Nathan A. Call
Emory University
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Featured researches published by Nathan A. Call.
ubiquitous computing | 2012
Thomas Plötz; Nils Y. Hammerla; Agata Rozga; Andrea R. Reavis; Nathan A. Call; Gregory D. Abowd
Severe behavior problems of children with developmental disabilities often require intervention by specialists. These specialists rely on direct observation of the behavior, usually in a controlled clinical environment. In this paper, we present a technique for using on-body accelerometers to assist in automated classification of problem behavior during such direct observation. Using simulated data of episodes of severe behavior acted out by trained specialists, we demonstrate how machine learning techniques can be used to segment relevant behavioral episodes from a continuous sensor stream and to classify them into distinct categories of severe behavior (aggression, disruption, and self-injury). We further validate our approach by demonstrating it produces no false positives when applied to a publicly accessible dataset of activities of daily living. Finally, we show promising classification results when our sensing and analysis system is applied to data from a real assessment session conducted with a child exhibiting problem behaviors.
Journal of Applied Behavior Analysis | 2009
Nathan A. Call; Ryan S. Pabico; Joanna E. Lomas
Few direct-assessment procedures are designed to identify potential negative reinforcers (e.g., including demands in the escape condition of functional analyses). Two participants were systematically exposed to a series of demands nominated by caregivers as potential negative reinforcers. Sessions ended following the first instance of problem behavior, and a hierarchy of demand aversiveness was created based on the latency to the first problem behavior. Subsequent functional analyses confirmed the predictive value of the hierarchy, with shorter latency demands consistently producing more differentiated functional analysis outcomes.
Journal of Applied Behavior Analysis | 2012
Amber L. Valentino; M. Alice Shillingsburg; Nathan A. Call
We compared strategies to teach vocal intraverbal responses to an adolescent diagnosed with autism and Down syndrome. One strategy involved echoic prompts only. The second strategy involved an echoic prompt paired with a modeled prompt in the form of sign language. Presenting the modeled prompt with the echoic prompt resulted in faster acquisition of correct responding. Results are discussed in terms of using functional stimulus classes to facilitate vocal intraverbal acquisition with learners who have a history of sign language training.
Journal of Applied Behavior Analysis | 2011
Nathan A. Call; Ryan S. Pabico; Addie J. Findley; Amber L. Valentino
Blocking is a frequent component of treatments for elopement. Unfortunately, blocking may not always be feasible because elopement often occurs when supervision is low or the behavior cannot be prevented. The present study evaluated the use of blocking in the treatment of elopement by using differential reinforcement of other behavior with and without blocking. In this case, results suggested that blocking may be an essential component for differential reinforcement-based treatments of elopement.
Journal of Applied Behavior Analysis | 2012
Nathan A. Call; Nicole M. Trosclair-Lasserre; Addie J. Findley; Andrea R. Reavis; M. Alice Shillingsburg
Research has suggested that a daily multiple-stimulus-without-replacement (MSWO) preference assessment may be more sensitive to changes in preference than other assessment formats, thereby resulting in greater correspondence with reinforcer efficacy over time (DeLeon et al., 2001). However, most prior studies have measured reinforcer efficacy using rate of responding under single-operant arrangements and dense schedules or under concurrent-operants arrangements. An alternative measure of reinforcer efficacy involves the evaluation of responding under progressive-ratio (PR) schedules. In the present study, 7 participants were given a single paired-stimulus (PS) preference assessment followed by daily MSWO preference assessments. After each daily MSWO, participants responded for each stimulus on a PR schedule. The correspondence between break points and preferences, as assessed by the 2 assessment formats, was examined. Results demonstrated that both preference assessments did equally well at predicting reinforcer efficacy, although the PS more consistently identified the most effective reinforcer.
