"...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).