Stimulus Control Procedures to Facilitate Visual ... · 6 Stimulus-Prompt Procedures Stimulus...
Transcript of Stimulus Control Procedures to Facilitate Visual ... · 6 Stimulus-Prompt Procedures Stimulus...
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Stimulus Control &
Procedures to Facilitate Visual Discriminations
David M. Wilson, Ph.D., BCBA-D
Georgian Court University
Agenda
Visual Discrimination
Stimulus Control
Review procedures to transfer stimulus control
Brief review of comparison studies
Study: Procedures to facilitate discrimination
Summary
Questions
Visual Discrimination
Discrimination: differentially responding in the
presence of different stimuli
Critical for learning
Discrimination among complex stimuli
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Visual Discrimination
Students must discriminate academic materials:
– Colors & Shapes
– Image credit: https://creativemarket.com/blog/2013/12/02/10-basic-elements-of-design
Visual Discrimination
– Numbers & Letters
http://studentmedia.uab.edu/wp-content/uploads/2012/09/123ABC.jpg
Visual Discrimination
– Words & Pictures
Image credit( (http://www.uniqueteachingresources.com/reading-sight-words.html
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Visual Discrimination
Other discriminations:
Visual Discrimination
Individuals with Intellectual/Developmental
Disabilities (I/DD) and/or Autism may not acquire
visual discriminations under standard teaching
conditions
A variety of procedures have been described to
facilitate learning visual discriminations
Let’s Review the Basics
Stimulus Control
Change in property of stimulus produces change
in rate or probability of a response (Rilling, 1977)
– Responding differently to different stimuli
Established via differential reinforcement (e.g.,
Reynolds, 1960; Eckerman, 1969)
– S+: stimuli correlated with reinforcement
– S-: stimuli correlated with no reinforcement
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Stimulus Control
S+S-
“Press Me”
RE
INF
OR
CE
ME
NT
Stimulus Control
S+ S-
Bar 1
RE
INF
OR
CE
ME
NT
Bar 2
Stimulus Control
Differential Reinforcement can be effective to
establish stimulus control
Limitations:– Errors (responses to S-) occur during teaching
– Prolonged teaching sessions
– Learners may never acquire the correct responses
Alternative teaching methods must be considered
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Errorless Learning
Errorless learning or Errorless discrimination
Training involves the use of a fading procedure to
establish a discrimination so that no errors occur.
Fading involves the gradual removal of:– Stimulus prompts
– Response prompts
Errorless Learning
Trials 1-10Trials 11-15Trials 16-20Trials 21-25Trials 26-30Trials 31-35 A B
Transfer of Stimulus Control
Transfer of Stimulus Control:– Procedures to fade prompts
– Transfer stimulus control from a prompt to a
feature of the target stimulus
2 Categories:1. Stimulus-prompt procedures
2. Response-prompt procedures
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Stimulus-Prompt Procedures
Stimulus Fading:– Adding stimuli to, or enhancing teaching stimuli
Size
Color
Position
Texture
– Gradually remove (fade) enhancements
– End with target teaching stimuli
Stimulus Fading
Letter Discrimination:
Target stimuli: A B
Step 1: B
Step 2: B
Step 3: A B
Stimulus-Prompt Procedures
Stimulus Shaping:– Manipulating the topography (shape) of teaching
stimuli
– Gradually fade, or change the shape, the enhanced
stimuli
– End with the target teaching stimuli
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Stimulus Shaping
Stimulus-Prompt Procedures
Advantages: – Enhancements are made to the actual target stimuli
– Facilitates transfer to relevant stimulus features
Disadvantage:– Making enhanced stimuli takes time
– Teaching time may be extended
Extra-stimulus prompt:– Not related to the discrimination task
Point prompt Most-to-least prompting Least-to-most prompting Verbal prompt
Response-Prompt Procedures
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Prompt Delay:– Incorporated into extra-stimulus prompt procedures
– Inserts a delay between target stimuli presentation and
extra-stimulus prompt
– Reinforcement arranged to favor responses before the
prompt
Prompt Delay
“Touch A”
A B
Response-Prompt Procedures
Response-Prompt Procedures
Advantages: – Most-to-least produces fewer errors, rapid
acquisition
– Least-to-most allows for independent responding
Disadvantages:– Extra-stimulus prompts are not relevant to target
stimuli
– May be difficult to fade
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What procedure works best?
