Assessment of impulsivity and the development of self-control in students with attention deficit hyperactivity disorder.

We examined a combined approach of manipulating reinforcer dimensions and delay fading to promote the development of self‐control with 3 students diagnosed with attention deficit hyperactivity disorder. First, we administered a brief computer‐based assessment to determine the relative influence of reinforcer rate (R), reinforcer quality (Q), reinforcer immediacy (I), and effort (E) on the students' choices between concurrently presented math problems. During each session, one of these dimensions was placed in direct competition with another dimension (e.g., RvI involving math problem alternatives associated with high‐rate delayed reinforcement vs. low‐rate immediate reinforcement), with all possible pairs of dimensions presented across the six assessment conditions (RvQ, RvI, RvE, QvI, QvE, IvE). The assessment revealed that the choices of all 3 students were most influenced by immediacy of reinforcement, reflecting impulsivity. We then implemented a self‐control training procedure in which reinforcer immediacy competed with another influential dimension (RvI or QvI), and the delay associated with the higher rate or quality reinforcer alternative was progressively increased. The students allocated the majority of their time to the math problem alternatives yielding more frequent (high‐rate) or preferred (high‐quality) reinforcement despite delays of up to 24 hr. Subsequent readministration of portions of the assessment showed that self‐control transferred across untrained dimensions of reinforcement.     

Evaluation of pharmacological treatment of impulsivity in children with attention deficit hyperactivity disorder

We used an assessment that involved competing reinforcer dimensions in a concurrent-schedules arrangement to examine the effects of stimulant medication on impulsivity (i.e., sensitivity of choices to reinforcer immediacy relative to rate, quality, and effort) with 4 students with attention deficit hyperactivity disorder. The assessments were administered in the context of a double-blind, placebo-controlled, counterbalanced reversal design. Reinforcer immediacy was the most influential dimension for 3 of the students and the second most influential dimension for 1 of the students across placebo and medication conditions; medication did not affect these sensitivities.     

A Brief Experimental Analysis of Reinforcer and Response Dimensions Related to Self-Control in an Outpatient Clinic

We conducted an assessment of self-control and impulsivity with 9 children referred to an outpatient clinic for impulsive, inattentive, and hyperactive behaviors. Each condition of the assessment consisted of a choice between 2 concurrently presented math or writing tasks, with 1 alternative reflecting impulsive responding and 1 alternative reflecting self-control. For the participants who demonstrated impulsive responding in 1 of 2 baseline conditions, we systematically varied reinforcer quality, delay to reinforcement, and response effort to evaluate the effects of these dimensions on the participants’ choices. Results of the assessment revealed that 3 participants displayed self-control responding, and 6 participants displayed impulsive responding during baseline conditions. Of the participants who displayed initial impulsivity, all showed self-control when 1 or more response or reinforcement dimensions were modified to bias responding within a brief multielement design. Results provide a unique application of concurrent schedules for conducting a brief assessment of impulsive responding in an outpatient clinical setting.     

Assessing factors that influence young children's food preferences and choices

Researchers have identified an unbalanced diet as a key risk factor in the etiology of many chronic diseases (World Health Organization, 2003 ). Although researchers have found that numerous factors influence children's food choices, no assessment exists to identify these factors. In Experiment 1, we established preliminary empirical evidence of children's preferences for healthier and less‐healthy foods, and found that 16 of 21 children preferred less‐healthy foods to healthier foods. In Experiment 2, we established the utility of an analogue, competing parameters assessment designed to approximate children's food choices in the natural environment. We identified either quality or immediacy as the most influential parameters governing four of four childrens' food choices. We found that effort influenced the efficacy of these reinforcer parameters in a predictable manner for one of four children.     

ASSESSING INFLUENTIAL DIMENSIONS OF REINFORCERS ON CHOICE IN STUDENTS WITH SERIOUS EMOTIONAL DISTURBANCE

We examined how reinforcer rate, quality, delay, and response effort combined to influence the choices of 6 youths with learning and behavior difficulties, and the viability of an assessment methodology derived from matching theory for determining differential responsiveness to those reinforcer and response dimensions. The students were given two concurrent sets of math problems that were equal on two dimensions but competed on two other dimensions (e.g., one set yielded higher rate and lower quality reinforcement than the other). Competing dimensions were counterbalanced across the six conditions of the initial assessment phase, permitting assessment of each dimension on time allocation. The conditions resulting in the most and least time allocated to one problem set alternative relative to the other were then replicated. Time allocated to each of the problems within sets was differentially affected by the reinforcer and/or response dimensions, with allocation patterns varying across students. The results are discussed in the context of implications for the design of treatments and extrapolations from basic research on matching and behavioral economics.     

