Evolutionary echoes of emotion: Humans mimic other primate expressions.
Level 4 - case-series / case-control
Laboratory observational and experimental study testing human facial reactions to primate video stimuli.
PubMed 41811835 · doi:10.1371/journal.pone.0342196
What was done
Human observers watched short video clips featuring monkeys and apes displaying positive (play-face), negative (open-mouth threat display), or neutral facial expressions. Participants' facial expressions were filmed and analyzed via automatic coding software. Participants also rated the emotional content of the expressions and reported their subjective feelings of liking and closeness toward the primates.
What was found
The abstract reports no quantitative values, confidence intervals, or statistical test results. It qualitatively reports that human observers mimicked both positive and negative primate expressions and accurately categorized the emotional valence (positive or negative) of the displays.
Why it matters
This study suggests that automatic facial mimicry and emotional mirroring are not strictly species-specific, indicating shared evolutionary mechanisms for recognizing and reflecting emotional expressions across primate lineages.
Limits
The abstract does not disclose the sample size, demographic characteristics, or the specific species of monkeys and apes used. Detailed quantitative effect sizes, baseline facial movements, and potential modulation by individual animal affinity or prior animal experience were not reported in the abstract.