Our brains are adapting to typing with our thumbs11
Using electrodes and EEGs to monitor brain activity, the study found that the smartphone users had different responses than the older cellphone users. 62 electrodes placed on the test subject's heads monitored their movement of the thumb, forefinger and middle finger. Cortical brain activity in the part of the brain that deals with control of the thumb was higher in smartphone users. And the more time that the smartphone users spent with their devices, the stronger that signal was.
The bottom line is that using your thumb to type on your smartphone is similar to learning how to play the violin. Your brain responds to both tasks by increasing cortical brain activity for the appropriate part of your body. For violinists, the brain has increased cortical activity in the fingers. Among smartphone users, the increased cortical activity is seen in the part of the brain that controls your thumbs.
source: EurekAlert! via TechCrunch