Blushing was once considered the “most peculiar and most human of all expressions”, as Charles Darwin put, but a new study found that chickens share this peculiarity and may also express their fear or excitement in this way.
“Our research shows that domestic chickens are sensitive and have very subtle ways of expressing their emotions,” study co-leader Aline Bertin, a researcher at the National Institute of Agricultural Research, told CNN.
Together with researchers from several French institutes and the University of Tours, Bertin’s study found that chickens shook their head feathers when they were happy and calm, and that blushing for a few seconds indicated a reaction to excitement – in positive situations like waiting to eat mealworms –. as well as fearful situations, such as being captured.
“In humans, blushing is often associated with shame or embarrassment, but it also appears in the expression of a range of emotions, such as anger or joy,” Bertin added. “Although a chicken’s emotions are not directly comparable to those experienced by humans, we have shown that they also turn red within seconds during strong emotions.”
A low-red expression and fluffy head feathers suggest the chickens are calm and secure, providing knowledge that can be used to assess their well-being, says the study, published Wednesday in Plos One magazineconcluded.
Although facial expressions have been investigated in several other mammals, such as dogs, horses, pigs and rats, they have not been studied as extensively in birds.
To understand how chickens visibly express emotions, researchers spent four weeks on a French farm observing 17 chickens of two different breeds, Bertin said, filming their routine behaviors and their reactions to different stimuli.
Each had their own quirks and personalities – some “were easily startled by the slightest noise, while others reacted much less,” Bertin said, adding that these individual differences are an area for further study.
To draw more general conclusions, the researchers extracted images from every two seconds of film and selected those that featured the chicken in profile to better study them.
Although the researchers were unable to explain the mechanism by which chickens blush in this study, they concluded that the cheeks and earlobes were more revealing of the birds’ emotions than the crest or wattles.
The researchers acknowledged the limitations of their conclusion – namely that filming chickens in their natural habitat without a controlled light source could make it difficult to identify specific color changes, while temperature changes could also have influenced the change in skin color.
However, to mitigate this situation, the researchers analyzed the images using infrared thermography which did not produce the same effect, suggesting that there was little change in temperature and that the colors in the images were relatively well balanced.
It is clear that there is subjectivity in the analysis of human emotions, much less animal ones.
“Without language, subjective experience remains inaccessible,” Bertin said. Instead, scientists define emotions as “behavioral, physiological and cognitive responses to environmental stimuli,” she said, and measure things like heart rate or observe an animal’s behavior.
Based on the results of this study, Bertin hopes to investigate whether these displays of emotion are linked to the chickens’ social interactions, as well as the implications for animal welfare.
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