The principal components of response strength

As Skinner (1938) described it, response strength is the "state of the refl ex with respect to all its static properties" (p. 15), which include respon se rate, latency, probability, and persistence. The relations of those meas ures to one another was analyzed by probabilistically reinforcing, satiatin g, and extinguishing pigeons' key pecking in a trials paradigm. Reinforceme nt was scheduled according to variable-interval, variable-ratio, and fixed- interval contingencies. Principal components analysis permitted description in terms of a single latent variable, strength, and this was validated wit h confirmatory factor analyses. Overall response rate was an excellent pred ictor of this state variable.