Stimulus Control Advanced Applied Behavior Analysis Presentation Based on Green (2001) and Chapter 17 of Cooper, Heron, and Heward (2007)

Background Contrary to popular myths about ABA, much of the basis for our current teaching technologies in stimulus control were already present in early pioneering work at U of Washington See early work of Bijou, Hart, Risley, Baer, etc. “generalization” and “antecedent control” were present a LONG time ago in comprehensive ABA programs

Antecedent Stimuli SD v. prompt Both are defined by FUNCTION, not whether the instructor labels them as such! “I used a prompt but it didn’t work.” 3-term contingency and relationship to term “trial” (I prefer “learning opportunity”!)

“Power” of Antecedent Stimuli Stimuli presented prior to a reinforced response will increase the likelihood of that response in the future. Period! If the stimulus could talk, it would be saying “Hey, remember that when I’m presented you should do X and that you’ll get a reward if you do? Remember that? Huh? Hey…Stop looking at that other thing!! Look at me!”

Stimulus Control Terms refers to both a process and a field of study In the former, it is the degree to which antecedent stimuli affect the likelihood of a response occurring In the latter, it is the study of the variables responsible for that process

Stimulus Control Stimulus Discrimination Stimulus Generalization

Stimulus Control Stimulus Discrimination Definition: Degree to which antecedent stimuli set the occasion for particular responses precise degree of stimulus control E.g., Man has beard and is Daddy; Man has beard and is Uncle Eddie Stimulus discrimination is taught by using discrimination training procedures such as differential reinforcement

Stimulus Control Stimulus Generalization Definition: When a response is reinforced in the presence of one stimulus there is a general tendency to respond in the presence of new stimuli that have similar physical properties ore have been associated with the stimulus. loose degree of stimulus control E.g., All men with beards are Daddy Cannot be taught –but can plan for it

Development of Stimulus Control Stimulus discrimination training Requires one behavior Two antecedent stimulus conditions (the SD and the S) Responses that occur in the presence of the SD are reinforced (thus, the response increases in the presence of the SD) Responses that occur in the presence of the S are not reinforced (this, the response decreases in the presence of the S Can also result in a lesser amount or quality of reinforcement

Development of Stimulus Control Example: Reinforcing a child’s saying “red” when someone asks “What’s your favorite color?” and witholding reinforcement if they said “red” when asked “ What’s your name?”

“What’s your favorite color?” SD: “What’s your favorite color?” Response: “red” Reinforcer: “Super! You said red!” SΔ: “What’s your name?” No praise

The Need for Discrimination Different antecedent stimuli often SHOULD differentially affect responding If this is not occurring, then we need to teach discrimination among stimuli Useful to be able to task analyze “discrimination” (it is much more complex than many interventionists are aware)

Why Teach Discriminations? Discrimination is a fundamental process that controls behavior. Discrimination allows us to differentiate when reinforcement is available for specific responses. For example, saying the word book when the teacher points to a book will result in reinforcement. Saying car when the teacher points to a book will not result in reinforcement. Also red light on the soda machine example.

Why Teach Discriminations? Many essential tasks require discrimination skills Reading. Labeling Objects. Following directions. Following activity schedules. Greeting people. Self-care skills.

Basic Problem of Discrimination Training Discrimination training teaches learners to perform a specific response in the presence of a specific stimulus and not to perform that response in the presence of other stimuli. Many individuals with developmental disabilities have difficulty learning discriminations Stimuli are compound (they consist of different elements) It may be difficult to control which element(s) of the stimulus exert control over behavior We must be careful how we teach and what stimuli we use!

Stimulus Compounding All stimuli are compound. They consist of many different elements. It is difficult to control which element or elements of the stimulus exert control over behavior. We need to be careful how we teach and what stimuli we use.

Differential Responding When a child’s behavior comes under the control of the SD, We say the SD has acquired stimulus control over the child’s behavior So the verbal stimulus “What’s your favorite color?” gains stimulus control over the response “red” – why? And the child is discriminating or responding differentially

“Simple” Discrimination I would argue that really is no such a thing but traditionally this refers to a fairly constant 3-term contingency: simplest way to teach discrimination is to reinforce a specific behavior in one situation (SD) and withhold reinforcement in the other (SΔ) “Stimulus control” refers to a change in behavior that occurs when either an SD or SΔ is presented. SD presented = probability of target response increases; SΔ presented = probability of same response decreases.

