Animal emotion part 2b: Pounding hearts and shaky bodies
This series has looked at what emotions are, whether animals have the capacity to experience them, and come up with a generalized framework for studying emotion in animals. How then can we use this framework to measure emotion? The answer to this is, it depends what you want to find out.
One way is through physiological measures. In other words, measuring bodily processes in various states. A change in a process under certain conditions would then relate to an emotion. You can measure things like heart rate, skin temperature, eye aperture or cortisol levels. For example, the emotion of fear has been associated with an increased heart rate and lower skin temperature. People like this approach because it’s easy to quantify things but it becomes a little bit tricky to discriminate between emotions with similar physiological responses. Another thought: How do we measure positive emotions? Feelings like joy often don’t have huge marked changes in physiology as, say, anger or fear...
A subset of physiological measures that often receives a lot of attention is measuring brain activity. Areas of the brain that are activated in certain conditions relate to a particular emotion. Brain activity measures include: EEG, fMRI and MRI. I’m not going to go into detail about how each of these methods works, but the basic idea behind them all is an animal is hooked up to some kind of machine that then scans the brain’s activity when it’s viewing/doing something to elicit a particular emotion. An example here is that feelings of disgust in apes is associated with the amygdala, thalamus and prefrontal cortex being activated. The reason this methodology is so popular is because, intuitively, it’s not very far removed from the place emotion is generated. What I mean by this, is that people often perceive emotions originating from the brain. By measuring the brain therefore, it’s thought we are actually measuring the emotion itself (although as I’ve said earlier, this is clearly not the case). The problem however, is that undertaking these procedures can be quite invasive. Also, not all brains are created equal. Chicken brains are different structurally from cat brains are different from human brains. This means that it becomes difficult to compare across species.
Another approach, is to look at what the animal is doing (it’s behaviour). The assumption behind this method, is that an animal behaves a certain way to fulfil biological needs and these needs are driven by emotion. A simplified example of this idea is we see an animal displaying foraging behaviour, we assume it’s fulfilling it’s biological need to eat, driven by a feeling of hunger. Behaviour can be quantifiable (by using ethograms and getting the rate or proportion of time an animal is doing a certain activity) but can be difficult to analyse statistically. If you get a data set that’s normally distributed, you’re one of the lucky ones!
Physiology and behaviour are two sound ways that we can gain insight into what animals are feeling. They’re both great because they have been used a great deal, meaning scientists can base their own research on methodologies that have already been established by others. This also allows us to readily compare the results of our studies with previous ones. They aren’t the only two measures, however.
Next time, I’ll be discussing some of the more recent ways scientists have tried (and are still trying!) to study animal emotion. Stay tuned!