Developmental Perspectives on the Study of Persons with Intellectual Disability.

Developmental approaches provide inclusive, universal, and methodologically rigorous frameworks for studying persons with intellectual disability (ID). This is an exceptionally heterogeneous group with regard to etiology, genotype, and phenotype that simply shares the traditional diagnostic criteria, typically a score of two standard deviations below the population mean of 100 on standardized IQ tests and deficits in adaptive behavior. We trace the foundational, conceptual, and methodological roots of developmental approaches and highlight ways that these and more recent iterations continue to be central to advances in the increasingly nuanced study of persons with ID. This work is premised on the consideration of specific etiological groupings and subgroupings across and between different domains of functioning within the context of familial and complex environments throughout the life span. We highlight the potential contributions of advances in behavioral methodologies, genomics, and neuroscience when considered within universal and hierarchic frameworks based on development.

Attention allocation to facial expressions of emotion among persons with Williams and Down syndromes.

Individuals with Williams syndrome and those with Down syndrome are both characterized by heightened social interest, although the manifestation is not always similar. Using a dot-probe task, we examined one possible source of difference: allocation of attention to facial expressions of emotion. Thirteen individuals with Williams syndrome (mean age = 19.2 years, range = 10-28.6), 20 with Down syndrome (mean age = 18.8 years, range = 12.1-26.3), and 19 typically developing children participated. The groups were matched for mental age (mean = 5.8 years). None of the groups displayed a bias to angry faces. The participants with Williams syndrome showed a selective bias toward happy faces, whereas the participants with Down syndrome behaved similarly to the typically developing participants with no such bias. Homogeneity in the direction of bias was markedly highest in the Williams syndrome group whose bias appeared to result from enhanced attention capture. They appeared to rapidly and selectively allocate attention toward positive facial expressions. The complexity of social approach behavior and the need to explore other aspects of cognition that may be implicated in this behavior in both syndromes is discussed.

Inference From Facial Expressions Among Adolescents and Young Adults With Down Syndrome.

The focus of this study was the ability of adolescents and young adults with Down syndrome to infer meaning from facial expressions in the absence of emotion labels and use this inference in order to adjust their behavior. Participants with Down syndrome ( N = 19, mean nonverbal mental age of 5.8 years) and 4- to 7-year-old typically developing children performed a novel task in which happy and angry faces were provided as feedback for a choice made by the participants. In making a subsequent choice, the participants with Down syndrome performed similarly to the 4 year olds, indicating a difficulty using angry faces as feedback. Individual differences within the group were also apparent. Implications for the development of social competence are discussed.

Voluntary orienting among children and adolescents with Down syndrome and MA-matched typically developing children.

A forced-choice reaction-time (RT) task was used to examine voluntary visual orienting among children and adolescents with trisomy 21 Down syndrome and typically developing children matched at an MA of approximately 5.6 years, an age when the development of orienting abilities reaches optimal adult-like efficiency. Both groups displayed faster reaction times (RTs) when the target location was cued correctly than when cued incorrectly under both short and long SOA conditions, indicating intact orienting among children with Down syndrome. This finding is further evidence that the efficiency of many of the primary components of attention among persons with Down syndrome is consistent with their developmental level.