A brief computer-based assessment of reinforcer dimensions affecting choice

In an extension of Neef, Shade, and Miller (1994), we used a brief computer-based assessment of differential responsiveness to reinforcer rate, quality, delay, and response effort in affecting the choices of 11 participants. The assessment involved successive presentations of two concurrent sets of math problems, each set associated with competing reinforcer or response dimensions in a counterbalanced fashion. The results showed that the reinforcer and response dimensions differentially affected choice, with time-allocation patterns varying across students.     

IMPULSIVITY IN STUDENTS WITH SERIOUS EMOTIONAL DISTURBANCE: THE INTERACTIVE EFFECTS OF REINFORCER RATE,DELAY, AND QUALITY

We conducted two studies extending basic matching research on self-control and impulsivity to the investigation of choices of students diagnosed as seriously emotionally disturbed. In Study 1 we examined the interaction between unequal rates of reinforcement and equal versus unequal delays to reinforcer access on performance of concurrently available sets of math problems. The results of a reversal design showed that when delays to reinforcer access were the same for both response alternatives, the time allocated to each was approximately proportional to obtained reinforcement. When the delays to reinforcer access differed between the response alternatives, there was a bias toward the response alternative and schedule with the lower delays, suggesting impulsivity (i.e., immediate reinforcer access overrode the effects of rate of reinforcement). In Study 2 we examined the interactive effects of reinforcer rate, quality, and delay. Conditions involving delayed access to the high-quality reinforcers on the rich schedule (with immediate access to low-quality reinforcers earned on the lean schedule) were alternated with immediate access to low-quality reinforcers on the rich schedule (with delayed access to high-quality reinforcers on the lean schedule) using a reversal design. With 1 student, reinforcer quality overrode the effects of both reinforcer rate and delay to reinforcer access. The other student tended to respond exclusively to the alternative associated with immediate access to reinforcers. The studies demonstrate a methodology based on matching theory for determining influential dimensions of reinforcers governing individuals' choices.     

The Effects of Childhood ADHD Symptoms on Early-onset Substance Use: A Swedish Twin Study

Research has documented that children and adolescents with attention-deficit/hyperactivity disorder (ADHD) are at increased risk of substance use problems. Few studies, however, have focused on early-onset substance use. This study therefore investigated how the two symptom dimensions of ADHD (hyperactivity/impulsivity and inattention) are associated with early-onset substance use, the role of persistent ADHD for the association, and to what extent the association is influenced by genetic and environmental factors. Twins (1,480 pairs) in the Swedish Twin Study of Child and Adolescent Development were followed from childhood to adolescence. ADHD symptoms were measured at age 8–9 and age 13–14 via parent-report, whereas substance use was assessed at age 13–14 via self-report. Results revealed that hyperactive/impulsive symptoms predicted early-onset “sometimes” tobacco use (adjusted odds ratios, 1.12, for one symptom count), controlling for inattentive symptoms and conduct problem behaviors. There is no independent effect of inattentive symptoms on early-onset substance use. Children with persistent hyperactivity/impulsivity (defined as scoring above the 75th percentile at both time points) had a pronounced risk of both early-onset tobacco and alcohol use (adjusted odds ratios from 1.86 to 3.35, compared to the reference group). The associations between hyperactivity/impulsivity and early-onset substance use were primarily influenced by genetic factors. Our results indicated that hyperactivity/impulsivity, but not inattention, is an important early predictor for early-onset substance use, and a shared genetic susceptibility is suggested to explain this association.     

