Biology subjects

Taubert, N.

Publications and source records attributed to Taubert, N..

4 recordsLinked to original sources

bioRxiv2026

Behavioral evidence challenges species-specific ocular morphology as a primary constraint on human gaze-following

Previous research suggests that humans are extremely sensitive to object-directed eye gaze, which effectively guides their attention toward objects of shared interest. This contrasts with non-human primates, who typically require much more salient eye-gaze cues to achieve comparable attentional orienting. However, it remains unclear whether cross-species differences in ocular morphology account for this performance gap. To address this question, we examined humans covert shifts of spatial attention in response to eye-gaze cues provided by either realistic human or rhesus monkey head avatars. Target detection was reliably enhanced on gaze-congruent compared to gaze-incongruent trials, with comparable gaze-cueing effects for both avatar types, despite the fact that monkey eyes lack many of the conspicuous features characteristic of human eyes. Hence, eye morphology alone does not substantially modulate gaze-driven attentional orienting in humans, whereas humans reliable use of monkey eye-gaze cues highlights a clear species difference in perceptual sensitivity to eye gaze signals. Significance StatementEye-gaze-mediated attentional orienting is a conserved ability across primates, yet sensitivity to subtle eye-gaze cues may differ between species. Here, we provide empirical evidence that humans exhibit a quantitatively greater capacity than non-human primates to follow subtle eye-gaze cues. Importantly, we showed that this difference cannot be attributed to species-specific ocular morphology as human participants showed robust and comparable reflexive attentional orienting to both human and rhesus monkey eye-gaze cues. This is striking given the pronounced differences in ocular morphology and coloration/contrast between the two species. These findings suggest that cross-species diversity in extracting spatial information from eye-gaze cues likely reflects differences in perceptual sensitivity rather than bottom-up constraints imposed by species-specific ocular morphology.

neuroscience↗

bioRxiv2026

Behavioral characterization of dynamic facial expression perception in rhesus monkeys (Macaca mulatta) using naturalistic and synthetic stimuli

Facial displays are an important channel of communication for primates, yet it remains unclear based on which criteria monkeys evaluate facial expressions. We trained two rhesus macaques to categorize videos of four facial expression types (neutral, lip-smacking, silent bared-teeth (SBT) and open-mouth threat displays) and then tested generalization to novel individuals and avatars while measuring pupillary responses. The animals were able to categorize facial expressions and generalize their classifications to novel, untrained videos, although performance was not perfect. Misclassifications were not driven solely by visual similarity between expression categories, as demonstrated by a novel automated approach integrating deep learning-based motion tracking with the Macaque Facial Action Coding System to enable objective quantification of facial action units. Instead, open-mouth threats were readily categorized correctly and distinguished from lip-smacking, while also eliciting the strongest arousal responses. By contrast, categorization of SBT displays varied substantially across stimulus identities, influenced by body weight, gaze direction, and coordinated movements of eyebrows and ears. Morphed avatar expressions were categorized according to expression component intensity, demonstrating graded perception. Avatar manipulations revealed that categorization was robust against lack of coherent motion, lack of realism beyond a basic level of texture, and to some extent transcended species form boundaries to a human face. However, human facial expressions elicited no systematic categorizations or differential arousal. Our findings indicate that conspecific facial expressions were perceived as functionally meaningful, context-dependent social signals shaped by all components of facial behavior and signaler characteristics, rather than fixed, mouth movement-defined categories.

animal behavior and cognition↗

bioRxiv2025

Rhesus monkeys use both eye and head gaze to reallocate covert spatial attention facilitating visual perception

Non-verbal cues, particularly eye gaze, significantly shape human social interactions. Although non-human primates reliably follow head gaze, their capacity to use eye gaze alone for inferring the others focus of attention remains debated. We investigated this question using a realistic rhesus monkey head avatar that directed its gaze toward one of two LEDs (left or right), employing either eye movements alone or combined eye and head movements. After a randomly chosen interval (ranging 50-400 ms) from gaze presentation, one LED transiently increased its luminance to near-threshold levels. Rhesus monkeys were trained to detect and report this luminance change via a saccade to the corresponding LED, independent of the avatars gaze direction, to receive rewards. Our results showed that head-gaze cues robustly directed covert attention toward gaze-congruent targets with short delays, indicative of reflex-like, stimulus-driven orienting. In contrast, eye gaze alone, at comparable amplitudes, did not affect attention shifts. However, increasing the avatars size and eye-gaze amplitude, simulating a close-range interaction, made eye gaze cues effective in guiding attention. These findings demonstrate that rhesus monkeys possess the capacity to use eye-gaze cues to determine conspecifics attentional targets, and validate and underscore the utility of 3D animal models as powerful tools for generating realistic yet precisely controlled stimuli. Our study supports the idea that eye-gaze following is not uniquely human but is an evolutionarily ancient ability, likely shared across Old World monkeys and apes which diverged more than 30 million years ago.

animal behavior and cognition↗

bioRxiv2022

A large-scale brain network of species-specific dynamic human body perception

This ultrahigh field 7T fMRI study addressed the question of whether there exists a core network of brain areas at the service of different aspects of body perception. Participants viewed naturalistic videos of monkey and human faces, bodies, and objects along with mosaic-scrambled videos for control of low-level features. ICA-based network analysis was conducted to find body and species modulations at both the voxel and the network levels. Among the body areas, the highest species selectivity was found in the middle frontal gyrus and amygdala. Two large-scale networks were highly selective to bodies, dominated by the lateral occipital cortex and right superior temporal sulcus (STS) respectively. The right STS network showed high species selectivity, and its significant human body-induced node connectivity was focused around the extrastriate body area (EBA), STS, temporoparietal junction (TPJ), premotor cortex, and inferior frontal gyrus (IFG). The human body-specific network discovered here may serve as a brain-wide internal model of the human body serving as an entry point for a variety of processes relying on body descriptions as part of their more specific categorization, action, or expression recognition functions.

neuroscience↗