Biomedical subjects

Brian A Iwata

Publications and source records attributed to Brian A Iwata.

17 recordsLinked to original sources

PubMed2006

Establishment of mands following tact training as a function of reinforcer strength.

We examined some conditions under which a response acquired as a tact might facilitate the establishment of a mand. We taught 3 participants with developmental disabilities to tact the items ranked highest and lowest in a preference assessment and subsequently tested to see if the responses occurred as mands. All participants manded for the highly preferred item but rarely manded for the nonpreferred item. These results indicate that, although tact and mand functions are different, conditions can be created to facilitate transfer from the former to the latter. Implications for communication training are discussed.

Adult↗

PubMed2006

Some determinants of changes in preference over time.

Results of longitudinal studies suggest that the stability of preferences varies across individuals, although it is unclear what variables account for these differences. We extended this work by conducting periodic assessments of preference for leisure activities over 3 to 6 months with 10 adults with developmental disabilities. Although previous research has collectively shown that preferences identified via repeated assessment are highly variable, our results showed that preferences were relatively stable for the majority (80%) of participants. In an attempt to identify some environmental determinants of shifts in preference, we provided extended daily access to high-preference items (preference-weakening manipulation) and paired access to low-preference items with social and edible putative reinforcers during brief sessions (preference-strengthening manipulation). Preference assessments continued over the course of these manipulations with 2 participants. Results showed that changes in preference across time could be produced systematically and suggest that naturally occurring changes in establishing operations or conditioning histories contribute to temporal shifts in preference. Implications for preference assessments, reinforcer usage, and planned attempts to change preferences are discussed.

Adult↗

PubMed2005

Effects of stimulus variation on the reinforcing capability of nonpreferred stimuli.

We examined the effects of stimulus (reinforcer) variation in several different contexts. In Study 1, we identified high-quality (HQ) and low-quality (LQ) stimuli based on results of a paired-stimulus assessment and examined their effects when available under concurrent-reinforcement schedules for 8 participants. No participants showed preference for the LQ stimuli when compared singly or in a varied arrangement to the HQ stimulus. In Study 2, we identified nonpreferred (NP) stimuli based on results of a single-stimulus assessment and examined their effects when available under single-reinforcement schedules for 3 participants. Results of Study 2 were mixed. One participant's data indicated that the varied presentation of NP stimuli produced a modest improvement in performance over that observed when the stimuli were presented singly. By contrast, a second participant's data showed no facilitative effect for the varied delivery of NP stimuli and that the inclusion of an HQ stimulus in the varied arrangement obscured the reinforcing effects of the HQ stimulus. The 3rd participant's data showed no effect for the varied delivery of NP stimuli but an apparent facilitative effect when an HQ stimulus was included in the varied arrangement, which was attributable solely to the presence of the HQ stimulus.

Adult↗

PubMed2005

Analysis of response repetition as an error-correction strategy during sight-word reading.

A great deal is known about the effects of positive reinforcement on response acquisition; by contrast, much less research has been conducted on contingencies applied to errors. We examined the effects of response repetition as an error-correction procedure on the sight-word reading performance of 11 adults with developmental disabilities. Study 1 compared single-response (SR) repetition and multiple-response (MR) repetition, and results showed that all 6 participants acquired more sight words with the MR procedure. Study 2 compared MR error correction following every incorrect response (continuous) and following one third of incorrect responses (intermittent), and results showed that all 6 participants acquired more sight words when error correction was continuous. Study 3 compared MR error correction in which errors required practice of the training word (relevant) versus a different word (irrelevant), and results showed that 3 of 9 participants showed better performance under the relevant condition; however, all participants showed improvement even under the irrelevant condition. Findings are discussed in terms of the behavioral processes by which error correction may enhance performance during acquisition.

Adult↗

PubMed2005

A review of reinforcement control procedures.

A demonstration of the effects of reinforcement requires comparison of response rates in the presence of a contingency with those in another condition that controls for the influence of extraneous variables. We describe several control conditions that have been used in evaluating the effects of positive and negative reinforcement. The methodological rigor and practical utility of each type of control condition are discussed, and recommendations for the use of these conditions are presented.

Humans↗

PubMed2005

An analysis of response-blocking parameters in the prevention of pica.

We manipulated two parameters of response blocking to reduce pica: (a) the criteria for initiating the procedure (either earlier or later in the response chain) and (b) the distance from which the procedure was initiated. Results suggested that response blocking may be effective only when implemented early in the chain and with near-perfect consistency. Further, additional treatment components may be required to eliminate all pica attempts.