It depends…..
Summary of Comparison Studies
Stimulus-prompt superior to reinforcement-ext: – Egeland and Winer (1974)
– Egeland (1975)
– Schilmoeller, Etzel, and LeBlanc (1979)
Stimulus-prompt superior to response-prompt:– Schreibman (1975)
– Repp, Karsh, and Lenz (1990)
Fade along dimensions of the S+ rather than S-:– Schreibman and Charlop (1981)
– Strand (1989)
Other Considerations
Does the procedure lead to the
stimuli that “should” control behavior?
Number of fading steps
Conducting probe trials (presenting target stimuli)
Criterion for advancing/revisiting steps
Fading along multiple dimensions
Combining fading procedures
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Other Considerations
Restricted Stimulus Control (aka stimulus
overselectivity)– Possible feature of autism
– Responding under control of irrelevant feature of a
complex stimulus Position
Specific therapist/teacher
Tear in the left hand corner of an instructional stimulus
Other Considerations
Addressing restricted stimulus control– Eliminate irrelevant feature (if possible)
– Transfer control to relevant feature of target stimulus
– Alternate between teaching trials of target stimulus with
problem stimulus
Examination of Procedures to Facilitate
Discrimination of Picture-Communication Cards
Wilson, D.M., Iwata, B.A.
&
Bloom, S.E.
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PECS (Bondy & Frost, 1994, 2001)
Augmentative communication system
Utilizes picture cards containing
communicative referents
6 Training Phases (1-3 critical):– Phase 1: Requesting
– Phase 2: Generalization
– Phase 3: Discrimination
PECS Curriculum
(Frost & Bondy, 1994, 2001)
PECS
PECS usage is rapidly acquired: – Bondy and Frost (1994, 2001)
Increases vocal communication: – Kravits, Kamps, Kemmer, and Potucek (2002)
– Charlop-Christy, Carpenter, LeBlanc, & Kellet
(2002)
Decrease inappropriate behaviors:– Charlop-Christy, Carpenter, LeBlanc, & Kellet
(2002)
What about participants who have difficulty
acquiring PECS usage?
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Purpose
Study 1: compare methods for facilitating
discrimination during picture-card
communication training
– Antecedent: stimulus fading
– Consequence: enhanced (magnitude/quality)
Study 2: evaluate the effects of stimulus fading
combined with enhanced consequences to train
discrimination between two picture cards
Study 1: Methods
Participants and Setting:
– 3 participants with developmental disabilities
– Sessions conducted at sheltered workshop
General sequence:
– Preference assessment
– Single-card training
– Discrimination baseline
– Multielement comparison of stimulus fading
vs. enhanced consequences
– Multiple-baseline across participants
Preference Assessments
Paired-stimulus method (Fisher et al.,
1992):
– Selection ≥ 80% → S+
– Selection ≤ 20% → S-
Single-stimulus method (Pace et al., 1985):
– Selection = 0% → S-
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Discrimination Baseline
• S+ & S- presented:- S+ → access to corresponding stimulus
- S- → access to corresponding stimulus
- No response → next trial
• S+/S- positions alternated • Criterion for continuation: failure to meet
criterion of 90% unprompted correct
responses for 3 consecutive sessions
Comparison Methodology
One S+/S- pair taught via stimulus fading
Another S+/S- pair taught via enhanced
consequences
Training sessions alternated
Criterion: 90% responding to S+ for 3
consecutive sessions under original S+/S-
conditions
Stimulus Fading
Enhanced S+ card:
– Distance
– Size
Fading steps:
– Fading criterion: S+ responding 90% or higher
for 3 consecutive sessions
– Distance: 10 cm, 20 cm, 30 cm
– Size of card: 10 cm2, 7.5 cm2, 5 cm2, 2.5 cm2
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Picture Cards
S+ S-
Stimulus Fading S+
Enhanced Consequences
Rate, delay, magnitude, quality:
– Magnitude (Hoch, McComas, Johnson,
Faranda, & Guenther, 2002)
– Quality (Mace, Neef, Shade, & Mauro, 1996)
Enhanced Consequences
Magnitude:
– Response to S+: larger quantity of reinforcers
(e.g., 3 jellybeans)
– Thinning: S+ responding 90% or higher for 3
consecutive sessions
Quality:
– S- replaced with stimulus never selected during
