1) A quantitative formulation stating that the relative rates of different responses tend to equal the relative reinforcement rates they produce. The generalized matching law summarizes this relation in an equation in which relative response rate equals a constant multiplied by the relative reinforcement rate raised to a power. The constant takes into account units of measurement and includes bias (e.g., one response might call for a larger constant than another that is more effortful); the performance is described as under matching when the exponent (the power to which the function is raised) is less than 1 and overmatching when it is greater than 1.

2) The relative rate of responding on two concurrent schedules of reinforcement equals the relative rate of reinforcement on those two schedules.

3) A description of a phenomenon according to which organisms tend proportionally to match their responses during choice situations to the rates of reinforcement for each choice (i.e., if a behavior is reinforced about 60% of the time in one situation and 40% in another, that behavior tends to occur about 60% of the time in the first situation, and 40% in the second).

4) When two or more concurrent-interval schedules are available, relative rate of response matches (or equals) relative rate of reinforcement.