Independence of terminal-link entry rate and immediacy in concurrent chains

In Phase 1, 4 pigeons were trained on a three-component multiple concurrent-chains procedure in which components differed only in terms of relative terminal-link entry rate. The terminal links were variable-interval schedules and were varied across four conditions to produce immediacy ratios of 4:1, 1:4, 2:1, and 1:2. Relative terminal-link entry rate and relative immediacy had additive and independent effects on initial-link response allocation, and the data were well-described by a generalized-matching model. Regression analyses showed that allowing sensitivity to immediacy to vary across components produced only trivial increases in variance accounted for. Phase 2 used a three-component concurrent-schedules procedure in which the schedules were the same as the initial links of Phase 1. Across two conditions, the relative reinforcer magnitude was varied. Sensitivity to relative reinforcer rate was independent of relative magnitude, confirming results of prior studies. Sensitivity to relative reinforcer rate in Phase 2 did not vary systematically across subjects compared to sensitivity to relative entry rate in Phase 1, and regression analyses confirmed again that only small increases in variance accounted for were obtained when sensitivities were estimated independently compared with a single estimate for both phases. Overall, the data suggest that conditioned and primary reinforcers have functionally equivalent effects on choice and support the independence of relative terminal-link entry rate and immediacy as determiners of response allocation. These results are consistent with current models for concurrent chains, including Grace's (1994) contextual choice model and Mazur's (2001) hyperbolic value-added model.     

A multitrait-multisource confirmatory factor analytic approach to the construct validity of ADHD rating scales

Confirmatory factor analysis was used to model a multitrait-multisource design to evaluate the construct validity of attention-deficit/hyperactivity disorder (ADHD) rating scales. The 2 trait factors were the ADHD inattention and hyperactivity/impulsivity dimensions. The 2 source factors were parents and teachers. In Study 1, parents and teachers rated 1,475 Australian elementary school children on the ADHD symptoms. In Study 2, parents and teachers rated 285 Brazilian elementary school children on the ADHD symptoms. Similar results occurred in both studies with most of the ADHD symptoms containing more source than trait variance, thus providing weak evidence for the convergent and discriminant validity of the symptoms as measured by rating scales. The study outlines the implications of such strong source effects for understanding ADHD.     

The Role of Maternal and Child ADHD Symptoms in Shaping Interpersonal Relationships

The current study investigated the influence of maternal ADHD symptoms on: (a) mothers’ own social functioning; (b) their child’s social functioning; and (c) parent–child interactions following a lab-based playgroup involving children and their peers. Participants were 103 biological mothers of children ages 6–10. Approximately half of the children had ADHD, and the remainder were comparison youth. After statistical control of children’s ADHD diagnostic status and mothers’ educational attainment, mothers’ own inattentive ADHD symptoms predicted poorer self-reported social skills. Children with ADHD were reported to have more social problems by parents and teachers, as well as received fewer positive sociometric nominations from playgroup peers relative to children without ADHD. After control of child ADHD status, higher maternal inattention and hyperactivity/impulsivity each predicted children having more parent-reported social problems; maternal inattention predicted children receiving more negative sociometric nominations from playgroup peers. There were interactions between maternal ADHD symptoms and children’s ADHD diagnostic status in predicting some child behaviors and parent–child relationship measures. Specifically, maternal inattention was associated with decreased prosocial behavior for children without ADHD, but did not influence the prosocial behavior of children with ADHD. Maternal inattention was associated with mothers’ decreased corrective feedback and, at a trend level, decreased irritability toward their children with ADHD, but there was no relationship between maternal inattention and maternal behaviors for children without ADHD. A similar pattern was observed for maternal hyperactivity/impulsivity and mothers’ observed irritability towards their children. Treatment implications of findings are discussed.     

An analysis of choice making in the assessment of young children with severe behavior problems

We examined how positive and negative reinforcement influenced time allocation, occurrence of problem behavior, and completion of parent instructions during a concurrent choice assessment with 2 preschool-aged children who displayed severe problem behavior in their homes. The children were given a series of concurrent choice options that varied availability of parent attention, access to preferred toys, and presentation of parent instructions. The results showed that both children consistently allocated their time to choice areas that included parent attention when no instructions were presented. When parent attention choice areas included the presentation of instructions, the children displayed differential patterns of behavior that appeared to be influenced by the presence or absence of preferred toys. The results extended previous applications of reinforcer assessment procedures by analyzing the relative influence of both positive and negative reinforcement within a concurrent-operants paradigm.     

