The Olive Theory.

thefiero:

Eyetrackshop a start up that run eye-tracking tests on websites has been helping Mashable analyze point of interests on the major social media players. 

The tests are done using a webcam to track eye movements. As you can see, for Facebook, viewers eyes directly go straight into profile picture, down to recent content, and right onto mutual friends. LinkedIn on the other hand, has their focus on job titles before profile pictures.