We can tell a lot about how a person is feeling by looking at their face and, for the most part, we’re good at it. We can assess a variety of emotions (such as fear, joy, anger) in a variety of contexts (across cultures for example).
A useful way to utilize this skill, is to tell whether a person is in pain or not. In a historic sense (before the development of spoken language), facial expression would serve a communicative function telling others in our group that we need help. Now, pain expressions are used as a part of grimace scales to aid doctors, particularly when dealing with pre-verbal children.
Grimace scales work by coding ‘action units' (or, facial features) that change when someone is experiencing pain. The severity of changes in these action units relates to the severity of the pain being experienced. It appears, that grimace scales are fairly universal across cultures and even different ages.
An interesting question then, is: Can grimace scales also be developed for animals? It would appear that the answer is yes! There’s evidence that mice, rats, rabbits and macaques have a ‘pain face’ and that the action units that comprise this face are similar to those of humans.
What I’ve recently been interested in, is seeing if sheep also show pain in their faces. We already know that sheep express pain in their behaviour and physiology and that sheep can recognize each other’s faces. That means there is potential for them to use facial expressions as a way to communicate to each other that they are in pain.
I’m trying to answer this question by taking still images from live video footage of lambs before and after docking. I then compare them to see what ‘action units’ are potentially there. From there, I’ve developed a Lamb Grimace Scale (similar to what’s been done with mice/rabbits etc.). I’m now seeing whether naive people can tell the difference between a lamb that’s in pain and a lamb that isn’t using the scale I’ve developed.
So, look at the pictures below. What do you think? Do lambs have a ‘pain face’?