Young people: what rules around smartphone use should be put in place for children?

We would like to hear from people aged 18-24 about their childhood experiences with smartphones - positive or negative

We would like to hear from people aged 18-24 about their childhood experiences with smartphones and social media, positive or negative.

What approach would you take with your own children, as a result of lessons learned from your experience? Would you let them have access to a smartphone or social media, and how often? What rules would you put in place?