Blushing was once considered the “most peculiar and most human of all expressions”, as Charles Darwin stated, but a new study has found that chickens share this quirk and can 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,” Aline Bertin, study co-leader and researcher at France’s National Institute for Agricultural Research, told CNN.
Together with researchers from several French institutes and the University of Tours, also in France, Bertin’s study found that chickens ruffled their head feathers when they were happy and calm, and that blushing for a few seconds indicated a reaction to excitement – in positive situations, such as 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 blush in a matter of seconds during strong emotions.”
A slightly red expression and ruffled head feathers suggest that chickens are calm and secure, providing knowledge that can be used to assess their well-being, concluded the study, published Wednesday in Plos One magazine.
While facial expressions have been investigated in several other mammals, such as dogs, horses, pigs and mice, it has not been as widely studied in birds.
To understand how chickens visibly express their 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 very easily startled by the slightest noise, while others reacted much less,” Bertin said, adding that these individual differences are an area for future study.
To make their conclusions more general, 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 – mainly 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 influence skin color change.
However, to mitigate this, the researchers analyzed the images using infrared thermography, which did not produce the same effect, suggesting there was little change in temperature and the colors in the images were relatively well balanced.
Of course, there is a subjectivity when analyzing human emotions, let alone the emotions of animals.
“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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