DOI: 10.60641/1xhz-0h83
title: Wechsler Adult Intelligence Scale (WAIS)

description: The Netherlands Twin Register (NTR) consists of individuals who have agreed to participate in twin-family studies and was established and is managed by the Department of Biological Psychology, VU University Amsterdam (see: https://tweelingenregister.vu.nl/). The NTR was established in 1987 and has enrolled around 120.000 twins and a roughly equal number of their relatives. The majority of twin families have participated one or more times in survey studies on a host of epidemiological variables including social demography, personality, lifestyle, somatic and mental health, and subsamples took part in biomaterial collection (e.g. DNA) and dedicated projects for e.g. neuropsychological, biomarker, and behavioral traits. The recruitment into the NTR is fully inclusive without any restrictions on enrolment. The NTR is committed to actively seek the commitment of its participants to science and their continued involvement in NTR research by maintaining a website, electronic newsletters, and the MijnNTR portal that provides personalized feedback to participants. The NTR resources, e.g. the longitudinal phenotyping, the extended pedigree structures, and the multi-generation genotyping allow for future twin-family research that will contribute to gene discovery, causality modelling, and studies of genetic and cultural inheritance of behavioral traits and mental and physical health. In the CID data catalogue, only the NTR projects for children and adolescents (<18 years of age) have been included. This is refered to as the Young Netherlands Twin Register (YNTR). 
description: The Wechsler Adult Intelligence Scale (WAIS) is an IQ test designed to measure intelligence and cognitive ability in adults and older adolescents. Most versions contain sub tests that represent the following components of intelligence: Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), Processing Speed Index (PSI). Two broad scores, which can be used to summarize general intellectual ability, can also be derived: 1) the Full Scale IQ (based on the total combined performance of the VCI, PRI, WMI, and the PSI) and 2) the General Ability Index (based only on the six subtests that the VCI and PRI comprise).
description: In NTR project YC_BS3, a selection of subtests of the WAIS-II (Wechsler, 1997) was administered: Vocabulary, Block Design, Similarities and Matrix Reasoning. Raw test scores were standardized based on the age of the participant. Then, a correction for the number of excluded subtests was performed to be able to calculate IQ scores: the sum of the standardized score of Vocabulary and Similarities was multiplied by 2.5 (verbal IQ), the sum of standardized scores of Block Design and Matrix Reasoning was multiplied by 3 (performance IQ), the sum of verbal and performance IQ (total IQ). In NTR project YE_COG18, participants of 16 years of age or above completed 11 subtests of the Dutch WAIS-III (Wechsler, 1997). Verbal and nonverbal intelligence scores were calculated as the mean subtest score on the 6 verbal, respectively the 5 nonverbal subtests, the scores were standardized for the appropriate age group, based on a population sample of same-aged subjects in the Netherlands. Standardization norms were the same across the sexes.