[Beldin]

Another hypothesis: being extravert means getting energised by interactions with others; being introvert means that costs energy. (Most people will have experienced both, at different times.)

This is why I don't think that being introvert is caused by fear, nor that courage cause extraverted behaviour. For most people, whether a social situation is providing or draining energy very often depends on more than just you.

Yes, there are exceptions. But don't underestimate yourself -- in either direction. The vast majority of people need both to thrive.

[nathan_compton]

> Another hypothesis: being extravert means getting energised by interactions with others; being introvert means that costs energy. (Most people will have experienced both, at different times.)

This isn't really a hypothesis so much as a restatement of the definition of each term. The person to which you are replying is giving a hypothetical explanation of _why_ the two conditions are the way they are.