Adult↗

PubMed2005

Motivational influences on performance maintained by food reinforcement.

In Study 1, we examined the independent effects of reinforcer consumption during sessions and meal consumption prior to sessions on performance maintained by food reinforcement. Nine individuals with developmental disabilities participated. On alternate days, a preferred edible item was delivered during (a) seven sessions conducted before lunch (repeated-reinforcement condition) versus (b) one session each conducted before and after lunch (pre- and postmeal conditions). Results for 7 of 9 participants showed decreased response rates across sessions in the repeated-reinforcement condition; results for 3 of 9 participants showed decreased rates during postmeal relative to premeal conditions. Two participants who did not show a decrement in responding during either comparison participated in Study 2, in which reinforcer consumption during sessions, combined with meal consumption prior to sessions, also had no effect on their performance. In Study 3, we determined whether (a) choice of reinforcers, (b) increased break time between sessions, (c) varied reinforcers, or (d) intermittent reinforcement schedules mitigated the satiation effects observed for the 7 participants in Study 1. Presession choice of reinforcers resulted in maintained performance for 2 of 6 participants exposed to this condition. Varied reinforcement resulted in maintained performance for only 1 of 5 participants exposed to this condition. Neither the increased break between sessions nor the intermittent reinforcement schedule was effective in maintaining performance for the participants who were exposed to these conditions.

Adult↗

PubMed2003

Treatment efficacy of noncontingent reinforcement during brief and extended application.

We evaluated the long-term therapeutic effects of noncontingent reinforcement (NCR). In Experiment 1, NCR effects were examined with 2 participants' arbitrary responses; in Experiment 2, NCR was used as treatment with 3 participants whose self-injurious behavior (SIB) was maintained by automatic reinforcement. In both experiments, NCR consisted of continuous access to a highly preferred leisure item and was implemented initially during 10-min and later during 120-min sessions. Varied reinforcers (leisure items) were subsequently introduced during 120-min sessions to determine if treatment effects might be extended. Finally (Experiment 2 only), NCR was implemented throughout the day in participants' homes. Results of Experiments 1 and 2 showed that reinforcers obtained through object manipulation can compete with those obtained automatically by engaging in SIB during brief NCR sessions. However, data from the 120-min sessions indicated that satiation to a specific leisure item might occur over periods of time more typical of those during which treatment would be implemented. Access to a variety of highly preferred leisure items extended the effectiveness of NCR for some individuals. When NCR was implemented throughout the day (Experiment 2), therapeutic effects were shown to be maintained for up to 1 year.

Adult↗

PubMed2003

Functional analysis of problem behavior: a review.

Functional analysis methodology focuses on the identification of variables that influence the occurrence of problem behavior and has become a hallmark of contemporary approaches to behavioral assessment. In light of the widespread use of pretreatment functional analyses in articles published in this and other journals, we reviewed the literature in an attempt to identify best practices and directions for future research. Studies included in the present review were those in which (a) a pretreatment assessment based on (b) direct observation and measurement of (c) problem behavior was conducted under (d) at least two conditions involving manipulation of an environmental variable in an attempt (e) to demonstrate a relation between the environmental event and behavior. Studies that met the criteria for inclusion were quantified and critically evaluated along a number of dimensions related to subject and setting characteristics, parametric and qualitative characteristics of the methodology, types of assessment conditions, experimental designs, topographies of problem behaviors, and the manner in which data were displayed and analyzed.

Behavior Therapy↗

PubMed2003

Analysis of precurrent skills in solving mathematics story problems.

We conducted an analysis of precurrent skills (responses that increase the effectiveness of a subsequent or "current" behavior in obtaining a reinforcer) to facilitate the solution of arithmetic word (story) problems. Two students with developmental disabilities were taught four precurrent responses (identifying the initial value, change value, operation, and resulting value) in a sequential manner. Results of a multiple baseline design across behaviors showed that the teaching procedures were effective in increasing correct performance of each of the precurrent behaviors with untaught problems during probes and that once the precurrent behaviors were established, the number of correct problem solutions increased.

Adult↗

PubMed2003

The effects of extinction, noncontingent reinforcement and differential reinforcement of other behavior as control procedures.

Several techniques have been used in applied research as controls for the introduction of a reinforcement contingency, including extinction, noncontingent reinforcement (NCR), and differential reinforcement of other behavior (DRO). Little research, however, has examined the relative strengths and limitations of these "reversal" controls. We compared the effects of extinction with those of NCR and DRO in both multi-element and reversal designs, with respect to (a) rate and amount of response decrement, (b) rate of response recovery following reintroduction of reinforcement, and (c) any positive or negative side effects associated with transitions. Results indicated that extinction generally produced the most consistent and rapid reversal effects, with few observed negative side effects.

