Muscle activity shows true face of horses
What goes on in a horse's head? A better understanding of horses' emotions allows us to improve their well-being. That is the idea behind the project of researchers Ineke Smit and Nikae te Moller, which was launched with financial support from the Veterinair Vuur (veterinary relay) campaign. They are measuring muscle activity in horses' faces in collaboration with the Swedish University of Agricultural Sciences, SLU.
A face full of electrodes and a bundle of cables along his body: Cade the horse has seen it all many times before. "He enjoys all the attention and contact", say Ineke Smit and Nikae te Moller from the Faculty of Veterinary Medicine (Utrecht University), as they carefully hook up the tech. Looking at Cade, we agree that the animal is quite happy with everything that is happening to it. It’s a great example of how easily we think we recognise emotions in horses, which is precisely the mission of the two researchers. "We want to identify facial expressions and associated emotions more objectively and in greater detail", says Te Moller.
Measuring facial muscles
Assessing the facial expressions of horses is nothing new. "Vets already look at the eyes, ears and nose, for example, to gauge whether a horse is in pain somewhere. It’s just difficult to determine the strength of the pain with the naked eye", explains Te Moller. Smit adds: "Plus the emphasis now is on identifying pain, whereas, from an animal welfare perspective, we are also interested in recognising positive emotions."
"It’s why we want to refine the current method and make it more objective", she continues. "We do this by measuring the activity of the muscles that cause the expressions." Electrodes in the horse's face measure how much the facial muscles are activated to tighten. The researchers studied equine anatomy in order to carefully determine the position of the electrodes. This allows them to limit discrepancies in measurement results between different horses. To this end, they studied horse heads in the dissection room together with colleagues from the Anatomy Department of Veterinary Medicine. As well as muscle activity, they use infrared cameras and dots on the horse's face to measure how much movement the muscles actually cause.
From measurement to emotion
The measurements thus accurately portray the horse's expressions. But how do you then translate this into emotions? Smit: "We use positive and negative stimuli during the measurements. For example, in the case of positive stimuli, such as offering a carrot or playing horse noises, the horse will lift its head and prick up its ears. In the case of negative stimuli, a loud noise or a tickle in the groin for example, the corners of the mouth and inside of the upper eyelids are raised. That way, we link the expressions measured to positive or negative emotions. We can then interpret these in future measurements."
"Together with other factors, such as heart rate and breathing, a picture of the horse's mood quickly emerges", explains Smit. "For example, we can objectively measure the effects of pain medication after surgery. Or discover what makes a horse happy so we can look after it better. These are tools for vets, owners and researchers. Although that’s still a long way off."
Insight into a horse's head
Initially, Smit and Te Moller expect to use the new method primarily as a tool for research. Te Moller: "Our project is still in the fundamental phase. What the next step will be depends on the data that we’re currently analysing." Smit: "There is a clear need among the scientific community for objective tools to measure different types and strengths of pain."
No electrodes are needed to gauge the emotions of the researchers themselves: They are clearly enthusiastic about the subject. Te Moller: "We’re working on something new and are exploring a fundamental question: What does a horse feel? It's great to be able to get a bit closer to understanding that." Smit: "I find it interesting to be able to put a number to what a horse is experiencing. We get an insight into a horse’s head and, ultimately, we hope that this will make a difference in terms of equine welfare."
Children's thesis on lameness in horses
Ineke Smit was awarded a PhD in spring 2024 for her research on the measurement of movement in horses. She believes, however, that science is not just for scientists. That is why she wrote a children's thesis that teaches children how to recognise pain in horses and introduces them to research. "I hope to get at least one child excited about becoming a veterinarian or researcher."