"...antecedent stimuli that increase the probability of a desired response" (Piazza, & Roane, 2014, p. 256).

"...transfer stimulus control from therapist delivered prompts to stimuli in the natural environment that should evoke appropriate responses" (Walker, 2008 cited in Fisher, Piazza, & Roane, 2014, p. 412).

"...those in which some property of the criterion stimulus is altered, or other stimuli are added to or removed from the criterion stimulus" (Etzel & LeBlanc, 1979 cited in Fisher, Piazza, & Roane, 2014, p. 256).

"...addition of some behavior on the part of an instructor to evoke the desired learner behavior" (Fisher, Piazza, & Roane, 2014, p. 256).

"A sequence of responses in which each response produces a stimulus change that functions as conditioned reinforcement for that response and as a discriminative stimulus for the next response in the chain" (Cooper et al, 2007, p. 691).

"Reinforcement for the last response in a chain maintains the reinforcing effectiveness of the stimulus changes produced by all previous responses in the chain" (Cooper, Heron, & Heward, 2007, p. 691).

"...behaviors that have discrete beginning and ending points, require minimal displacement of the organism in time and space, can be emitted at nearly any time, do not require much time for completion, and can be emitted over a wide range of response rates" (Cooper, Heron, & Heward, 2007, p. 696).

Rate of responding is typically used to measure behavior considered to be free operant. Rate of responding is typically used because it uses count per unit of time. (i.e., a person can type 50 words per minute). However, rate of responding is not typically used to measure behavior that occurs within discrete trials. These responses can occur only within limited or restricted situations.

"Any operant whose response rate is controlled by a given opportunity to emit the response. Each discrete response occurs when an opportunity to respond exists" (Cooper et al., 2007, p. 694).