Context switches are expensive for human brains and even though many managers (other people too, but managers definitely) have convinced themselves that they can easily handle a multitude of tasks at the same time (e.g. take a second call and answer emails while in a meeting) the truth is they will underperform at all of them without noticing (oh, and by the way: I’m sometimes guilty of that myself).
The solution to that sounds pretty simple: Concentrate on one thing at a time. If your meeting is boring you should probably leave it and give your full attention to something else. But the poison that kills this idea are notifications. They interrupt your current thought and draw your attention towards something that might be completely unrelated to what you did before (and not at all that urgent and important for the most part). And worst of all: Application developers love notifications and they think their application is the most important of all and should definitely notify you, so the default is to notify the user of everything all the time. As a result, if you don’t actively disable notifications and use several applications, you will soon have a lot of notifications.
That’s why I can only encourage you to turn off all of your notifications, because then you decide when to look at an app whether there is any relevant news. All notifications? Well, probably not all all. At work, I have my email notifications disabled completely whereas sound notifications for chat and calls are enabled unless I’m working on a special focus topic. Oh and I think popup notifications are the worst of the pack so that’s the first thing I turn off entirely when I install something. On my phone, all sound notifications are off all the time and vibration notifications are only on for calls and chats with the most important people. I look at my phone and mails regularly so I still have a pretty reasonable response time, but this way I can decide when I do that without interrupting any other thoughts.