2017; 02(05): 104-115 psy/17/1720/gmj

Original Research Article

Crystallized and Fluid Intelligence of Adolescents and Adults with Intellectual Disability and with Typical Development: Impaired, Stable or Compensatory Trajectories?

Irit Chen1, Hefziba Lifshitz2 & Eli Vakil3.
1Efrata College of Education, Jerusalem, Israel
2Special Education Department, Machado Chair for Research on Cognitive Modifiability and Human Development, School of Education, Bar-Ilan University, Israel
3Department of Psychology and Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel

Correspondence to
Hefziba Lifshitz, Special Education Department, Machado Chair for Research on Cognitive Modifiability and Human Development, School of Education, Bar-Ilan University, Israel

First Published Online 29 june 2017

ABSTRACT

Three possible of cognitive trajectories in the population with ID (Fisher & Zeaman, 1970; Lifshitz-Vahav, 2015) through the life span compared to the cognitive trajectory of the Typical developed (TD) population (Kauffman, 2001; Wechsler, 1945) were proposed. The "Impaired Trajectory", stable and "Continues Trajectories. This study's goal was to examine Crystallized and fluid intelligence trajectories in individuals with non-specific ID (IQ=40-70) compared to individuals with typical development in four age cohorts: young adolescence (10-16), older adolescence (16-21), young adulthood (23-29) and adults (30-40). Method: Participants were individuals with mild to moderate NSID (N=102, IQ=50-70), who were compared to individuals with TD (N=102, IQ=85-115) in four age groups (10-16, 17-21, 23-29, 31-40). Crystalized Intelligence was examined by vocabulary and similarities (Wechsler battery, 1997b, 2010), and fluid intelligence was examined by the Raven Matrices (1983), Verbal fluency (Kavé, 2005), and Block design (Wechsler). Results: vocabulary and similarities revealed a parallel continues trajectory from 21 to 40. Semantic fluency peaked at the 21 among the TD population and at their 40 in the ID population. phonemic fluency and the Raven revealed also parallel continues trajectory from 21-40 for both groups. Block design revealed in the TD group indicate a decline from older adolescents to adulthood (40-17) whereas ID group revealed continues trajectory from 21 to 40. Conclusions: Our findings support the Compensation Age Theory (Lifshitz-Vahav, 2015) regarding the contribution of chronological age to the cognitive ability of individuals with ID. Furthermore, adults with ID can benefit not only from mediated learning experience but from direct exposure to the stimulus.

Keywords: Crystallized and Fluid intelligence; individuals with ID; impaired, stable, continuous trajectories.

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