Is aggression related to inhibitory control in a free-living female songbird?

Aggression in nature is common and has garnered considerable attention as a personality trait. However, what regulates individual variation in aggression remains poorly understood, particularly in females. Recent research suggests that personality may covary with cognitive ability. In mammals, numerous studies have identified an association between aggression and inhibitory control. Inhibitory control is a core executive function, often considered a domain-general cognitive process that supports behavioral regulation across diverse contexts. However, few behavioral studies have assessed whether inhibitory control may regulate aggression in non-mammalian species and in wild animals, with females also tending to be underrepresented in prior research. We investigated the relationship between aggression and inhibitory control in free-living female blue tits (Cyanistes caeruleus). By examining aggression and inhibition in the ecologically relevant context of nesting, we aimed to enhance our understanding of female aggression. We performed simulated territorial intrusions to assess aggression and detour-reaching tasks to measure inhibitory control. Multivariate analysis showed no significant association between inhibitory control and aggression. Our results suggest that aggressive behavior may not be regulated by inhibitory control or by a common proximate mechanism in free-living blue tit females. However, blue tits performed overall very well on the detour-task, which may have limited our ability to detect an association with aggression. More studies examining the regulatory mechanisms of aggression are needed and may benefit from comparisons across taxa.