What is stimulus control in ABA?
Stimulus control is the state in which a behavior occurs reliably in the presence of a particular cue and not otherwise, produced by a history of the behavior being reinforced in that cue's presence.
Answering a phone only when it rings, stopping at red and going at green, lowering your voice in a library - each is behavior under stimulus control. The cue doesn't force the behavior; it signals that the behavior will pay off now, because that has been the history.
Teaching in ABA is largely the engineering of stimulus control. In discrete trial teaching, the instruction 'touch nose' becomes the discriminative stimulus for a specific response through differential reinforcement - reinforced in its presence, not otherwise. Discrimination training sharpens the control: responding to the target cue is reinforced, responding to similar-but-wrong cues is not, until the learner reliably tells them apart.
Prompts are temporary stimulus control, and prompt fading is the transfer of that control to where it belongs. A learner who says 'ball' only after hearing the model has the behavior under echoic control; fading the model until the ball alone occasions the word is called transfer of stimulus control - the mechanic underneath most skill acquisition.
Problems of stimulus control explain familiar clinical patterns. Prompt dependence is control resting on the prompt instead of the natural cue. Rote responding is control that is too narrow - the learner answers correctly only for one therapist, one card, one phrasing. Generalization work is deliberately broadening control across people, materials, and settings.
Reading acquisition data through this lens is what separates 'it looks mastered' from mastery: independence means the natural cue controls the response, and the fading steps recorded in each session are the evidence trail of that transfer happening.