Familial Aggregation of ADHD Characteristics

Patterns of familial aggregation of ADHD symptoms in parents of ADHD and non-ADHD children were examined. Within the ADHD sample, symptom aggregation was examined as a function of biological relationship, parent and child gender, and children's comorbid diagnoses. Participants consisted of parents of 579 children with ADHD, Combined Type participating in the multimodal treatment study of children with ADHD and parents of 288 normal control participants. Adult symptoms of ADHD were measured by both self-report and report of a significant other. Results indicated that the parents of children with ADHD had higher ratings of inattention/cognitive problems, hyperactivity/restlessness, impulsivity/emotional lability, and lower self-concept than parents of children without ADHD on both self-report and other-report ratings. Within the ADHD sample of children, other-report ratings of inattention/cognitive problems and impulsivity/emotional lability were higher for biological parents compared to nonbiological parents whereas self-ratings were not related to biological status. These findings support previous research documenting familial aggregation of ADHD and appear to strengthen the hypothesis that there is a genetic contribution to ADHD.     

Impulsivity and Attention Deficit-Hyperactivity Disorder: Subtype Classification Using the UPPS Impulsive Behavior Scale

This study examined the classification accuracy of the UPPS Impulsive Behavior Scale (UPPS) in discriminating several attention deficit/hyperactivity disorder (ADHD) subtypes, including predominantly inattentive type (ADHD/I), combined type (ADHD/C), and combined type with behavioral problems (ADHD/ODD), between each other and a non-ADHD control group using logistic regression analyses. The sample consisted of 88 children ranging in age from 9.0 years to 12.8 years, with a mean of 10.9 years. Children were predominantly male (74%) and Caucasian (86%) and in grades 3–7. Results indicated that the UPPS performed well in classifying ADHD subtypes relative to traditional diagnostic measures. In addition, analyses indicated that differences in symptoms between subtypes can be explained by specific pathways to impulsivity. Implications for the assessment of ADHD and conceptual issues are discussed.     

Determinants of pigeons' choices in token-based self-control procedures

Four pigeons were exposed to a token-based self-control procedure with stimulus lights serving as token reinforcers. Smaller-reinforcer choices produced one token immediately; larger-reinforcer choices produced three tokens following a delay. Each token could be exchanged for 2-s access to food during a signaled exchange period each trial. The main variables of interest were the exchange delays (delays from the choice to the exchange stimulus) and the food delays (also timed from the choice), which were varied separately and together across blocks of sessions. When exchange delays and food delays were shorter following smaller-reinforcer choices, strong preference for the smaller reinforcer was observed. When exchange delays and food delays were equal for both options, strong preference for the larger reinforcer was observed. When food delays were equal for both options but exchange delays were shorter for smaller-reinforcer choices, preference for the larger reinforcer generally was less extreme than under conditions in which both exchange and food delays were equal. When exchange delays were equal for both options but food delays were shorter for smaller-reinforcer choices, preference for the smaller reinforcer generally was less extreme than under conditions in which both exchange and food delays favored smaller-reinforcer choices. On the whole, the results were consistent with prior research on token-based self-control procedures in showing that choices are governed by reinforcer immediacy when exchange and food delays are unequal and by reinforcer amount when exchange and food delays are equal. Further, by decoupling the exchange delays from food delays, the results tentatively support a role for the exchange stimulus as a conditioned reinforcer.     

Zebrafish choice behavior is sensitive to reinforcer rate,immediacy, and magnitude ratios

Behavioral flexibility has, in part, been defined by choice behavior changing as a function of changes in reinforcer payoffs. We examined whether the generalized matching law quantitatively described changes in choice behavior in zebrafish when relative reinforcer rates, delays/immediacy, and magnitudes changed between two alternatives across conditions. Choice was sensitive to each of the three reinforcer properties. Sensitivity estimates to changes in relative reinforcer rates were greater when 2 variable-interval schedules were arranged independently between alternatives (Experiment 1a) than when a single schedule pseudorandomly arranged reinforcers between alternatives (Experiment 1b). Sensitivity estimates for changes in relative reinforcer immediacy (Experiment 2) and magnitude (Experiment 3) were similar but lower than estimates for reinforcer rates. These differences in sensitivity estimates are consistent with studies examining other species, suggesting flexibility in zebrafish choice behavior in the face of changes in payoff as described by the generalized matching law.     

