Prevalence of low scores and discrepancy of results on intelligence measure (WAIS-IV) in adults

Wechsler Adult Intelligence Scale is one of the world’s most recognizable measures of intelligence for adults, comprised of 10 core and 5 supplemental subtests. Since it is a battery of tests, research of discrepancy between subtest scores enables conclusions regarding possible misinterpretations of a single test score. Adaptation and standardization of the fourth revision of WAIS was conducted in 2019. for Croatian language. The aim of the study was to examine the prevalence of low scores on subtests and Indexes as well as the difference between scores regarding overall intelligence level. Data was gathered for 700 adults (343 males and 357 females), aged between 16 and 74 years. The sample was stratified according to age, self-reported gender (male/female), and five geographical regions. The results show that single low scores among healthy adults are not uncommon, even when using strict and rigorous cut-off scores such as below 2nd percentile (i. e. 12.9 for subtests and 5.7 for Index scores). Also, results show that 1 out of 4 participants of the study had differences between Index scores greater than one standard deviation, and those differences were greater and more common in groups with above average and high overall intelligence. These results indicate that variability of results is a normal feature of cognitive functioning and should not automatically be considered as proof of existence of a cognitive disorder.