According to Daniel Pocock’s talk at DebConf17’s Open Day, hearing a ping from your messaging or e-mail app or seeing a visual notification of a new unread message has an equivalent effect on your ability to concentrate as

• a 10 point drop in your IQ; or

• drinking a glass of wine.

This effect is probably at least somewhat mitigated by reading the message, but that is a context switch, and we all know what those do to your concentration. So if you want to get anything done, be sure to turn off notifications.