Bruchmann, C. | bioRxiv Science

bioRxiv2025

Spontaneous eye blinking is influenced by activity, synchronized with attentional breakpoints, but not modulated by social relevance in Barbary macaques

Spontaneous eye blinking is a ubiquitous behavior in animals including humans necessary for lubricating the ocular surface and preventing dryness. Beyond this functional role, eye blinking also provides a window into an animals cognitive state and attention allocation. Here, we investigated in 13 female Barbary macaques the modulation of spontaneous eye blinking during two naturally occurring activities differing in their attentional demand (resting and allo-grooming) and additionally assess the influence of social relevance of the interaction on attention allocation. Eye blink rates were significantly lower during grooming compared to resting, suggesting increased attention during this cognitively more demanding task. Dominance rank difference and affiliative relationship strength between the groomer and groomee did not additionally influence eye blink rate. Blinking was timed to coincide with ingestion events during grooming, which may serve as explicit attentional breakpoints. By systematically timing blinks with periods of decreased visual demand, macaques effectively minimized information loss during the non-visual phase of the grooming process. Our study provides insights into the regulation of spontaneous eye blinking in nonhuman animals using a non-invasive tool for the study of visual attention and cognitive load.

animal behavior and cognition↗

bioRxiv2020

Grooming interventions in female rhesus macaques as social niche construction

Social animals invest time and resources into building and adapting their social environment, which emerges not only from their own but also from the decisions of other group members. Thus, individuals have to monitor interactions between others and potentially decide when and how to interfere to prevent damage to their own investment. These interventions can be subtle, as in the case of affiliative interactions such as grooming, but they can inform us about how animals structure their world and influence other group members. Here, we used interventions into grooming bouts in 29 female rhesus macaques (Macaca mulatta) to determine who intervened into which grooming bouts, why, and what determined intervention outcomes, based on kinship, dominance rank, and affiliative relationships between groomers and (potential) interveners. Using 1132 grooming bouts and 521 interventions, we show that high dominance rank of groomers reduced the risk of intervention. Bystanders, particularly when high-ranking, intervened in grooming of their kin, close affiliates, and close-ranked competitors. Interveners gained access to their close affiliates for subsequent grooming. Affiliative relationship and rank determined intervention outcomes, with reduced aggression risk facilitating grooming involving three individuals. Thus, interventions in this species involved the monitoring of grooming interactions, decision-making based on several individual and dyadic characteristics, and potentially allowed individuals to broaden their access to grooming partners, protect their own relationships, and influence their social niche.

animal behavior and cognition↗