For many years the psychology research has shown that people can only attend to one task at a time. Let me be even more specific. The research shows that people can attend to only one cognitive task at a time. You can only be thinking about one thing at a time. You can only be conducting one mental activity at a time. So you can be talking or you can be reading. You can be reading or you can be typing. You can be listening or you can be reading. One thing at a time.

https://www.blog.theteamw.com/2009/11/03/100-things-you-should-know-about-people-7-people-cant-multi-task/