'What we really want to do is work out what the emotional life of horses really is.
What their emotional world is really like.'
To build her library of horse emotions, Karen has designed a set of experiments to trigger them.
She plays recorded horse-talk and observes the response.
Startled and afraid, or curious.
She shows them photographs of horses and of humans.
Toffee likes this one.
This one isn't so popular.
Karen's team has made the surprising discovery that horses have 17 different facial expressions.
That's three more than chimpanzees and one more than dogs.
They're subtle, but by playing the images back, Karen can show me what the untrained eye might miss.
'He's sniffing the ground ostensibly, and you think, oh he's just sniffing the ground; another horse was in here but - stop.
Actually, that sniffing the ground again occurs consistently in response to something that's a bit more negative.
So that he's unsure about this.
Humans do that as well, you know when we're a bit uncomfortable, you might scratch yourself or we glance away from something, just gives us a little bit of time to adjust.
Now this will be interesting.
Look at what part of the face he's going to go to.
Look he's going towards the -' 'Right to the mouth.'
'Mouth, yeah and sometimes they go right up to the eyes, yep.
It's interesting, that sweep between the mouth and the eyes.
It's almost as if they understand that the mouth and the eyes are the most significant bit of the human face.
They have enough understanding to interpret not only emotion in the face of their own species but emotion in our faces.'
It makes sense that horses use emotions to communicate with each other, but what fascinates me is they can read our emotions as well.
'They're capable of putting together the sort of representation of the person with the emotion.
To me, that shows a very acute emotional awareness.'