Investigating the Use of a Blocked Trial Procedure to Facilitate
Conditional Discriminations
Nicholas K. Reetz, Paula Petit, Sarah Camp, Valerie VanTussi, Brianne Larson, & Kevin P. Klatt
Psychology Department, University of Wisconsin-Eau Claire
Results
Introduction
A skill repertoire is a set of skills that share several attributes. For example,
correctly following the instructions “touch nose,” “touch head,” “touch belly,” and
“touch foot” all fall into the skill repertoire of being able to touch body parts when
instructed to do so.
Behavioral therapists, who use behavioral principles to teach skills, typically
teach one skill within a behavior repertoire to mastery before teaching another
skill within the same repertoire. A fairly common problem exhibited by children
with profound cases of autism is the inability to consistently and correctly
discriminate between previously isolated skills from a developing repertoire when
instructions to perform those skills are randomized.
Little to no research addresses how to teach the ability to discriminate to young
children with autism who are in the process of building simple skill repertoires
(e.g., motor imitation, receptive identification of body parts, etc.). The inability to
discriminate can significantly slow the acquisition of new skills in a child's
developing repertoire and may be attributed to a lack of stimulus control. The
current study investigated the use of a blocked trial procedure (Saunders &
Spradlin, 1993) to facilitate conditional skill discriminations.
Method
• The participant was a 4.5 year old girl diagnosed with autism spectrum disorder.
• Experimental sessions were run during normally scheduled therapy sessions.
• Skills were taught in isolation of one another by the participant’s therapy team
before the discrimination between the skills was taught.
• Sessions were terminated if severe problem behavior occurred or if the
participant made six consecutive errors.
• The participant was taught to discriminate between two sets of skills, with each
set consisting of two skills:
Discrimination Set 1: Skill 1 = Touch Nose; Skill 2 = Touch Foot
Discrimination Set 2: Skill 1 = Touch Belly; Skill 2 = Touch Head
• 18 trials were scheduled to be presented for each discrimination set being run.
• Incorrect responses were not followed by a correction procedure.
Trial:
Establishment of Motivating Operation
Instruction
Correct Response
Receipt of Reinforcer
Establishment of Motivating Operation
Instruction
Incorrect Response
No consequence
*All responses in baseline sessions were followed by no scheduled consequences.
Block Types:
Baseline = randomized trials of skills 1 and 2
Block Type 1 = 18-trial block of skill 1
Block Type 2 = 18-trial block of skill 2
Block Type 3 = 9-trial blocks of skills 1 and 2
Block Type 4 = 6-trial blocks of skills 1 and 2
Block Type 5 = 4-trial blocks of skills 1 and 2
Block Type 6 = 3-trial blocks of skills 1 and 2
Block Type 7 = randomized 2-trial, 3-trial, and 4-trial blocks of skills 1 and 2
Block Type 8 = randomized trials of skills 1 and 2
*The criteria needed to progress to the next scheduled block type was correct
responding to at least 85% of trials presented across two consecutive days.
Maintenance Probe:
• Occurred directly before 18 trial experimental session
Establishment of Motivating Operation
Instruction
Correct Response
Begin 18 trial
experimental session
Incorrect Response
Two prompted trials
Begin 18 trial
Block Type 8 (Terminal Condition) Probe:
experimental session
• Probes occurred on sessions following the meeting of mastery criteria for a discrimination block type.
• Followed typical trial format.
• This manipulation allowed the researchers to track the participant’s ability to discriminate between
randomly presented trials.
• Baseline data indicated that the participant could not discriminate between the skills in each
skill set.
• In Discrimination Set 1, the participant took nearly one month to meet the mastery criteria for
Block Type 3. In Discrimination Set 2, the participant took two days to meet the mastery criteria
for Block Type 3.
• The participant was able to meet mastery criteria in less sessions as she progressed through
block types in Discrimination Set 1.
• Data taken from the terminal condition probes in Discrimination Set 1 displayed an upward
trending curve.
• In Discrimination Set 1, the participant met the percentage correct specified by the mastery
criteria on a Block Type 8 probe after Block Type 6. In Discrimination Set 2, the participant met
the percentage correct specified by the mastery criteria on a Block Type 8 probe after Block
Type 4.
Discussion
• The sole use of a blocked trial procedure does not appear to immediately establish
effective stimulus control of an instruction over a response.
• Supplemental methodological adjustments (e.g., the use of a preceding
maintenance probe, the use of vocal prompts, etc.) appear necessary to effectively
establish initial stimulus control of an instruction over a response.
• No supplemental methodological adjustments were needed to maintain effective
stimulus control after the most basic discrimination task (i.e., Block Type 3) had been
mastered.
• As shown by the upward trending curve of the Block Type 8 probe data points in
Discrimination Set 1, the participant was better able to complete difficult
discrimination tasks (i.e., Block Type 8) after mastering easier discrimination tasks.
• The acquisition of the ability to discriminate between two skills (i.e., Discrimination
Set 2) appears to occur more rapidly after the mastery of previously taught
discriminations (i.e., Discrimination Set 1).
• The ability to discriminate between two skills, as taught by the use of a blocked trial
procedure, appears to maintain in general. If a loss of the ability to discriminate
between two skills occurs, re-applying the blocked trial procedure appears to reestablish the ability to discriminate.
Support for this project came both from the Office of Research and Sponsored Programs and from Differential Tuition through the
UWEC Student Travel for the Presentation of Research Results Program.