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Description: In 1984, James Flynn showed evidence for systematically changing intelligence test scores in the USA, demonstrating an increase in average IQ scores from 1932 to 1978 (Flynn, 1984, 1987). This phenomenon has become known as the Flynn Effect. The Flynn effect was replicated in a large number of subsequent studies, although IQ gains appeared to be differentiated according to intelligence domains and investigated countries. On a global scale, gains were typically observed to be larger in fluid than crystallized IQ measures with spatial IQ showing a less unequivocal pattern of gains (Pietschnig & Gittler, 2015; Pietschnig & Voracek, 2015). Although IQ changes were almost invariably positive across most of the 20th century, these gains appeared to be negatively associated with psychometric g (Must et al., 2003; Pietschnig & Voracek, 2015; Rushton, 1999). While IQ increases averaged about 3 points globally per decade in the 1900s, gains appear to have decreased in their strength from around the late 1980s. In fact, some evidence from the late 1990s onwards points towards a stagnation and possibly even a reversal in several countries. For instance, test score decreases have been observed in Scandinavian (Bratsberg & Rogeberg, 2018; Dutton & Lynn, 2013; Sundet et al., 2004; Teasdale & Owen, 2005, 2008) and European countries (Dutton et al., 2016; Dutton & Lynn, 2015; Pietschnig & Voracek, 2015) as well as more recently in the USA (Dworak et al., 2023). To date, the causes of these inconsistent Flynn effect patterns are unclear. One possible reason for the recent inconsistent Flynn effect patterns could be rooted in a so far unobserved domain-specificity of IQ changes. In the past, Flynn effect trajectories have been typically reported in terms of fluid and crystallized intelligence in the sense of Cattell’s intelligence model (Cattell, 1963). This rather crude investigation level may have masked so far only comparatively sparsely documented domain-specific changes. However, the possibility of domain-specificity and consequently ability differentiation as a potential cause for the inconsistent Flynn effect patterns has not been investigated so far. Whether the secular changes on intelligence reflect overall cognitive ability changes (universality) or changes in specific abilities (domain specificity) is an unresolved question with substantial implications. If the Flynn effect occurs on psychometric g (i.e. increases in explained variances in g), the recently observed declines would suggest a deterioration of overall cognitive ability. This would be particularly worrisome as national ability levels have been linked to innovation, technological advancement, economic prosperity, society, and culture (Lynn & Vanhanen, 2002; Pietschnig & Voracek, 2015; Rindermann, 2012). Thus, a decline in ability levels may materialize in a corresponding weakening of these key national economic metrics. In contrast, an ability specialization (i.e. decreases in explained variances in g) would indicate boosted specialized abilities instead of a deterioration of overall cognitive ability. Thus, identifying specialized skills and areas of weakness would provide invaluable insights for educational and vocational policies, training, and interventions. We address this gap in the literature by conducting a cross-temporal investigation on changes in psychometric g based on four representative Austrian standardization samples. A decrease in g and increase in non-g effects (variance unrelated to g) is assumed to reflect cognitive differentiation and specialization at higher ability levels, which boosts specialized abilities (Coyle, 2018). Therefore, by investigating changes in explained variances in g we will be able to clarify whether overall cognitive aptitude (g) is declining or whether they represent a differentiation and specialization of cognitive abilities.