the single-stimulus preference assessment
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Paired-Stimulus Preference
Assessment
0
25
50
75
100
% S
elec
ted
RK
Tre
at
Dori
to
M &
M
PB
Bit
e
Pre
tzel
Tw
izzl
er
Gum
mi
Puff
ed W
hea
t
Skit
tle
S+
S-
0
25
50
75
100
Gum
Dro
p
PB
Bit
e
PB
M &
M
Dori
to
Pre
tzel
Tw
izzl
er
M &
M
Gold
fish
Puff
ed W
hea
t
Items
S+
S-
Al
Single-Stimulus Preference
Assessment
0
25
50
75
100
% S
elec
ted
Oli
ves
Pic
kle
d B
eets
Mu
shro
om
s
On
ions
Do
rito
s
Pre
tzel
s
Bla
ck L
ico
rice
Cau
lifl
ow
er
Rad
ish
Items
Al
S- (EC)
Discrimination TrainingBL
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Victor
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% o
f T
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s R
espondin
g w
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+
56 4 3 2
1
Al
6
3
45
2 1
56
3 2
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DiscriminationTraining
1
BL6
3
5 4
3 2
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0 50 100 150 200Sessions
Perry
3
6 45 3 2 1 6
3
34 2 15
1 *1
*1
DiscriminationTraining
3 2
6
3
Stimulus FadingEnhanced Consequences
1
5 4 3 2 1
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Summary of Results
Stimulus fading:
– Victor acquired 1 S+/S- discrimination
– Perry acquired 3 S+/S- discriminations
Enhanced Consequences:
– Victor acquired 1 S+/S- discrimination
– Al acquired 2 S+/S- discriminations
Conclusions
Stimulus fading and enhanced consequences will facilitate visual discrimination
Enhanced consequences establishes stimulus control
Stimulus fading assumes stimulus control
Study 2
Purpose: evaluate the effects of stimulus fading
combined with enhanced consequences to train
discrimination between two picture cards
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Study 2: Methods
Participants and Setting:
– 5 participants w/ developmental disabilities
– Sheltered workshop or Special-Education School
Procedures identical to Study 1 (except
training)
Multiple baseline
Criterion: 90% responding to S+ for 3 consecutive sessions
Stimulus Fading &
Enhanced Consequences
Enhanced S+ card
Magnitude/Quality enhancement
Fading steps:
– Fading criterion: S+ responding 90% or
higher for 3 consecutive sessions
– Distance: 10 cm, 20 cm, 30 cm
– Size of card: 10 cm2, 7.5 cm2, 5 cm2, 2.5 cm2 ;
Reinforcer Magnitude: 3,2,1
Discrimination Training
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Andrew
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Billy
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Donald
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0 10 20 30 40 50 60 70 80 90 100
SESSIONS
Kevin
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% o
f T
rial
s R
esp
on
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g w
ith
S+
David
6 4 3 2 15 6 4 3 2 15BL1
BL2
StimulusFading
+ Enhanced
Consequences
6 4 3 2 1b5 6 4 3 251a 1b 1a
6 4 3 25 1 2 1b 1a 6 4 3 25 1b 1a 6 4 3 25 1b 1a
6 4 3 25 1 6 4 3 25 1 6 3 25 14
6 4 3 25 1
BL3
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Summary of Results
Stimulus Fading and Enhanced Consequences:
– Andrew & Billy acquired 2 S+/S- discriminations
– David & Donald acquired 3 S+/S- discriminations
– Kevin acquired 1 S+/S- discrimination
Average # of sessions for acquisition = 23
Conclusions
Study 1: Stimulus Fading and Enhanced Consequences were effective, but variability in results across participants
– Discrimination failures during baseline resulted from
different problems:
Indifference to consequences
Failure to attend to visual enhancements
Study 2: Stimulus Fading plus Enhanced Consequences was effective in preventing discrimination failures
Strengths Contributes to literature on picture-card
communication and stimulus control:
– Empirically assessed procedures
– Individual data analyzed
– Empirically identified S+/S-
– Combined procedure addressed possible
sources of discrimination failures
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Limitations
Training time
– Study 1: avg. 30 sessions
– Study 2: avg. 23 sessions
Number of fading steps
Picture card preparation time
Used only edible stimuli
Thank You