Multitasking Lowers IQ
Research also shows that, in addition to slowing you down, multitasking lowers your IQ. A study at the University of London found that participants who multitasked during cognitive tasks experienced IQ score declines that were similar to what they'd expect if they had smoked marijuana or stayed up all night. IQ drops of 15 points for multitasking men lowered their scores to the average range of an 8-year-old child.
So the next time you're writing your boss an email during a meeting, remember that your cognitive capacity is being diminished to the point that you might as well let an 8-year-old write it for you.