Scientifically measuring the changes in a cat’s facial expression when in pain

This is an interesting but bafflingly complicated study about measuring facial expressions in non-human animals. I’ll summarise it in my own way but if you are interested you should read the full report on (see link at base of page). It should be of interest to concerned cat guardians as it helps to read a cat’s feelings. This is potentially very valuable in communicating with our cat companions.

In the study the researchers used cats suffering post operation pain to measure the changes in their facial expressions when in pain. It might have been a different animal and a different reason for a change in facial expression but they chose female cats and pain after the spaying operation (ovariohysterectomy).

Facial landmarks on cat showing facial expression when in pain
Facial landmarks on cat showing facial expression when in pain. The landmarks move as indicated by the arrows. Photo: See base of page.
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They used a technique called geometric morphometrics for the first time in trying to measure the facial expressions of animals (as I understand it). This technique entails placing markers (facial landmarks) at various points on the cat’s face and seeing how those markers move when in the animal suffers pain. In this way it is possible to objectively measure how the face changes in shape when expressing an emotion. It is very difficult to spot clear facial expressions in cats and other animals so geometric morphometrics is a useful advance in that area.

I think they use the same method in CGI for movies when an actor is transformed into a different creature like Gollum played by Andy Serkis acting in front of a green screen.

This study on cats suffering pain will be useful for “the automatic, objective detection of emotional expressions in a range of non-human animal species”.

The image in this page (above) shows a ginger tabby-and-white cat with 48 facial landmarks (the yellow dots) and the direction of travel of those precise areas of the cat’s face during increased pain intensity.

The way I read this – and I am drastically simplifying – the cat’s ears move downwards and away from the middle of the head at the tip of the ear flap. The eyes close slightly. The muzzle seems to become ‘pinched’ as the arrows move inwards. The arrows all point towards the point where the base of the nose leather meets the mouth.

My former female cat in pain I believed.
My former female cat in pain I believe. Photo: Michael.

I can relate to this pained face as I have seen it in my late female cat who had chronic kidney failure. It is a reminder that kidney failure causes pain (see image on this page).

How can this benefit cat owners? The first point is that it can be difficult to tell if your cat is in pain. If your cat’s face shows slightly closed eyes, a ‘pinched’ muzzle and slightly less erect ears she/he might be showing signs of pain.

P.S. An interesting aspect of this is that the researchers must be sure that the cat feels the post-op pain. I suppose that information came from veterinarians. Also it is common sense. Another aspect of this is that I presume that the cats were denied post-op pain killers.

Source: Geometric morphometrics for the study of facial expressions in non-human animals, using the domestic cat as an exemplar by Lauren R. Finka, Stelio P. Luna, Juliana T. Brondani, Yorgos Tzimiropoulos, John McDonagh, Mark J. Farnworth, Marcello Ruta & Daniel S. Mills.

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