I've taken 2 cog tests..one for Eagle, one for Comair. They test accuracy under pressure, multi tasking, visualization, short term memory, visual coordination, etc....all of which are desirable in a pilot candidate. It's all silly if you ask me, though. A cockpit is a whole different environment. Someone who does well on the Cog, might suck in the air and visa versa. Just my humble opinion.
Seems like they test how much practice I've had playing Sega (8 bit old school) or Atari...