite order. A chain can be homogeneous or heterogeneous. Homogeneous chains consist of responses that are similar to one another, as in lifting or throwing. Heterogeneous chains consist of responses that differ from one another, as in playing football or assembling a barbecue.

2) A sequence of discriminated operants such that responses during one stimulus are followed by other stimuli that reinforce those responses and set the occasion for subsequent ones. Not all temporally integrated sequences are maintained through chaining; those that are not must be distinguished from those that are. Parts of a chain are variously called components, links, or members. Procedures for creating chains often start with responses at the ends of the sequence, closest to the reinforcer, and then work back (backward chaining); starting from the other end (forward chaining) is more difficult, because early responses may extinguish while later ones are being shaped. Chains with topographically sin-dlar responses are homogeneous (e.g., a pigeon's pecks in a chained schedule); those with topographically dissimilar responses are heterogeneous (e.g., a sequence consisting of alley-running, lever-pressing, and moving to a feeder).

3) A chain consists of two or more performances linked by common stimuli. One performance produces the conditions which make the next possible. The stimulus linking the two performances serves both as a conditioned reinforcer maintaining the topography and frequency of the first performance, and as a stimulus setting the occasion for the second.

4) The most commonly used term for "stimulus/response chain."