There seems to be significant confusion about what happened in the British parliament when MPs discussed a proposed amendment to the EU (Withdrawal) Bill to formally recognise animal sentience. But where science is concerned, animal sentience is in no doubt.

The definition of sentient is simply “able to perceive or feel things”. Today most of us would probably also say that animals are able to feel emotion, form attachments and have distinct personalities. Yet for many decades the idea of animals feeling emotions or having personalities was dismissed by behavioural scientists. This strange view that arose from the 17th century philosopher René Descartes’ alleged assertion that animals are without feelings, physical or emotional.

Recent work has debunked this idea (whether or not Descartes actually said it). If any mammal appears to be free of emotions, apart perhaps from cynicism, it would be the goat. Yet scientists have been able to show that goats become emotionally aroused in response to various test situations, and whether these emotions are positive or negative.

The researchers analysed the calls the goats made when they were expecting food, when they were frustrated because a food reward didn’t arrive and when they were isolated from their herd mates. They also used the goats’ body language and heart rate to calibrate their assessment of the emotions expressed in the calls, as analysed using the frequency of the sounds.

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Horses are a bundle of emotions. This is not surprising, given that they are very social animals, with a close relationship with others in their herds and are also prey animals whose response to threat is to run away as fast as possible. In Canada, horse riding is reckoned to be one of the most dangerous sports, ahead of motor racing and skiing, and the emotional state of the horse is an important aspect of the safety or otherwise of the rider.

Researchers in France looked at the level of emotion and the ability to learn shown by 184 horses from 22 different riding schools. The ability of a horse to be fairly calm in the face of a novel situation, and to learn quickly that a new object or situation is not threatening, is crucial when riding. So the researchers concentrated on these aspects of horse emotion.

They found that one of the most important influences on how emotional horses are is the way that they are housed. Horses that were kept outside in a field were likely to be less fearful of a new object and to respond with less excitement to being loose in an arena than horses that were housed individually in boxes. While the result is not surprising, the study emphasises the fact that horses are capable of emotions such as anxiety and fear.

Another vexed question, in the early part of the 20th century at least, was whether or not animals have personalities. It is now generally accepted that they do, and that those personalities are capable of as much variation as human personalities.

Perhaps the most surprising aspect of this area of study is that personality is discernible even in fish, which are often seen as being singularly lacking in emotional range. Scientists have found that the personality type of a fish may affect its likelihood of having certain parasites, or its ability to move past a barrier in a stream when on migration.

Why it matters

The reason that all these studies and the many others into animal emotions, personality and ability to feel pain, fear and stress, are important is the huge implications for animal welfare. Whether or not the law recognises animals as being sentient, those animals will still feel afraid, fail to cope or suffer pain during transport and slaughter, as well as in everyday situations.

It is difficult to reduce the fear and stress endured by animals going to slaughter, or being used in sport, entertainment or as companions. But it is likely to be even more difficult if the law does not recognise animals as sentient beings, to whose welfare we should pay full regard.

Slaughter house personnel are perceived as being somewhat rough in handling the animals under their care, in spite of repeated training. Unless animal sentience continues to be recognised in law, it will be even more difficult to deal with people who compromise animal welfare.