Eye wrinkle expression characteristics in horses may be linked with emotional states and could be an indicator of horse welfare, researchers have said, although more research is needed.
They are often referred to as worry wrinkles or worry lines but to date, no scientific study has investigated the effect of emotion on the expression of eye wrinkles.
Researchers from Switzerland, the UK and US asked whether eye wrinkles are caused by negative emotional states in the horse, or whether they are simply an anthropomorphic interpretation based on the fact humans associate wrinkles at the inner eye brow with worry.
The aim of the study was to investigate whether there was a relationship between eye wrinkles and emotional states in horses. The study took place at the Swiss National Stud Farm in Avenches, Switzerland.
Researchers induced different emotional states in the horses and assessed whether situations presumed to be positive, such as the anticipation of a food reward, would reduce the expression of eye wrinkles, or if situations presumed to be negative, such as competition for food, would increase it.
Analysis of the number of wrinkles, the extent of wrinkling and how much white of the eye was shown led to the conclusion some characteristics of eye wrinkling were affected by different emotional states.
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