Nicole Shanahan...formerly married to Google co-founder, Sergey Brin
Here's a real simple test you can do for yourself, if you have blue tooth head phones/earbuds try doing something that takes hand eye coordination that's not repetitive. Just going for a walk over uneven terrain all of a sudden becomes a bit more awkward and tests for the equilibrium more so when what once was just natural a natural reflex is slow to respond.. Next time do the same similar routine without the head set, it's not like you can plug in and unplug for most to notice the difference but some can.