So it takes a study of 19,000 children to show that smacking leads them to struggle with exams (Report, 11 June). Probably true, but the main lesson they learn is that violence can fix a problem provided you are bigger and stronger than your opponent. A message picked up in the kindergarten and carried as far as the White House.
Geoff Wheeler
Balsall Common, West Midlands
• Your article had an interesting but only a partial analysis of bacterial safety (Is it true that … you have five seconds’ grace after dropping food on the floor?, 15 June). The full rule is “Pick it up within five seconds and then blow on it.” It’s the combination that works.
Malcolm Mitchell
Harrow, London