The answer involves two baby chickens and a mirror.

Kenneth Sufka, professor of psychology and pharmacology, partnered with a team of animal welfare researchers in the United Kingdom to study avian emotions through the common domestic chick’s peeps and whistles. Their research was recently published in Applied Behaviour Science.

Their findings could improve animal welfare across the poultry production industry. It could also improve testing for medications to treat depression and anxiety in people.

“Is there a noninvasive way that can capture in freely moving animals a measure of stress states?” he said. “That was the question we wanted to address in this chick study, looking at the calling or the vocalizations that are emitted, but in a way more sophisticated way than I have ever done.”

To conduct the study, the UK researchers expanded on previous results from Dr. Sufka’s lab. The experimental set up involved complex acoustic equipment in a secluded room. In one box, they placed a chick, and in another, they placed a chick with a mirror.

The chicken that can see its reflection believes it is not alone, and its calls represent a relatively calm chick, that isn’t too stressed. The chick that is alone, however, begins to voice loud, higher pitched sounds that the researchers believe could indicate an anxiety-like state. The acoustic data the researchers gathered measured how the quality of the chick’s vocalizations changed, and what that meant for their stress level.

Being able to detect stress could open the doorway to more humane, responsive practices in the meat and egg industry.

“In production facilities, in commercial growing facilities across the board — be it cattle, swine or avian models like chickens — there’s a real concern about welfare,” he said. “Is this a worthwhile thing, to be thinking about using acoustics to monitor animal welfare in these production facilities? I think so.”

While researchers — and farmers — have long known that a loud chick is a distressed chick, the knowledge never went much deeper than that, said Sarah Collins, coauthor and associate professor of animal behavior at the University of Plymouth.

“This is more evidence of animal sentience — the ability to experience feelings,” she said. “We have known for a while that chick distress calls mean they are stressed, but knowing we can tell how stressed means we can assess welfare more precisely.”

The study also presents a noninvasive, comparatively inexpensive way to study anxiety-like states in animals. In previous models, the way to measure an animal’s stress levels included capturing it, withdrawing blood and measuring levels of corticosterone, a stress hormone.

“That itself is stressful — to capture, restrain, collect, release,” Sufka said. “This, we think, is a better way.”

Medications intended for humans often must go through chick, rat and primate studies before any testing on human subjects. But since chicks are often used as an early precursor to human studies, understanding their emotions could improve studies on anxiety and depression medication.

Like many humans, chicks are often resistant to many common depression medications, making them a prime subject for alternative treatments. But if researchers cannot prove that the chick first has anxiety-like symptoms, they cannot show that a medication improves that state.

“To claim that an anti-anxiety drug is alleviating an anxiety-like state, this chick or mouse or rat has to have an anxiety state similar to yours,” Sufka said. “The behavior (of an animal in an anxiety-like state) is totally different, but it’s behavior in the context of what that animal does.

“If I make an argument that I’ve got a drug that reduces that state, that would necessitate in a validation argument that animals have to have emotional states.”

But the research also points toward an answer to an older, more complex question: What rights do animals have? The long-held answer is that animals do not have the same emotional capabilities as humans, and therefore have fewer needs and wants.

“My argument is that all of the work that we have done to-date shows the similarities between this avian model and human anxiety and depressive states makes a very strong argument that these animals do have negative emotional states,” Sufka said.

“And if that’s true, then ethically it follows that we are absolutely obligated to be worried about animal welfare and provide for the best living conditions possible.”