“Simple” Successive Discrimination One method is to arrange the presentation of SDs and SΔs so that one follows the other (called successive discrimination training). Teach behavior that is appropriate for each SD (or teach learner NOT to respond to an SΔ) See simple example next…

Learner receives reinforcement for taking the money

Learner receives NO reinforcement for taking the ball

“Simple” Simultaneous Discrimination In alternative procedure, simultaneous discrimination, the SD and multiple SΔs are presented at the same time and the learner responds to the SD.

Learner receives NO reinforcement for taking the clock or ball Learner receives reinforcement for taking the money

Matching or Conditional Discrimination In conditional discrimination training, the presence of a “sample stimulus” that changes from one trial to another (such as different instructions given to a learner) dictates which of two or more “comparison stimuli” the learner should select. In reality, this is what MOST real-world discriminations involve: the IF-THEN nature of the conditional discrimination

“Pick the money” “Pick the ball” One sample trial Another trial Learner receives reinforcement for taking the money Learner receives reinforcement for taking the ball

Conditional Discrimination behavioral function of an antecedent stimulus (i.e., the nickel or ball in the previous slide) changes depending on the presence of another stimulus (the different instructions in the previous slide). That is, sometimes a stimulus is an SD for pointing to it (or taking it) and in other situations is the SΔ for pointing to it (or taking it) the correct response is “conditional on” (dependent on) another antecedent stimulus CONDITIONAL DISCRIMINATION is an “IF-THEN” rule

Conditional Discrimination = Matching To Sample Because the conditional stimulus is referred to as a SAMPLE and the choices we respond to are called COMPARISON STIMULI, this is also called MATCHING TO SAMPLE (MTS) because learner needs to make a specific response to a specific comparison in the presence of a specific sample Examples…

Conditional Discrimination = Matching To Sample Identity matching (match one thing to itself)

Conditional Discrimination = Matching To Sample Perceptual similarity-based matching (e.g., match one dog picture to a similar dog picture)

Conditional Discrimination = Matching To Sample Arbitrary matching (e.g., match one dog picture to dissimilar stimulus such as a word) DOG HOP CAT

Possible Confounds in Conditional Discrimination (MTS) Training Also called “extraneous stimulus control” That is, something other than the teacher-defined antecedent stimuli is controlling behavior Often times, extraneous control can APPEAR to be “proper” stimulus control Let’s examine the following trials…

CAT

CAT

CAT

What’s the problem? Assuming you saw those 3 trials, would you say that the learner can match the written word CAT to a picture of a cat? What function might the sample or conditional stimulus (written word CAT) be serving? What is the problem with arranging trials in isolation this way?

What’s the problem? Now look at these 3 trials…

CAT

DOG

HAMSTER

What’s the problem? Assuming you saw those 3 trials, would you say that the learner can match the written word to corresponding picture? What function might the sample or conditional stimuli (written words) be serving? What is the problem with arranging trials in this way?

What’s the problem? Now look at some more trials…

DOG

DOG

DOG

What’s the problem? Assuming you saw those 3 trials, would you say that the learner can match the written word DOG to the corresponding dog picture? What function might the sample or conditional stimulus (written word) be serving? What is the problem with arranging trials in this way? ARE THE NOVEL DISTRACTORS RELEVANT??

What’s the problem? Here are some more trials

DOG

DOG

DOG

DOG

What’s the problem? Assuming you saw those 3 trials, would you say that the learner can match the written word DOG to the corresponding dog picture? What function might the sample or conditional stimulus (written word) be serving? What is the problem with arranging trials in this way?

Strategies to Reduce Extraneous Stimulus Control in MTS Within a session, alternate sample stimuli. Why? Each sample should appear in an equal number of trials. Why? Use the SAME comparisons within a session during training. Why? Use at least 3 comparisons on every trial. Why? What is the limit on number of comparisons?

More Strategies to Reduce Extraneous Stimulus Control in MTS Within a session, the correct comparison stimuli should appear equally often (frequency of occurrence) Within a session, the correct comparison stimuli should appear equally often in EACH POSITION

More Strategies to Reduce Extraneous Stimulus Control in MTS For each trials, the learner should be required to make an OBSERVING RESPONSE to the sample (conditional) stimulus. Why? Do not rearrange the trial stimuli in front of the learner. Screen these and then present them in the “proper” array. (This could be a good thesis project in which you do alternating treatments of “screened” trails vs. “unscreened” trials. Would be published in a second whether there was a difference or not!)

