The trendy consensus is that smartphones have had a negative effect on social relations. I don’t have any data to hand, but my anec-data don’t totally support this.
Let’s say you have two people together in a bar/restaurant, and both are looking at their phones & not talking to one another - for whatever reason. I think it’s a stretch to say that if mobile phones didn’t exist these two would be engaged in lively, witty discourse - and that the only thing keeping them apart is modern technology. On the contrary, I’d assume that these people are either both preoccupied with something, or that they don’t enjoy each other’s company - taking their phones out of the equation won’t help to improve conversation, it will just make things tense or awkward.
Perhaps there are certain situations where strangers are together in public (such as waiting for a bus, or in a dentist’s waiting room) when pre-mobile phones people would talk to each other (out of boredom, perceived social necessity or whatever), but now people do not. Having grown up in the south-east of England, however, I have never had much first-hand experience of this. As I recall, strangers talk to each other in public nowadays just as much as they did 10-20-30 years ago. In the old days people read newspapers or whatever to pass the time in public places, now they read their phone screens.
If anything, mobile phones have a mild social catalyst effect. Now, when I am talking to someone I know I can show them photos of my family/play funny videos/share music etc…; this adds to the social experience - if anything, smart phones enrich conversation - or at least they certainly have the potential to.
I work with teenagers, and it is true that they are on their phones a lot. But, they are invariably communicating - albeit in ways and with codes and protocols which are quite alien to adults. Do they spend more time on their phones - and therefore spend less time on face-to-face contact - than teenagers 20 years ago? Perhaps, but it would be wrong to describe them as anti-social (if anything, today’s teenagers are hyper-social - they probably communicate more things to more people than any other generation in history). Plus, it would (again) be wrong to assume that if you had a group of teenagers all playing with their phones, and all of a sudden said phones vanished, that they would magically start talking to one another. In my teenage years my friends and I spent many an hour not really talking or doing anything in each other’s company. Smartphones would have enriched our social lives, not impoverished them.
Long story short, people prioritise between their phones and the people that they are physically with. Sometimes, the phone takes priority over the other person - this isn’t necessarily something to lament - there are many perfectly good reasons for it. In the old days we didn’t have that choice; now we do.