Introvert or extrovert, normal or abnormal: the problem with personality types

The idea that people can be classified into types has a long history. Writing 23 centuries ago, the Greek philosopher Theophrastus sketched 30 characters that are instantly recognisable to this day. They include the chatterbox, the back-biter, the ungrateful grumbler, the penny-pincher and the patron of rascals. This ancient attempt to sort people into types [...]