In its early form, behavior analysis dealt with three key variables, namely discriminative stimulus, response, and reinforcing stimulus. These three [Page 528]categories did not cover all experimental variables. Some procedures were undertaken that were not incorporated into the functional analysis. For example, experimental animals were routinely deprived of food, thus increasing the likelihood that food pellets would be effective reinforcers. However, deprivation was not given a central place in the functional analysis. When concepts from the experimental analysis of behavior were applied to human behavior in natural settings, some researchers saw a need for an additional type of variable. Two approaches were adopted.

One was to take over the label “setting factors or events” from interbehavioral psychology. This was ...