# Individual differences in learning and decision-making: the role of COMT Val158Met polymorphism in transitive inference

## TL;DR

This study shows that a genetic variation in the COMT gene affects how quickly people learn and adapt to changing hierarchies in decision-making tasks.

## Contribution

The study reveals that COMT Val158Met genotype influences learning efficiency and cognitive flexibility in transitive inference tasks.

## Key findings

- Val homozygotes learned more slowly than Met homozygotes and heterozygotes during the learning phase.
- Drift diffusion modeling showed Val homozygotes had lower evidence accumulation efficiency, affecting performance in reversed hierarchies.
- Genetic variation in COMT may partially explain individual differences in inferential decision-making and cognitive flexibility.

## Abstract

Understanding the ordinal relationships between items organized hierarchically requires constructing a rank order supporting decision-making between options. This process depends on the ability to learn reciprocal relationships and to select the best option available when making a choice. In such forms of decision-making, the prefrontal cortex (PFC) plays a crucial role in encoding the relative value of alternatives as a decision is formed. Higher-order cognitive abilities are influenced by genetic factors that affect dopamine availability in the PFC, potentially contributing to individual differences. Here, we examined the performance of 83 participants in a transitive inference (TI) task, grouped by genotype based on the Val158Met single-nucleotide polymorphism in the Catechol-O-Methyltransferase (COMT) gene. The task included a learning phase in which participants acquired the reciprocal relationships among a set of hierarchically ranked items (A > B> C > D> E > F), followed by a test phase in which they were required to compare all possible item pairs and select the higher-ranked one. While genotype did not significantly influence test-phase performance, it did affect learning efficiency. Specifically, Val homozygotes took a longer learning procedure than both heterozygotes and Met homozygotes during the learning phase. Drift diffusion modelling (DDM) revealed that task performance was explained by the efficiency of evidence accumulation, which was lower in Val homozygotes, accounting for their poorer performance not only during initial learning but also when required to switch to a reversed hierarchical structure (A < B< C < D< E < F). These findings suggest that individual differences in inferential decision-making and cognitive flexibility may be partially driven by genetically determined variations in prefrontal dopamine availability.

The online version contains supplementary material available at 10.1007/s00221-026-07247-4.