People can multitask perfectly fine when the tasks they are doing are automatic (that's why you can usually drive and have a conversation [with a passenger] at

People can multitask perfectly fine when the tasks they are doing are automatic (that's why you can usually drive and have a conversation [with a passenger] at the same time without any difficulty). When you're doing multiple things that require cognitive resources, your brain has to share its (surprisingly limited) short-term computational power/memory, resulting in decreased performance. There aren't many things people do on computers that are automatic (at least not many things I do). But I'm typing this on a computer with three monitors, and I can say objectively that my efficiency is way higher than if I had one small screen with at least two clicks to get to my next app.