Social anxiety has some similarities to performance anxiety. Certainly the physiological effects on our heart rate, stress hormones and ability to think are similar – but performance anxiety tends to occur in response to specific, high-stress events. Events that most of us would agree are anxiety producing – such as giving a speech at a wedding or being on stage.
Social anxiety, however, tends to involve more ordinary situations – a simple gathering of work colleagues, friends or family, just being watched sign a cheque, small talk in a queue. The very fact that the situations are ordinary – and the the anxiety not appropiate or proportionate – is part of the reason that the feelings cause such distress.
Performance anxiety does not require the existence of social anxiety.There are many celebrities that suffer with almost uncontrollable performance anxiety (stage fright) but have no other anxiety symptoms or issues.
Similarly there are some with social anxiety – apparently many entertainers – who are full of confidence on TV, radio or stage but have social anxiety in other more ordinary scenarios. e.g. Rhod Gilbert radio interview about the BBC documentary Standing up to Shyness.