People check their smartphones a lot. One reason for this is that, in some way, it’s a gamble. You check your phone and maybe there are no notifications or maybe there’s a ‘red blob’. Maybe someone’s liked your Facebook post or someone’s ‘faved’ your Instagram picture of your brunch or your pet. Each time you get a notification, you feel happy: your brain releases a little bit of dopamine. So you wait a little while and you check your phone again, hoping for the same result and reinforcing the addictive behavior loop.