Of Mice and Monkeys: Facial expressions reveal internal cognitive states in mice and monkeys

Much like in humans, facial expressions in mice and monkeys reflect internal factors that directly relate to subsequent behavior. A new research study published in Nature Communications, suggests that the relationship between facial expressions and internal cognitive states extends beyond the human species. Overall, the study showed that pretrial facial expressions could indeed predict subsequent performance in the assigned task.

NICOLAS DAVIDENKO: Long-standing research in human psychology has claimed that certain facial expressions of emotion are universal across cultures. For example, classic cross-cultural studies by Paul Ekman and colleagues argue that certain “basic emotions” (happiness, sadness, anger, fear, surprise, and disgust) are not only shared across human cultures, but they are also signaled by very similar facial expressions. Moreover, facial expressions can also signal internal cognitive states (such as attention or inattention), which can be used to infer subsequent behavior.

In a new research study published in Nature Communications, Alejandro Tlaie and colleagues suggest that the relationship between facial expressions and internal cognitive states extends beyond the human species. In their study, the researchers trained two monkeys (Macaca mulatta) and six mice (Mus musculus) to navigate a naturalistic virtual foraging environment using trackballs. The animals were trained to search for certain targets while avoiding others, receiving drops of diluted juice (for the monkeys) and drops of vanilla soy milk (for the mice) when they reached a desired target. A camera tracked the animals’ facial expressions as they navigated the virtual environment…

Overall, the study showed that pretrial facial expressions could indeed predict subsequent performance in the foraging task. In mice, pupil size and whisker movements predicted reaction times during target trials, but nose movements were better at predicting reaction times in non-target trials… The findings highlight the importance of considering the complex changes in animals’ faces rather than focusing on isolated features such as pupil size. In addition, the link between facial expression and behavior is not fixed but rather depends on the internal state of the animal. Therefore, much like in humans, facial expressions in mice and monkeys reflect internal factors that directly relate to subsequent behavior. SOURCE…

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