Purpose: Children with developmental language disorder (DLD) tend to interpret noncanonical sentences like passives using event probability (EP) information regardless of structure (e.g., by interpreting "The dog was chased by the squirrel" as "The dog chased the squirrel"). Verbs are a major source of EP information in adults…

It is unclear whether children with Down syndrome have differing physical activity and sedentary behavior levels compared to typical children. This study addressed this evidence gap in a national sample. Physical activity/sedentary behavior were ascertained by parental report. Findings highlighted that children with Down syndrome were less likely…

Psychiatric disorders are common in youth with intellectual and developmental disabilities. This is a vulnerable group of children whose behavioural problems often have more complicated care needs than other children, which can place a great deal of stress on their families. However, the association of family mental health issues, level of…

Limited information is available concerning the specificity of the forms and functions of aggressive behavior exhibited by boys with fragile X syndrome (FXS). To investigate these relationships, we conducted indirect functional assessments of aggressive behavior exhibited by 41 adolescent boys with FXS and 59 age and symptom-matched controls with…

Noncompliance with adult instruction is a common problem exhibited by individuals diagnosed with intellectual and developmental disabilities. The high-probability (high-p) request sequence was designed to increase compliance with low-probability (low-p) instructions by rapidly presenting high-p instructions immediately prior to the targeted low-p…

Feeding disorders exhibited by children with developmental disabilities, which include limiting food intake or refusing to consume solid foods, often result in poor health consequences. Interventions for feeding disorders vary in terms of their acceptability to children with disabilities and their families. One specific procedure, the…

Purpose: Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined if individuals with DD are capable of extracting statistical regularities across…

A relationship between motor and mathematical skills has been shown by previous research. However, the question of whether subtypes can be differentiated within developmental coordination disorder (DCD) and/or mathematical learning disability (MLD) remains unresolved. In a sample of children with and without DCD and/or MLD, a data-driven…

This multiple-study experiment evaluated the utility of assessing and treating severe self-injurious behavior (SIB) based on the outcomes of a functional analysis of precursor behavior. In Study 1, a precursor to SIB was identified using descriptive assessment and conditional probability analyses. In Study 2, a functional analysis of precursor…

This methodological review draws attention to the challenges faced by intellectual and developmental disabilities researchers in the appropriate design and analysis of group comparison studies. We provide a brief overview of matching methodologies in the field, emphasizing group-matching designs used in behavioral research on cognition and…

Studies have evaluated a range of interventions to treat food selectivity in children with autism and related developmental disabilities. The high-probability instructional sequence is one intervention with variable results in this area. We evaluated the effectiveness of a high-probability sequence using 3 presentations of a preferred food on…

Noncompliance is one of the most problematic behaviors within the school setting. One strategy to increase compliance of noncompliant students is a high-probability command sequence (HPCS; i.e., a set of simple commands in which an individual is likely to comply immediately prior to the delivery of a command that has a lower probability of…

This paper includes a nontechnical description of methods for calculating effect sizes in intellectual and developmental disability studies. Different hypothetical studies are used to illustrate how null hypothesis significance testing (NHST) and effect size findings can result in quite different outcomes and therefore conflicting results. Whereas…

Dependent variables in research on problem behavior typically are based on measures of response repetition, but these measures may be problematic when behavior poses high risk or when its occurrence terminates a session. We examined response latency as the index of behavior during assessment. In Experiment 1, we compared response rate and latency…

Individuals with intellectual and developmental disabilities often have difficulties foregoing short-term loss for long-term gain. The Iowa Gambling Task (IGT) has been extensively adopted as a laboratory measure of this ability. In the present study, we undertook the first investigation with people with intellectual disabilities using a…