The prediction of nonverbal intelligence by language and executive functions

The purpose of this study was to investigate the predictive relationship between nonverbal intellectual functioning, language, and executive functioning in a sample of non-referred college students. Participants included 51 undergraduate college students (17 male, 34 female) enrolled in psychology courses at a Midwestern university. Nonverbal intellectual functioning was assessed using the Leiter International Performance Scale, Third Edition (Leiter-3; Roid, Miler, Pomplun, & Koch, 2013), specifically the Figure Ground, Form Completion, Classifications/Analogies, and Sequential Order subtests, as well as the Nonverbal IQ composite. The Peabody Picture Vocabulary Test, Fifth Edition (PPVT-5; Dunn, 2019) and Expressive Vocabulary Test, Third Edition (EVT-3; Williams, 2019) were administered to assess receptive and expressive language skills, respectively. Executive functioning was assessed using the Delis- Kaplan Executive Function System (D-KEFS; Delis, Kaplan, & Kramer, 2001), specifically the Verbal Fluency, Color-Word Interference, and Trail Making Test subtests. The multiple regression showed receptive language was the only predictor of Nonverbal IQ. The multivariate regression showed receptive language was the only predictor of the Leiter subtests, specifically, mental flexibility and nonverbal reasoning. The current results include considerations for clinicians evaluating patients with various language and executive functioning deficits.Thesis (Ph. D.