The second of two programmes in which Matt and Emma Willis tackle the impact of smartphones on children's behaviour with a pioneering social experiment that sees a group of Year 8 pupils at the Stanway School in Colchester - and themselves - give up their smartphones for 21 days. This experiment, conducted in conjunction with the University of York, sees the pupils undergo a series of tests with experts, monitoring their behavioural changes over the duration, repeating the tests at the end of the three weeks to assess what effects giving up a phone has on the brain - including sleep and attention.