Again, this is taken from a post about Maria Konnikova’s book: Mastermind, How To Think Like Sherlock Holmes:

Holmes practices mindfulness, which sounds new-agey, but is actually quite practical. Mindfulness means focusing on only one problem or activity at a time. But mindfulness isn’t the opposite of multi-tasking, because there’s actually no such thing. “Our brain cannot do two things at once,” says Konnikova. “What we believe is multi-tasking is really the brain switching quickly from one task to the next.” And when our brains move so quickly between pursuits, it’s impossible to be truly focused on any single one. “Your attention is a finite resource,” says Konnikova. “Even when we’re walking down the street–not on the phone, not listening to music but simply thinking about what we’re having for dinner–we’re not really noticing the world around us.”

She points to a study from the National Academy of Sciences, which showed that people who described themselves as heavy media multi-taskers had much more trouble tuning out distractions than light media multi-taskers. They were also worse at switching between tasks. “So even though they were multi-tasking all the time, they were less efficient,” says Konnikova. She explains that our minds are programmed to wander, which multi-tasking exacerbates. But concentration is self-reinforcing. The more you do it, the better you get. “The more you learn to filter out irrelevant distractions, the better your brain can monitor [your] environment–both externally and internally.” This means that focusing on one activity or thought at a time will help you notice or remember details in your work, the things your read, and the people you talk to. This kind of focus will also make you better attuned to how you’re feeling, physically and emotionally.