Stimulus Control

1
Stimulus Control

• Chapter 17

2
What is stimulus control?

• Stimulus control occurs when
• The rate, latency, duration, or amplitude of a
  response is altered
• In the presence of an antecedent stimulus
• Stimulus control is acquired when
• Responses are reinforced only in the presence of
  a specific stimulus
• Known as the discriminative stimulus (SD)
• And not in the presence of other stimuli
• Known as stimulus deltas (S??

3
The Development of Stimulus Control
SD
Response
SR
Friendly conversation
Telephone rings
Pick up phone and say hello
Response
S?
SO
Doorbell rings
Pick up phone and say hello
Friendly conversation withheld
4
Not to be confused with respondent conditioning
UCS
Response
Meat powder
Dog salivates
Response
Neutral S
Bell rings
Dog salivates
UCS
Meat powder
5
Not to be confused with respondent conditioning
CS
Response
Bell rings
Dog salivates
Notice the absence of any consequence stimuli in
this example. Salivating is a respondent
behavior. Also notice that here control is
established by pairing specific antecedent
stimuli.
6
Stimulus Control and Motivating Operations

• Similarities
• Both events occur before the behavior of interest
• Both events have evocative functions
• However, they are different!

7
Motivating Operations

• Remember, a motivating operation is something
  that changes the value of a stimulus as a
  reinforcer
• Establishing operation (EO) makes the reinforcer
  more valuable
• Abolishing operation (AO) makes the reinforcer
  less valuable

8
MOs and Stimulus Control
SR-
EO
SD
Response
Task break provided
Difficult Worksheet
Teacher 1
Student displays aggression
Response
SO
S?
EO
Teacher 2
Student displays aggression
Task break withheld
Difficult Worksheet
9
Stimulus Generalization

• Occurs when stimuli that share similar physical
  characteristics with the controlling stimulus
  evoke the same behavior as the controlling
  stimulus

10
Stimulus Discrimination

• Occurs when new stimuli that are similar to the
  controlling stimulus do not evoke the same
  response as the controlling stimulus

11
Stimulus Control and Stimulus Generalization are
a Continuum
Stimulus Control
Stimulus Generalization
12
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

13
The Development of Stimulus Control
SD
Response
SR
Friendly conversation
Telephone rings
Pick up phone and say hello
Response
S?
SO
Doorbell rings
Pick up phone and say hello
Friendly conversation withheld
14
Concept Formation

• Not a hypothetical construct or mental process
• Complex example of stimulus control that requires
• Stimulus generalization within a class of stimuli
• Stimulus discrimination between classes of stimuli

15
Example Concept of Red

• Stimulus generalization across all red objects
• Light red to dark red
• Different objects (car, ball, pencil)
• Stimulus discrimination between red and other
  colors
• Red ball vs. yellow ball
• Red dress vs. blue dress

16
Teaching Concepts

• Requires discrimination training
• Antecedent stimuli representative of a group of
  stimuli sharing a common relationship (examples)
  are presented, along with
• Antecedent stimuli from other stimulus classes
  (nonexamples)
• So that the examples form a stimulus class

17
Types of Stimulus Classes

• Feature stimulus class
• Stimuli share common physical forms (i.e.,
  topographical structures)
• Stimuli share common relative relationship (i.e.,
  spatial arrangements)
• Developed through stimulus generalization
• Arbitrary stimulus class
• Do not share a common stimulus feature
• Limited number of stimuli
• Developed using stimulus equivalence

18
Stimulus Equivalence

• The emergence of accurate responding to untrained
  and nonreinforced stimulus-stimulus relations
  following the reinforcement of responses to some
  stimulus-stimulus relations
• Useful for teaching complex verbal relations
• Reading
• Language arts
• Mathematics

19
Testing for Stimulus Equivalence

• Must have a positive demonstration on 3 different
  behavioral tests that represent the following
  mathematical statement
• If A B, and
• B C, then
• A C

20
Tests for Stimulus Equivalence

• Reflexivity
• Occurs when in the absence of training and
  reinforcement, a participant selects a stimulus
  that is matched to itself (A A)
• Matching to sample

21
Tests for Stimulus Equivalence

• Symmetry
• Occurs with reversibility of the sample stimulus
  and the comparison stimulus (if A B, then B
  A)
• Teach spoken word bicycle
• Present and participant matches to
• spoken word bicycle (as opposed to car or
  airplane)