An evaluation of stimulant medication on the reinforcing effects of play

Although a vast literature has indicated that stimulant medications are effective for reducing inappropriate behavior in children with attention deficit hyperactivity disorder (ADHD), the effects of stimulant medication on ancillary behaviors (e.g., play) have yet to be investigated with the same rigor. We used a reinforcer assessment procedure to evaluate the effects of medication on the play and social behavior of 5 preschool children who had been diagnosed with ADHD. Conditions included (a) social reinforcement (i.e., playing with friends), (b) alone play, and (c) quiet time (i.e., resting). Results indicated that 1 of the 5 participants selected fewer social reinforcers and more nonsocial reinforcers (alone play or quiet time) while on medication. The findings indicate that the reinforcer assessment procedure may be a viable way to evaluate medication effects on an ongoing basis and to inform treatment decisions.     

Evidence for a General ADHD Factor from a Longitudinal General School Population Study

Recent factor analytic studies in Attention-Deficit/Hyperactivity Disorder (ADHD) have shown that hierarchical models provide a better fit of ADHD symptoms than correlated models. A hierarchical model includes a general ADHD factor and specific factors for inattention, and hyperactivity/impulsivity. The aim of this 12-month longitudinal study was to test the generalizability of the hierarchical models of ADHD within an elementary school population of 6–9 year old children (250 boys, 260 girls). Examination of differences as a function of informant (parent vs. teacher ratings), sex, and time was conducted. Six potential factor structures for the 18 items of the SWAN (Strengths and Weaknesses of ADHD-symptoms and Normal-behavior) scale were tested using confirmatory and exploratory factor analyses. Hierarchical models with a general ADHD factor and two or three specific factors best accounted for parent and teacher reports of symptoms for both boys and girls and at two time points separated by a 12-month interval. Findings indicate that the 18 SWAN items measure a common latent trait as well as orthogonal factors or dimensions of inattention and hyperactivity/impulsivity.     

Context influences decision-making in boys with attention-deficit/hyperactivity disorder: A comparison of traditional and novel choice-impulsivity paradigms

Attention-deficit/hyperactivity disorder (ADHD) is characterized by an impaired ability to maintain attention and/or hyperactivity/impulsivity. Impulsivity is frequently defined as the preference for small, immediate rewards over larger, delayed rewards, and has been associated with a variety of negative outcomes such as risky behavior and academic difficulty. Extant studies have uniformly utilized the traditional paradigm of presenting two response choices, which limits the generalization of findings to scenarios in which children/adolescents are faced with dichotomous decisions. The current study is the first to examine the effect of manipulating the number of available response options on impulsive decision-making in boys with and without ADHD. A total of 39 boys (ADHD = 16, typically developing [TD] = 23) aged 8–12 years completed a traditional two-choice impulsivity task and a novel five-choice impulsivity task to examine the effect of manipulating the number of choice responses (two vs five) on impulsive decision-making. A five-choice task was utilized as it presents a more continuous array of choice options when compared to the typical two-choice task, and is comparable given its methodological similarity to the two-choice task. Results suggested that boys with ADHD were significantly more impulsive than TD boys during the two-choice task, but not during the five-choice task. Collectively, these findings suggest that ADHD-related impulsivity is not ubiquitous, but rather dependent on variation in demands and/or context. Further, these findings highlight the importance of examining ADHD-related decision-making within the context of alternative paradigms, as the exclusive utilization of two-choice tasks may promote inaccurate conceptualizations of the disorder.     

Rapid acquisition of preference in concurrent chains when alternatives differ on multiple dimensions of reinforcement

Pigeons responded in a concurrent-chains procedure in which terminal-link reinforcer variables were changed unpredictably across sessions. In Experiment 1, the terminal-link schedules were fixed-interval (FI) 8 s and FI 16 s, and the reinforcer magnitudes were 2 s and 4 s. In Experiment 2 the probability of reinforcement (100% or 50%) was varied with immediacy and magnitude. Multiple-regression analyses showed that pigeons' initial-link response allocation was determined by current-session reinforcer variables, similar to previous studies which have varied only immediacy (Grace, Bragason, & McLean, 2003). Sensitivity coefficients were positive and statistically significant for all reinforcer variables in both experiments. Analyses of responding within individual sessions showed that final levels of preference for dominated sessions, in which all reinforcer variables favored the same terminal link, were more extreme than for tradeoff sessions in which at least one reinforcer variable favored each alternative. This result implies that response allocation was determined by multiple reinforcer variables within individual sessions, consistent with the concatenated matching law. However, in Experiment 2, there was a nonlinear (sigmoidal) relationship between response allocation and relative value, which suggests the possibility that reinforcer variables may interact during acquisition, contrary to the matching law.