Evaluation of the Double-Deficit Hypothesis in College Students Referred for Learning Difficulties

Abstract

The present study explored the double-deficit hypothesis (DDH) in a sample of 146 college students with and without reading disabilities (RD). The results indicated that although both phonological awareness (PA) and visual naming speed (VNS) contributed to performance on measures of decoding and comprehension, their relative contribution was influenced both by the nature of the stimulus (word vs. nonword vs. text) and by the conditions of the task (timed vs. untimed). Similar results were obtained using an individual differences approach, or when between-group comparisons were made of individuals with deficits in PA or VNS. The relative representation of DDH subgroups in groups of adults with RD varied based on the classification criteria used to define RD. These results support the DDH, extend its applicability to adults, and have implications for diagnostic decision making.

Examination of the double-deficit hypothesis with adolescents and young adults with dyslexia

“…As is consistent with previous research (e.g., Cirino et al, 2005;Wolf et al, 2002), a standard score cutoff of ≤85 was used to establish the groups. Participants scoring at or below this cutoff on CTOPP PAC and RNC were assigned to the DD subtype.…”

“…The first, which is the score derived from the norms and scoring procedures of the NDRT, indicates the examinee's timed reading comprehension skills, as the examinee is asked to answer as many of the 38 multiple-choice questions after reading as many of seven passages within a 20-min time limit. The second is a metric created by Cirino et al (2005) and provides an estimate of untimed reading comprehension skills by calculating the percentage of correctly answered items that were responded to within the time limit. This score is calculated by dividing the number of correct items by the number of attempted items.…”

“…This score is calculated by dividing the number of correct items by the number of attempted items. Information on its psychometric properties was not provided by Cirino et al (2005).…”

“…Because of the established relationship between NS and ADHD, concern has been raised that attentional deficits have not been controlled in samples used to investigate the DDH (Semrud-Clikeman et al, 2000). The samples of extant empirical studies have tended to be unclear regarding the presence of ADHD or included individuals with comorbid ADHD (e.g., Ackerman et al, 2001;Cirino et al, 2005;Katzir et al, 2008;Wolf et al, 2002). Without controlling for ADHD and other disorders with associated NS difficulties, it is generally unknown whether NS difficulties are largely due to dyslexia.…”

“…It should also be noted that some of the assumptions of the DDH can be examined without dichotomizing continuous variables (e.g., with a multiple regression approach), whereas others must be examined with a between-group approach after dichotomizing the continuous variables to form the DDH subtypes. Both approaches are recommended and are valuable in examinations of the DDH (Cirino et al, 2005), and therefore, both approaches are used in the current study.…”