More Strategies to Reduce Extraneous Stimulus Control in MTS Have learners POINT to the correct comparisons rather than PLACE ON TOP of the sample stimulus. Why? (This could also be a good thesis project in which you do alternating treatments of “pointing” trials vs. “place on top” trials. Would be published in a second whether there was a difference or not!)

More Strategies to Reduce Extraneous Stimulus Control in MTS Use ERRORLESS TEACHING rather than TRIAL N’ ERROR Idea here is that we can reduce emotional side effects of trial and error Can reduce likelihood that an extraneous source of control has been adventitiously reinforced during trial and error How can you use errorless teaching?

Discrimination in the Laboratory. Many laboratory discrimination procedures have focused on understanding exactly which stimuli or which aspects of stimuli control responding. Several laboratory procedures have been developed that allow us to isolate these stimulus control factors. Matching-to-Sample. Equivalence Class Formation.

Stimulus Class Stimulus Class: set of stimuli that have a common effect on behavior (evoke the same response class) These would probably be in the same stimulus class for most people

Concept Formation Complex stimulus control that results in: Generalization within a class of stimuli and Discrimination between classes of stimuli

Two Procedures to Teach Concept Formation: Simultaneous Discrimination: Definition: The concurrent presentation of multiple stimuli Successive Discrimination Definition: The successive presentation of stimuli In applied settings, simultaneous discrimination training should be used –why? The individual has access to all relevant stimulus cues at one time An on the spot comparison of choices is permitted Produces better generalization (Schroeder & Baer, 1972)

Classroom Teaching Procedures. Classroom teaching is more complex than the laboratory. Suggestions for improving discrimination training Evaluate stimuli carefully to promote control of relevant antecedent cues Rotate stimulus placement randomly Change auditory stimuli frequently Be sure that the S+/S- functions of stimuli change randomly Teach with a variety of stimuli to promote discrimination between categories (and generalization within categories) Never, never teach in isolation!!

Classroom Teaching Procedures. NEVER, NEVER, NEVER teach in isolation!!

Equivalence Classes: Definition a finite group of physically disparate stimuli (no perceptual similarity) stimuli become related solely as a function of teaching (Fields, Adams, Buffington, Yang, & Verhave, 1996; Fields, Reeve, Adams, Brown, & Verhave, 1991; Sidman & Tailby, 1982; Sidman, 1994) Emergence of accurate responding to untrained and nonreinforced stimulus-stimulus relations Following the reinforcement of responses to some stimulus-stimulus relations An equivalence class must contain at least three stimuli (but often has many more)

Example Stimuli in a 3-Member Equivalence Class Written word Spoken word A picture DOG “DOG”

Another Example Written word Spoken word A picture CAT “CAT”

Stimulus Equivalence Train: Emergent Relations: Symmetry: B  A and CB Transitivity: A  C Equivalence: C  A DOG “dog” B C A

Teaching & Testing Summary We TAUGHT 2 conditional relations: A  B B  C We TESTED for 4 EMERGENT (DERIVED) relations: B  A symmetry C  B symmetry A  C transitivity C  A equivalence (Another set of tests for REFLEXIVITY (IDENTITY) is often omitted if the learner already has this skill in her repertoire: A  A; B  B; C  C )

Factors Affecting the Development of Stimulus Control Reinforcement Differential reinforcement with rich schedules of reinforcement Preattending Skills Looking at instructor or materials, sitting up tall, no stereotypy

Factors Affecting the Development of Stimulus Control Stimulus Presentation Specificity of directions Should relate to response definition Opportunity to response Frequent, active opportunities to respond (active student learning) correctly leads to higher rates of academic achievement Pacing of response opportunities Higher pace often leads to superior performance and less off-task behavior

Factors Affecting the Development of Stimulus Control Salience of the stimuli Influences attention and ultimately the development of stimulus control Dependent on the capabilities of an individual, the past history of reinforcement, and the situation Multiple intelligences: some respond to instructional stimuli in the visual modality more than the oral. This research has generated mixed results but it is important to rule out sensory deficits and assess modality strength

