Searching for replicable associations between cortical thickness and psychometric variables in healthy adults: empirical facts.

The study of associations between inter-individual differences in brain structure and behaviour has a long history in psychology and neuroscience. Many associations between psychometric data, particularly intelligence and personality measures and local variations of brain cortical thickness (CT) have been reported. While the impact of such findings often go beyond scientific communities, resonating in the public mind, their replicability is rarely evidenced. Here, we empirically investigated the replicability of associations of an extended range of psychometric variables and CT in a large cohort of healthy adults. Our analyses revealed low likelihood of significant associations. Furthermore, significant associations from exploratory analyses showed overestimated effect sizes and were rarely replicable in an independent sample. We discuss the interpretation and implications of these findings within the context of accumulating evidence of the poor replicability of structural-brain-behaviour associations using grey matter volume, and more broadly of the replicability crisis of brain and behaviour sciences.