Adult↗

PubMed2003

Response-restriction analysis: I. Assessment of activity preferences.

We used procedures based on response-restriction (RR) analysis to assess vocational and leisure activity preferences for 3 adults with developmental disabilities. To increase the efficiency of the analysis relative to that reported in previous research, we used criteria that allowed activities to be restricted at the earliest point at which a preference could be determined. Results obtained across two consecutive RR assessments showed some variability in overall preference rankings but a high degree of consistency for highly ranked items. Finally, we compared results of the RR assessment with those of an extended free-operant assessment and found that the RR assessment yielded (a) more differentiated patterns of preference and (b) more complete information about engagement with all of the target activities.

Adult↗

PubMed2003

Effects of reinforcer consumption and magnitude on response rates during noncontingent reinforcement.

Results of previous research on the effects of noncontingent reinforcement (NCR) have been inconsistent when magnitude of reinforcement was manipulated. We attempted to clarify the influence of NCR magnitude by including additional controls. In Study 1, we examined the effects of reinforcer consumption time by comparing the same magnitude of NCR when session time was and was not corrected to account for reinforcer consumption. Lower response rates were observed when session time was not corrected, indicating that reinforcer consumption can suppress response rates. In Study 2, we first selected varying reinforcer magnitudes (small, medium, and large) on the basis of corrected response rates observed during a contingent reinforcement condition and then compared the effects of these magnitudes during NCR. One participant exhibited lower response rates when large-magnitude reinforcers were delivered; the other ceased responding altogether even when small-magnitude reinforcers were delivered. We also compared the effects of the same NCR magnitude (medium) during 10-min and 30-min sessions. Lower response rates were observed during 30-min sessions, indicating that the number of reinforcers consumed across a session can have the same effect as the number consumed per reinforcer delivery. These findings indicate that, even when response rate is corrected to account for reinforcer consumption, larger magnitudes of NCR (defined on either a per-delivery or per-session basis) result in lower response rates than do smaller magnitudes.

Adult↗

PubMed2003

Response-restriction analysis: II. Alteration of activity preferences.

We used response-restriction (RR) assessments to identify the preferences of 7 individuals with mental retardation for a variety of vocational and leisure activities. We subsequently increased their engagement in nonpreferred activities using several procedures: response restriction per se versus a Premack-type contingency (Study 1), supplemental reinforcement for engagement in target activities (Study 2), and noncontingent pairing of reinforcers with nonpreferred activities (Study 3). Results indicated that preferences are not immutable and can be altered through a variety of relatively benign interventions and that the results of RR assessments may be helpful in determining which types of procedures may be most effective on an individual basis.

Adult↗

PubMed2002

Behavioral treatment of self-injury, 1964 to 2000.

A quantitative analysis of behavioral research on the treatment of self-injurious behavior (SIB) over the past 35 years is provided. A literature search covering the period from 1964 to 2000 yielded 396 articles (706 participants) on the treatment of SIB. Most research participants have been male and diagnosed with severe/profound mental retardation. The use of reinforcement-based interventions has increased during the past decade, whereas the use of punishment-based interventions has decreased slightly; both of these trends coincide with the increase in the use of functional assessments. Most treatments have been highly effective in reducing SIB; nevertheless, the disorder persists in spite of an abundance of research, suggesting that a greater emphasis should be placed on prevention.

Adolescent↗

PubMed2002

Duration-based measures of preference for vocational tasks.

We compared results from two preference assessments with data on extended performance of vocational tasks by 4 participants with developmental disabilities. All participants engaged in one task exclusively when seven tasks were available concurrently during a 5-min multiple-stimulus assessment. By contrast, all participants exhibited high levels of engagement in most tasks when the tasks were presented singly for 5 min, and these data showed a high degree of correspondence with those obtained during extended (60-min) vocational assessments.

Adult↗

PubMed2002

Reinforcing efficacy of food on performance during pre- and postmeal sessions.

Assessments were conducted to identify preferred foods for 9 adults with severe to profound mental retardation. Subsequently, the reinforcing effects of each participant's most highly preferred food were evaluated during sessions conducted before and after lunch. Results showed that 4 participants' response rates were higher during premeal sessions than during postmeal sessions. By contrast, pre- and postmeal response rates were indistinguishable for the other 5 participants. These results indicate that the reinforcing efficacy of food may (but does not necessarily) diminish following meals and suggest that the influence of meal schedules should be examined on an individual basis when food is used as reinforcement during training sessions.

Adult↗