Sustained attention and inhibitory control are fundamental cognitive functions that support perception, decision-making, and social behaviors. In humans, both capacities follow nonlinear lifespan trajectories, improving through childhood, peaking in adulthood, and declining with age. Dysfunction at any stage can impair daily functioning. Yet research is constrained by human longevity, is often cross-sectional, and is confounded by factors such as education and social status.
We investigated sustained attention and inhibitory control in 44 semi-free-ranging macaques (M. mulatta and M. tonkeana) living in rich social groups with unrestricted access to touchscreens for automated testing. This setup enabled animals to voluntarily engage with cognitive challenges in a naturalistic environment, bridging the gap between controlled experimentation and real-world behavior. We assessed sustained attention and inhibitory control using the 5-Choice Serial Reaction Time Task. We employed control tasks for working memory and visual acuity, quantified social hierarchy via semi-automated elo-ratings, and combined behavioral data with resting-state fMRI to characterize connectivity within frontoparietal attention and corticostriatal inhibitory networks. We hypothesized that, as in humans, sustained attention and inhibitory control in macaques would follow nonlinear lifespan trajectories at both behavioral and neural levels, with functional connectivity strength predicting individual differences in performance.
We found that sustained attention follows a nonlinear trajectory, peaking at 8 years. At the population level, inhibitory control declined linearly with age, yet individual differences in impulsivity remained stable across different cognitive tasks and over time, indicating trait-like characteristics. Working memory peaked earlier (5.9 years), and visual acuity declined linearly, indicating domain-specific trajectories. Social status significantly influenced performance, with higher-ranking individuals exhibiting greater accuracy and fewer errors, effects that diminished with age. In constrast, higher social status consistently predicted lower impulsivity across all ages. Distinct behavioral phenotypes emerged, including a subset of monkeys with persistent attentional deficits resembling ADHD-like profiles. Functionally, frontoparietal attention connectivity (LIP-FEF) showed the same inverted-U lifespan trajectory as behavior and robustly predicted attentional performance. In contrast, connectivity within corticostriatal inhibitory networks (NAcc-OFC, thalamus-NAcc) remained stable across the lifespan and predicted individual differences in inhibitory control.
Together, these findings reveal fundamental principles of how sustained attention and inhibitory control develop, decline, and vary across individuals and social contexts, establishing the macaque as a translational model for characterizing the neural and behavioral bases of cognitive control throughout the lifespan.
