Self-guided experience "trains" many people, and some of them infer a rule that double clicking is for opening things. Older people especially can fail to notic

Self-guided experience "trains" many people, and some of them infer a rule that double clicking is for opening things. Older people especially can fail to notice that many widgets respond to their first click and continue with the same action on the second click, so their behavior doesn't stand much chance of correction.