Factors Affecting the Development of Stimulus ontrol Masking and overshadowing Masking –even though one stimulus has control over behavior, another stimulus blocks that control from being expressed E.g., Student knows answer but won’t answer in front of peers Overshadowing –the presence of one stimulus condition interferes with the acquisition of control by another stimulus E.g., hallway may be more interesting that teacher’s presentation in the front of the classroom Ways to overcome include to make changes to physical environment, make instructional stimuli as intense and centrally located as possible, reinforce behavior in the presence of the instructionally relevant stimuli

Equivalence Class Training & Testing Procedures Usually taught and tested with arbitrary match-to-sample (MTS) Symbolic notation is used to outline training/testing procedures: A, B, C, …N represent each of the disparate stimuli that will make up the class 1, 2, 3, etc. notate the number of classes to be established Thus, A1 = first stimulus in class 1; B3 = second stimulus in class 3; etc.

Training & Testing Procedures To establish equivalence classes, at least two potential classes must be trained concurrently training establishes both substitutability of all stimuli within a particular equivalence class in addition to discrimination between classes

Training & Testing Procedures To establish equivalence classes with three members, at least two stimulus-stimulus relations must be trained for each potential class Let’s consider our DOG and CAT potential equivalence classes First train the AB relation (given stimulus A select stimulus B) the word DOG (A1) is presented as a sample The positive comparison (Co+) would be the spoken word dog (B1) (Selection would result in positive feedback or reinforcement) the negative comparison (Co-) would be the spoken word cat (B2) (Selection would result in corrective feedback or no reinforcement)

Training AB relation DOG A1 CAT DOG B1 B2

Training & Testing Procedures To train the AB relation word CAT (A2) is presented as a sample positive comparison (Co+) would be the spoken word cat (B2) (Selection would result in positive feedback or reinforcement) negative comparison (Co-) would be the spoken word dog (B2) (Selection would result in corrective feedback or extinction)

Training AB relation CAT A2 CAT DOG B1 B2

Training & Testing Procedures Once responding is 100% correct, we can conclude AB conditional relation has been learned At this point we can either continue training more conditional discriminations or we can do our first test for an EMERGENT (DERIVED) RELATION (a conditional discrimination that emerges with no direct training history) If the learner “knows” that A goes with B, can they demonstrate the reverse? (B goes with A) This emergent relation shows SYMMETRY

TESTING BA symmetry relation CAT B2 CAT DOG A1 A2

TESTING BA symmetry relation DOG B1 CAT DOG A1 A2

Training & Testing Procedures the BA conditional relation is called “symmetry” because the relation is a mirror image or reversal of the one directly trained (i.e., A=B then B=A) At this point, we can continue training another conditional discrimination Let’s train the BC conditional relation

Training BC relation DOG B1 C2 C1

Training BC relation CAT B2 C2 C1

Training & Testing Procedures Once the BC conditional relation is learned, we can do our 2nd test for an EMERGENT (DERIVED) RELATION If the learner “knows” that B goes with C, can they demonstrate the reverse? (C goes with B) This emergent relation would show a SECOND SYMMETRY relation

TESTING CB symmetry relation DOG CAT B1 B2

TESTING CB symmetry relation DOG CAT B1 B2

Training & Testing Procedures If CB symmetry TEST responding is 100% correct, we can continue testing for another EMERGENT (DERIVED) RELATION If the learner “knows” that A goes with B, and B goes with C, can they demonstrate that A goes with C? This emergent relation would show a TRANSITIVE relation

TESTING AC transitive relation DOG A1 C2 C1

TESTING AC transitive relation CAT A2 C2 C1

Training & Testing Procedures If the AC transitive TEST responding is 100% correct, we have one last test for another EMERGENT (DERIVED) RELATION If the learner “knows” that A goes with B, and B goes with C, can they demonstrate that C goes with A? This emergent relation would shows a combination of symmetry and transitivity; it is called an EQUIVALENCE relation

TESTING CA equivalence relation CAT DOG A2 A1

TESTING CA equivalence relation CAT DOG A2 A1

Teaching & Testing Summary We TAUGHT 2 conditional relations: A  B B  C We TESTED for 4 EMERGENT (DERIVED) relations: B  A symmetry C  B symmetry A  C transitivity C  A equivalence (Another set of tests for REFLEXIVITY (IDENTITY) is often omitted if the learner already has this skill in her repertoire: A  A; B  B; C  C )