Look around you in the office at lunchtime and you'll probably see at least one person cradling a phone in their shoulder whilst typing an email and eating a tuna sandwich (studies are inconclusive as to whether the flavour of the sandwich is important here). Being the busy and important people that we are, we multitask all the time, but unfortunately, we're pretty terrible at it.
Researchers have found that, on average, people in the workplace will tend to switch tasks every three minutes. Our brains are just not designed to handle this fickle approach to time management, causing an increase in stress levels and a decrease in productivity.
"But, hang on, I walk and talk all the time without having a nervous breakdown" you cry, hyperbolically. Well, yes, our brains are actually pretty good at handling multiple tasks when they are both ingrained, unconscious habits, such as riding a bike and shouting "look, no hands!" It is when one or both of the tasks require conscious effort that things tend to go awry - and anyone who has ever gotten stuck behind someone trying to walk and text at the same time will testify to that.