22
Tests for Stimulus Equivalence

• Transitivity
• Requires demonstration of three untrained
  stimulus-stimulus sequences
• A B relation (spoken name picture)

Bicycle (spoken name presented)
(Child selects picture)
23
Tests for Stimulus Equivalence

• Transitivity
• Requires demonstration of three untrained
  stimulus-stimulus sequences
• B C relation (picture written word)

(picture presented)
bicycle
airplane
car
(Child selects written word)
24
Tests for Stimulus Equivalence

• Transitivity
• Requires demonstration of three untrained
  stimulus-stimulus sequences
• A C relation (spoken word written word)

(spoken word presented)
bicycle
bicycle
airplane
car
(Child selects written word)
25
Matching-to-Sample

• Participant observes the sample stimulus
• The comparison stimuli are then presented
• Participant makes a selection response
• Matches are reinforced
• Nonmatches are not reinforced

26
Matching-to-Sample

• Conditional discrimination training
• Same selection must be correct with one
  conditional stimulus, but incorrect with one or
  more other sample stimuli

Sample 1
Sample 2
27
Factors Affecting Stimulus Control

• Consistent use of reinforcers contingent upon
  correct responding in the presence of the SD is
  critical
• Also important are
• Pre-attending skills
• Stimulus salience
• Masking and overshadowing

28
Pre-attending

• A prerequisite skill for stimulus control
• Looking at instructional materials
• Looking at teacher when responses are modeled
• Listening to oral instructions
• Sitting quietly for short periods of time
• These may need to be taught before stimulus
  control procedures are implemented

29
Stimulus Salience

• Prominence of the stimulus in the environment
• Increased saliency facilitates efficiency of
  instruction

30
Masking and Overshadowing

• Increase or decrease salience of stimuli
• Competing stimuli may block the evocative
  function of an SD
• To limit the negative effects of these
• Rearrange the environment
• Make instructional stimuli more intense
• Consistently reinforce behavior in the presence
  of instructionally-relevant stimuli

31
Using Prompts

• Supplementary antecedent stimuli used to occasion
  a correct response in the presence of an SD (that
  will eventually control behavior)
• Response prompts operate directly on the response
• Stimulus prompts operate directly on the
  antecedent task stimuli

32
Response Prompts

• Verbal instructions
• Vocal
• Non-vocal (e.g., written)
• Modeling
• A demonstration of the desired behavior
• Physical Guidance
• Partially physically guide the students movements

33
Stimulus Prompts

• Movement cues
• Pointing, tapping, touching, looking at
• Position cues
• Place one stimulus closer to the student
• Redundance
• Stimulus or response dimensions are paired with
  correct choice

34
Transfer of Stimulus Control

• Prompts should be used only during acquisition
• Transfer stimulus control from prompt to
  naturally-existing stimuli quickly using fading

35
Transferring from Response Prompts

• Most-to-least prompts
• Physically guide participant through entire
  performance
• Gradually reduce amount of physical assistance
• Modeling
• Verbal instruction
• Natural stimulus

36
Transferring from Response Prompts

• Graduated guidance
• Immediately fade physical prompts
• Follow participant closely with hands
• Gradually increase distance between hands and
  participant

37
Transferring from Response Prompts

• Least-to-most prompts
• Provide participant with an opportunity to
  perform the response with the least amount of
  assistance on each trial
• Participant receives greater degrees of
  assistance with each successive trial without a
  correct response

38
Transferring from Response Prompts

• Time delay
• Varying the time interval between presentation of
  a natural stimulus and the presentation of a
  response prompt
• Constant time delay
• Begin with a 0-sec delay
• Then use a fixed delay (e.g., 3 sec)
• Progressive time delay
• Begin with a 0-sec delay
• Gradually and systematically increase delay
  (e.g., in 1-sec intervals) according to some rule

39
Transferring from Stimulus Prompts

• Stimulus fading
• Highlighting a physical dimension of a stimulus
  and then gradually fading that exaggerated
  dimension
• Superimposing one stimulus on top of another and
  gradually fading it out

40
Transferring from Stimulus Prompts

• Stimulus shape transformations
• Use an initial stimulus shape that will prompt a
  correct response
• This shape is gradually changed to form the
  natural stimulus, while maintaining correct
  responding