The facial expression for disgust is universal. We can all picture the contorted, horrified face which communicates a feeling of revulsion and loathing. Spiders, slimy creatures, mucus and faeces can all provoke this feeling. Our reaction is to distance ourselves from the cause. As a result, feelings of disgust help us to avoid, or at the very least recognise, the things that make us feel this way - and for a very good reason, psychologists say.