Here is a nice bit of reference, for animators and film makers alike, with research showing what the typical viewer looks at.
Below is an excerpt from There Will Be Blood (Paul Thomas Anderson, 2007). 11 adult viewers were shown the video and their eye movements recorded using an Eyelink 1000 (SR Research) infra-red camera-based eyetracker. Each dot represents the center of one viewer’s gaze. The size of each dot represents the length of time they have held fixation.
It really shows how important it is to give our characters a thoughtful performance, and how we should keep them alive even if they aren’t the ones delivering dialogue.
Click the player below and enjoy the video: