Question: it is easy to notice if a dog is happy,sad or angry/defensive due to behaviour. If it is happy then it will wagg it's tail,if it is sad it will whine, if it's angry it will bark and on some occasions bite you. But what exactly are you trying to do?

Anne Seawright answered on 15 Mar 2010:

Very good question and the answer is that it actually isn’t easy at all to tell what emotions a dog is feeling. You can often tell a lot by looking at body language and how the animal behaves in different situations (these are called behavioural measures) but they can be confusing. For example a dog wagging its tail is often thought of to be happy as you suggested, but dogs wag their tails when they are aroused for any reason, so a dog could wag its tail if it is fearful. Dogs can also whine or bark through excitement or anticipation of something like food or a game and so this again could be positive or negative. So what the behavioural measures often tell us is whether a dog is calm and unaroused, or aroused, but not whether that arousal is positive (ie happy) or negative (ie sad, angry, fearful etc).
We can also look at measures of certain changes in the body, such as heart rate, breathing rate, stress hormones etc to try to tell what emotions a dog is feeling (these are called physiological measures). So for example, if a dog is stressed about something, such as another dog that it is scared of, its heart rate and respiratory rate will increase to allow the dog to have the energy to do something about it, such as run away (this is the fight or flight response). However, like the behavioural measures, the physiological measures can also change for other things, such as excitement, exercise etc and so they again don’t tell us the full picture.
So this is where my research comes in! I am looking at new measures to try to tell us more accurately what emotion a dog is feeling by measuring whether it sees the world optimistically (and thereofre is feeling positive emotions) or pessimistically (and feeling negative emotions). I do this by offering the dog a positive marker on the left with food in it, or a negative marker on the right with no food and then offering it a marker in the middle with no food. We then time how long it takes the dog to go to the middle marker. If the dog is optimistic it will go to the middle marker fast as it will hope there is will food in it, whereas if it is pessimistic it will go to it more slowly (or not at all in some cases!) as it will assume it will be empty. This has been seen in people, in rats and in birds and so I am going to see if it works in dogs as well. It will obviously then be very useful to use this to measure how dogs are feeling in general and how they respond to time in kennels for example, or time in vets.

I hope that made sense!

Anne