In the study, the horses were kept in family groups and began their "training" from birth. Each week, for 15 minutes, they attended a covered "schoolroom," where they were paired with human volunteers who helped them to learn.

They were taught the words for objects such as buckets and blankets. To learn the words for actions, they were shown a gesture while the word was spoken. The gesture was later dropped so that the horse had to respond to the word alone.

The animals, which have also been tralned to imitate Dr. Kiley-Worthington's gestures~ were sometimes taken out on "structured expeditions." Here, people spoke clearly about what the horse, or the human, is doing; For example "Shemal (the horse) eats the grass." Or: "Jane (the human) picks the buttercup."

Dr. Kiley-Worthington claims that her students can now select blue, red or yellow buckets, after being given only verbal cues, and will perform actions, such as kicking a ball or picking up a blanket, on command.

She said the animals appeared to react to words such as "scared' in the
way they would normally react to a human who was exhibiting obvious physical signs of the emotion.

"One of my horses will yawn if you ask him to. Another will stop putting his nose to the ground if you say 'prickly,' despite the fact that there is no evidence that the greenery he is about to eat is sharp or spiky," she said.

"They react to the word. We use no gestures. By teaching your horse to listen to words and understand their meaning, he can learn to do many things on word command alone. The research has some way to go, but the early signs are very encouraging."

The study had begun, she said, as an extension of her 25-year research into equine welfare and behaviour, the subject of her books.  Her latest work, Equine Welfare, has a chapter on cognition.

She said: "Clearly, because of their different musculature and cognitive system, horses are not going to learn to speak. But our training and research show that they have far greater powers of comprehension than previously suspected. The animals we are working with now appear to understand at least 300 words."

Dr. Kiley-worthington said the training echoed the developmental   psychology techniques used to study the comprehension of children who had not begun to talk. "Years ago, everyone was conditioned to believe  that animals acted only on instinct,  that they had no cognitive thought," .  she said "Nor did anyone believe that   they could relate to human cognitive  thought."

But are the animals merely learning tricks? How much can they realiy understand? It has always been presumed that what separated humans   from animals was self-awareness and the  use of language.

But research in other animals, particularly primates, has shown that this  might not be the case. The world was  astonished when Roger Fouts, an animal behaviourist, taught a chimpanzee  called Washoe to talk, using sign language.