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Choosing explanation over performance: Insights from machine learning-based prediction of human intelligence from brain connectivity
A growing body of research predicts individual cognitive ability levels from brain characteristics including functional brain connectivity. The majority of this research achieves statistically significant prediction performance but provides limited insight into neurobiological processes underlying the predicted concepts. The insufficient identification of predictive brain characteristics may present an important factor critically contributing to this constraint. Here, we encourage to design predictive modeling studies with an emphasis on interpretability to enhance our conceptual understanding of human cognition. As an example, we investigated in a preregistered study which functional brain connections successfully predict general, crystallized, and fluid intelligence in a sample of 806 healthy adults (replication: N = 322). The choice of the predicted intelligence component as well as the task during which connectivity was measured proved crucial for better understanding intelligence at the neural level. Further, intelligence could be predicted not solely from one specific set of brain connections, but from various combinations of connections with system-wide locations. Such partially redundant, brain-wide functional connectivity characteristics complement intelligence-relevant connectivity of brain regions proposed by established intelligence theories. In sum, our study showcases how future prediction studies on human cognition can enhance explanatory value by prioritizing a systematic evaluation of predictive brain characteristics over maximizing prediction performance (emphasis added).
According to the capacity account, working memory capacity (WMC) is a causal factor of fluid intelligence (Gf) in that it enables simultaneous activation of multiple relevant information in the aim of reasoning. Consequently, correlation between WMC and Gf should increase as a function of capacity demands of reasoning tasks. Here we systematically review the existing literature on the connection between WMC and Gf. The review reveals conceptual incongruities, a diverse range of analytical approaches, and mixed evidence. While some studies have found a link (e.g., Little et al., 2014), the majority of others did not observe a significant increase in correlation (e.g., Burgoyne et al., 2019; Salthouse, 1993; Unsworth, 2014; Unsworth & Engle, 2005; Wiley et al., 2011). We then test the capacity hypothesis on a much larger, non-Anglo-Saxon culture sample (N = 543). Our WMC measures encompassed Operation, Reading, and Symmetry Span task, whereas Gf was based on items from Raven's Advanced Progressive Matrices (Raven). We could not confirm the capacity hypothesis either when we employed the analytical approach based on the Raven's item difficulty or when the number of rule tokens required to solve a Raven's item was used. Finally, even the use of structural equation modeling (SEM) and its variant, latent growth curve modeling (LGCM), which provide more “process-pure” latent measures of constructs, as well as an opportunity to control for all relevant interrelations among variables, could not produce support for the capacity account. Consequently, we discuss the limitations of the capacity hypothesis in explaining the WMC-Gf relationship, highlighting both theoretical and methodological challenges, particularly the shortcomings of information processing models in accounting for human cognitive abilities.










