The creators of these apes use a little cheat to help this process.
In contrast to normal apes, the movie primates have large whites around the iris of their eyes (sclera). If you look carefully at other animals, you will notice that humans are the only species to have this. We use the whites of the eyes to be able to judge the gaze direction of another person and thus infer valuable information about their emotions and intentions.
Having studied many hours of eye-tracking footage from advertising, I can't stress enough how important the eyes are to effective communication. If there is a human on the screen and that person is engaging the audience, then people will be looking up and down between their mouths and eyes, reading useful extra evidence into what the person is saying.
If the actor is providing a stoic, impassive performance, the audience's attention will stray to other elements of the scene. Engagement plunges, emotions flat line. You've lost your audience to the voyeuristic allure of their friends' superior Facebook existences.
Trust between humans is conveyed through the eyes.
People buy brands that they trust.
The eyes are the windows to your brand.
