ABA Exam Coach

G.11: Shape dimensions of behavior.

Free practice questions for this part of the BCBA, with an explanation for every option.

A child currently sits at the table for 1 minute. The therapist reinforces sitting for 1.5 minutes, then 2 minutes, then 3 minutes, and so on until the child sits for 10 minutes. This is best described as:
  1. A. Chaining
    Chaining links different responses into a sequence.
  2. B. Stimulus fading
    Stimulus fading changes antecedent stimuli, not the criterion for reinforcing a response dimension.
  3. C. Shaping within a response topography (duration)
    Correct. Reinforcing successive approximations along one dimension of the same topography is shaping within a topography.
  4. D. Shaping across different response topographies
    The form of the behavior (sitting) stays the same. Only its duration changes.
While shaping vocal volume, a therapist raises the reinforcement criterion from 40 dB to 60 dB. The child's responses become less frequent, more variable, and the child starts to cry. What is the best course of action?
  1. A. Switch to an extinction procedure for quiet vocalizations
    Extinction is already in effect for the approximations the child can produce. That is the source of the problem.
  2. B. Provide reinforcement noncontingently to reduce the crying
    Noncontingent reinforcement would not reinforce successive approximations.
  3. C. Keep the 60-dB criterion so the child does not learn that crying lowers expectations
    A step that is too large effectively puts responding on extinction, which can produce emotional responding and loss of the behavior.
  4. D. Go back to a criterion the child was meeting and use smaller step sizes
    Correct. When responding falls apart, going back to the last successful approximation and making the steps smaller is good shaping practice.
A 3-year-old's speech goal is to say "ball." The therapist first reinforces any "b" sound, then only "ba," then only "bah-l," and finally only "ball" while the child plays with a ball. Earlier approximations are no longer reinforced once the next one is established. Which type of shaping is this?
  1. A. Shaping within a response topography
    Shaping within a topography keeps the form of the response the same and changes a dimension such as rate, duration, or magnitude. Here the form of the vocal response itself changes.
  2. B. Stimulus shaping
    Stimulus shaping gradually changes an antecedent stimulus. Here the learner's response is being changed through differential reinforcement.
  3. C. Response chaining
    Chaining links separate responses into a sequence, and each step stays part of the final performance. In shaping, earlier approximations are dropped as later ones are reinforced.
  4. D. Shaping across response topographies
    Correct. Reinforcing successively closer forms of a response ("b" → "ba" → "bah-l" → "ball") while extinguishing earlier forms is shaping across response topographies.

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