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Keywords:

  • differential reinforcement;
  • intellectual disabilities;
  • prompt dependence;
  • skill acquisition

Abstract

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS AND DISCUSSION
  5. REFERENCES

We compared the effects of varying reinforcement schedules on independent responding with 3 individuals with intellectual disabilities. Independent responding was always reinforced, and responding after a vocal response was either (a) always reinforced, (b) never reinforced, or (c) reinforced on a fixed-ratio 3 schedule. Results showed that for 2 of the 3 participants, independent responding was higher when responding after the vocal prompt was never reinforced. These data suggest that altering the reinforcement schedule to favor independent responding may lead to increased independent responding.

Prompting hierarchies (e.g., least-to-most prompting) are commonly used to teach new skills to individuals who have been diagnosed with intellectual disabilities (e.g., Horner & Keilitz, 1975). However, these prompting strategies may result in prompt dependence if the learner attends to prompts rather than the relevant task stimuli. Prompt dependence has been described as responding to prompts rather than within-stimulus cues that are expected to evoke the relevant response (Cameron, Ainsleigh, & Bird, 1992).

Differential reinforcement of responses that occur independently may be an important consideration when teaching new skills. By programming a denser reinforcement schedule for correct, independent responding (relative to prompted responding), individuals might begin to respond before the prompt. Results from several studies have suggested that differential reinforcement may be an effective means of increasing more independent responses (Karsten & Carr, 2009; Olenick & Pear, 1980; Touchette & Howard, 1984). The purpose of the current study was to examine further whether arranging schedules of reinforcement to favor independent responding would result in increased levels of independent (unprompted) responding among individuals with intellectual disabilities.

METHOD

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS AND DISCUSSION
  5. REFERENCES
Participants and Setting

Three adolescents and young adults who had been diagnosed with intellectual disabilities were selected for participation in this study. All participants were recruited from an inpatient unit where they had been admitted for the assessment and treatment of severe problem behavior. Sam was a 16-year-old boy whose diagnoses included autism and mild intellectual disability. Mike was an 18-year-old man whose diagnoses included autism and intellectual disability, severity unspecified. Peter was a 20-year-old man whose diagnoses included autism and intellectual disability, severity unspecified. Problem behaviors for all participants were treated in a separate evaluation, independent of this study. None of the participants was found to engage in escape-maintained problem behavior; however, all participants were identified as having low levels of compliance during daily academic sessions. For Sam and Mike, sessions were conducted in a classroom. For Peter, sessions were conducted in a bedroom. Rooms contained a table, two chairs, and demand materials.

Response Definitions, Data Collection, and Interobserver Agreement

Independent responding was defined as correctly completing the task (i.e., filling in the missing letters to spell the target word correctly or matching a coin to its correct value) within 5 s or 10 s (depending on the participant) of the presentation of task materials but before the vocal prompt. Observers used paper and pencil to collect data on the frequency of correct responses that occurred at each level of prompting. Frequency data were converted to percentage of correct responses. A second observer independently collected data during 40%, 42%, and 48% of sessions for Sam, Mike, and Peter, respectively. Interobserver agreement was calculated by dividing the number of trials in agreement by total number of trials and converting the result to a percentage; agreement averaged 99.6%, 99%, and 99.6% for Sam, Mike, and Peter, respectively (range, 90% to 100% for all participants).

General Procedure

The three most highly preferred edible items identified via paired-choice preference assessments (Fisher et al., 1992) were selected for use throughout this evaluation. Two similar, visual–visual simple discrimination tasks were chosen for each participant based on information obtained, in part, from each participant's individualized education plan. Sessions consisted of 10 trials of a task. One sample stimulus and four comparison stimuli (one S+ and three S− cards) were presented during each trial. For Sam, a spelling task was selected. Two letters were removed from each word of the four comparison stimuli, and the sample stimuli (the corresponding letters) were placed in front of him at the start of each trial. The target response for Sam was correctly filling in the missing letters to spell horses and orange. The target responses for Mike included matching a penny or a quarter to the correct value. Similarly, Peter's target response was matching a nickel and a quarter to their correct values. For all participants, the trial began when the experimenter placed the sample stimulus, either the two missing letters (Sam) or the coin (Mike and Peter), on the table in front of the participant. The positions of the comparison stimuli (i.e., S+ and S− cards) were randomly rotated from trial to trial. To further enhance discrimination, an S− card from one task did not function as an S− in the other task. That is, stimulus sets that consisted of three S− and one S+ cards were created for each task, and these sets were held constant across tasks.

The stimuli contained in each task were randomly assigned to one of two test conditions. Least-to-most prompting, consisting of a vocal, gestural, and full physical prompt hierarchy (Horner & Keilitz, 1975), was used during all conditions except baseline. A 5-s (Sam and Mike) or 10-s (Peter) delay was in effect before initiation of the prompting sequence, and either a 5-s or 10-s delay was also programmed between each step of the prompting hierarchy (i.e., a constant prompt delay). A 5-s delay was selected for Sam and Mike because this was the standard prompt delay used on the inpatient unit when demands were presented (e.g., during academics). A longer delay was programmed for Peter based on educational recommendations, because he was often slower to respond to requests. Praise and a preferred edible item, chosen by the participant before each session, were delivered during all test conditions for correct responses according to the reinforcement schedule. Praise was provided for compliance after the gestural prompt. No praise was provided after full physical prompting.

