The predictive power of intelligence: Miranda abilities of individuals with intellectual disability

The Miranda v. Arizona (1966) decision was intended to protect individuals' rights in custodial situations. The purpose of this paper was to evaluate Miranda abilities of individuals with intellectual disability and evaluate the utility of intelligence in predicting these abilities. Additionally, we aimed to provide an updated resource for forensic examiners regarding the performance of individuals with intellectual disability on the Standardized Assessment of Miranda Abilities (SAMA).

We hypothesized that IQ, particularly verbal intelligence and working memory, would significantly predict abilities related to recall, vocabulary, knowledge, and acquiescence in a sample with intellectual disability.

Sixty-two individuals diagnosed with intellectual disability completed the Wechsler Adult Intelligence Scale-4th ed. (WAIS-IV), the SAMA, and a background questionnaire.

Participants demonstrated significantly worse Miranda abilities when compared to the normative sample of the SAMA apart from acquiescence, which they demonstrated at significantly higher rates. Participants exhibited limited existing knowledge of Miranda rights and showed minimal improvement following exposure to a Miranda warning. Verbal abilities were a significant predictor of recall and vocabulary abilities with large effect sizes on average (i.e., ds > 1). IQ was not predictive of misconceptions about Miranda or acquiescence.

Verbal intelligence was an important contributor to understanding Miranda. This study provided data related to performance on the SAMA by a sample of individuals with intellectual disability. It may serve as a reference for evaluators, legal professionals, and law enforcement officers when working with justice-involved persons with suspected intellectual disability. (PsycINFO Database Record (c) 2020 APA, all rights reserved).