Cortex Scan is a common mental ability.
Cortex Scan allows the user to read the thoughts of others, including other Furons. This is used for gathering important information, and others just for random humor.
By reading human minds, Crypto also drains concentration energy from the minds he scans. The energy he takes is used to replenish his own mental strength in the first game, which lets him maintain his Holobob disguise longer. It can also work the same way in Path of the Furon when in Body Snatch mode, reading minds replenishes the possessed body's health meter.
In the second game, this ability can only be used while in Body Snatch mode to gather important information, but in no way does it help the player stay in disguise longer.