ubiquitous computing | 2012
N. Nazneen; Agata Rozga; Mario Romero; Addie J. Findley; Nathan A. Call; Gregory D. Abowd; Rosa I. Arriaga
Ubiquitous computing has shown promise in applications for health care in the home. In this paper, we focus on a study of how a particular ubicomp capability, selective archiving, can be used to support behavioral health research and practice. Selective archiving technology, which allows the capture of a window of data prior to and after an event, can enable parents of children with autism and related disabilities to record video clips of events leading up to and following an instance of problem behavior. Behavior analysts later view these video clips to perform a functional assessment. In contrast to the current practice of direct observation, a powerful method to gather data about child problem behaviors but costly in terms of human resources and liable to alter behavior in the subjects, selective archiving is cost effective and has the potential to provide rich data with minimal instructions to the natural environment. To assess the effectiveness of parent data collection through selective archiving in the home, we developed a research tool, CRAFT (Continuous Recording And Flagging Technology) and conducted a study by installing CRAFT in eight households of children with developmental disabilities and severe behavior concerns. The results of this study show the promise and remaining challenges for this technology. We have also shown that careful attention to the design of a ubicomp system for use by other domain specialists or non-technical users is key to moving ubicomp research forward.
Research in Developmental Disabilities | 2012
Nathan A. Call; Addie J. Findley; Andrea R. Reavis
It has been suggested that reinforcing problem behavior during functional analyses (FAs) may be unethical (e.g., Carr, 1977), the implication being that doing so may result in an increase in problem behavior outside of FA sessions. The current study assessed whether conducting a FA resulted in increases in problem behavior outside of the FA setting for 4 participants. The rate of problem behavior was measured outside the FA setting prior to and during a FA. Idiosyncratic results suggest that problem behavior outside of the FA setting may increase, decrease, or be unaffected by conducting a FA.
Journal of Applied Behavior Analysis | 2013
Nathan A. Call; M. Alice Shillingsburg; Crystal N. Bowen; Andrea R. Reavis; Addie J. Findley
Qualitative and quantitative differences in social interactions are core symptoms of the autism spectrum disorder (ASD) diagnostic criteria, although there is heterogeneity among individuals with ASDs. This study used a concurrent operants arrangement to evaluate whether social interactions functioned as positive reinforcement, negative reinforcement, or as neutral stimuli for 6 individuals with autism. Data suggest that clinicians who work with individuals with ASD should ascertain the functional properties of social interactions prior to using them as a consequence in interventions.
Behavior Modification | 2011
Amber L. Valentino; M. Alice Shillingsburg; Nathan A. Call; Britney Burton; Crystal N. Bowen
Children with autism have significant communication delays. Although some children develop vocalizations through shaping and differential reinforcement, others rarely exhibit vocalizations, and alternative methods are targeted in intervention. However, vocal language often remains a goal for caregivers and clinicians. Thus, strategies to increase frequency of vocalizations are needed. In the present study, the authors examined the effect of extinction of previously acquired signed mands on vocalizations in three children diagnosed with autism. Experiment 1 examined the effects of differential reinforcement of vocalizations and extinction of signed mands combined. In Experiment 1, it was unknown whether the reinforcement of vocalizations alone could have produced the effects; therefore, Experiment 2 isolated the effects of reinforcement and extinction by reinforcing vocalizations in baseline. An increase in rate of vocalizations occurred following the application of extinction of signed mands and differential reinforcement of vocalizations in Experiment 1 and following extinction of signed mands in Experiment 2.
Acta de Investigación Psicológica | 2014
Jessica P. Álvarez; Nathan A. Call; Joanna Lomas Mevers
Functional assessment, and function-based treatments, are the gold standard for the treatment of problem behavior. Historically, these assessment and treatment evaluations have been conducted in austere clinical settings to increase internal validity. While prioritizing internal validity is critical in the initial stages of a treatment evaluation, if there is not an eventual shift to prioritizing the external or social validity of the treatment it may inevitably fail in the natural environment. The purpose of this case example is to outline a socially valid approach to the assessment and treatment of problem behavior that ensures individuals’ and their families’ lives benefit in meaningful ways. More specifically, this case-example will outline a method of prioritizing social validity to identify treatment goals, conduct functional analysis, evaluate and generalize treatment, and implement caregiver training.