Stage fright or "performance anxiety" is a more or less debilitating fear of public appearance. It ranges from mild distress to total panic and frequently impedes career development in the performing arts and professions that require public speaking. Like other phobias it is not amenable to reason. Exhorting a sufferer to "pull themselves together", like a pair of curtains, is unlikely to help.
Among the many techniques recommended for disarming the audience is to imagine them all sitting there nude; but nervous performers are more likely to feel as though they are themselves exposed in all their glory. In public speaking classes, it is often advised to ask yourself if there is anyone in the audience who knows more about the topic on which you are speaking than you? Unfortunately, if the answer is yes, you might be worse off than you started.
Stage fright is felt by most amateurs to some degree, but it does not necessarily diminish with experience. Some top pros have been troubled by it well into their careers. During a run of Othello, Laurence Olivier was so terrified of his soliloquies that he asked another actor to stand just offstage so he "would not feel so alone". Carly Simon used to stick pins in her hand before a performance to distract herself from her anxiety and once asked the entire brass section of the band to spank her just before the curtain rose.
Perhaps the problem faced by famous performers is that expectations are raised so high that they doubt their ability to live up to them. Once on the top of the pedestal the only way left to go is down.
Stage fright is part of the general fight/flight emergency system, which would have survival value if fighting or running away from an audience were appropriate. It is as though, in the human world, social isolation has such serious consequences that fear of sabre-toothed tigers has given way to a dread of public humiliation.
For our ancestors, being intently scrutinised was often a prelude to being eaten by a predator, hence our dread of losing the protection of the group. It is therefore important to keep a sense of proportion. The audience may kill us, but they almost certainly won't eat us.
Dr Glenn D Wilson is Visiting Professor of Psychology at Gresham College, where he was speaking last week