Conditions
Baseline

Only the vocal prompt was delivered each trial. The vocal prompt delivered across conditions was specific to the task (e.g., “spell [word]” or “match [coin]”). The trial began when the experimenter placed either the two missing letters (Sam) or the coin (Mike and Peter) on the table. If no responding occurred within 5 s or 10 s of stimulus presentation or if the participant emitted an incorrect response, the vocal prompt was initiated. The trial ended after 5 s or 10 s had elapsed after the vocal prompt with no response or if the participant emitted an incorrect response. Praise (e.g., “Nice job doing your work.”) was delivered contingent on correct independent responding or compliance after the vocal prompt. No consequences were provided for incorrect responses. The S+ and S− cards were randomly rotated from trial to trial.

CRF/CRF

The experimenter delivered praise and an edible item following both correct independent responding and compliance with the vocal prompt on a continuous (i.e., fixed-ratio [FR] 1) schedule.

CRF/EXT

Correct independent responding resulted in the delivery of an edible item and praise on an FR 1 schedule. Compliance after the vocal prompt resulted in praise only.

CRF/FR 3

The experimenter delivered an edible item and praise on an FR 1 schedule for correct independent responding and on an FR 3 schedule for compliance after the vocal prompt.

Design

A combination nonconcurrent multiple baseline design across participants and multielement design was used to evaluate the effects of the schedule manipulations. Different-colored placemats were used to aid in discrimination between reinforcement schedules in effect. Condition-specific therapists also were used to enhance discrimination between the CRF/EXT and CRF/FR 3 conditions during the multielement comparison. If differentiation in levels of responding was observed between the CRF/EXT and CRF/FR 3 conditions, an additional phase was conducted in which the task used in the condition with lower levels of responding (e.g., the CRF/FR 3 condition) was assigned to the schedule in the condition previously associated with higher levels of responding (e.g., the CRF/EXT condition).

RESULTS AND DISCUSSION

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS AND DISCUSSION
  5. REFERENCES

Figure 1 shows percentage of correct independent responding for all three participants. During baseline, Sam and Mike did not emit correct independent responses, and Peter engaged in low levels of correct independent responding across tasks. The initial CRF/CRF condition resulted in modest increases in correct independent responding for all three participants. Correct independent responding increased following the introduction of the CRF/EXT and CRF/FR 3 conditions for both Sam and Mike; however, correct independent responding was usually higher during the CRF/EXT condition. Finally, for Sam and Mike, correct independent responding for the task previously associated with the CRF/FR 3 schedule increased when the schedule was changed to CRF/EXT. For Peter, an initial increase in correct independent responding was not observed in the CRF/EXT or CRF/FR 3 conditions. However, as this phase continued, responding increased at similar levels in both conditions.

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Figure 1. Percentage of correct independent responding across conditions.

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These findings suggest that, for some individuals, a more timely transfer of stimulus control from the prompt to the task stimuli may be facilitated by arranging reinforcement contingencies to favor correct independent responses such that the participant receives highly preferred items only after a correct independent response, as in the CRF/EXT condition. These data lend additional support to research that has shown that differential reinforcement is effective in increasing correct unprompted responding (Karsten & Carr, 2009; Olenick & Pear, 1980; Touchette & Howard, 1984). The CRF/CRF and CRF/FR 3 conditions used in this study were similar to those evaluated by Touchette and Howard (1984). The rationale for including the CRF/EXT condition in the current study was to determine if greater increases in independent responding would be observed when reinforcement was available only for responses that occurred independently.

It is plausible that differences in the delay to reinforcement and subsequent differences in the rate of reinforcement available for unprompted and prompted responses could have influenced the current findings. The delay to reinforcement following correct unprompted responses was shorter than the delay to reinforcement following prompted responses, even when the reinforcement schedule was held constant (i.e., during the CRF/CRF condition). The disparity in the delay to reinforcement following unprompted and prompted responses was even greater in the CRF/FR 3 condition. In addition to acquiring reinforcers more immediately, more reinforcers could be earned in a given session by engaging in correct unprompted responses. During the CRF/EXT condition, the only way to access preferred edible items was to engage in correct unprompted responses.

Results have several implications. First, delivering reinforcement contingent on the desired level of independent responding is likely to encourage high levels of unprompted responding in the future. However, it might be advantageous to program a CRF/CRF schedule when introducing a new skill such that correct responses contact reinforcement before differentially reinforcing only independent responses. Second, it is also possible that delivering reinforcement after only independent responses results in higher levels of independent responding that could, in turn, result in more rapid acquisition of new skills. Therefore, more tasks could be taught within a given amount of time, increasing the student's behavioral repertoire and overall level of independence.

REFERENCES

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS AND DISCUSSION
  5. REFERENCES
  • Action Editor, Michael Kelley