The Guardian has an article by Daniel Levitan that describes the negatives of multitasking.
According to Earl Miller at MIT:
When people think they’re multitasking, they’re actually just switching from one task to another very rapidly. And every time they do, there’s a cognitive cost in doing so.
Why do we multitask when there’s this switching cost? Our brain releases opioids for the snippets of novelty associated with each individual task. And that could be more valuable to our brains, then the rewards of completing a single, longer task.
What’s worse, Russ Poldrack, does fMRI experiments at Stanford, and proposes that multitasking (er, watching TV) during study time could lead to suboptimal memory storage in the brain.
The rest of the article focuses on how our most accepted forms of communication (email, text) are inherently configured to promote multitasking and information overload. But there is one quote that sticks out in my mind:
‘When trying to concentrate on a task, an unread email in your inbox can reduce your effective IQ by 10 points.’