It can be assumed that most people familiar with the video-sharing website YouTube have seen or at least heard of this popular video It is one of the most watched YouTube videos of all time, and in fact it can teach us a lot about the psychological development of infants.
In only 56 seconds viewers see a range of emotions displayed from Harry, age three, and Charlie, age one. In the beginning of the video, Harry shows happiness and is playful with his younger brother. Charlie displays interest in Harry's finger and turns his head toward his brother when he hears him talking.
Once Harry sticks his finger in Charlie's mouth, he is content but quickly his facial expressions show surprise and then fear and pain once his finger is bitten. Charlie then laughs at the camera, probably imitating his father's facial gesture as he was laughing while videotaping this. The viewer can see that Charlie is fixating on his father's eyes as he is videotaping. After watching this video one can see the broad range of emotions and reflexes that infants are capable of expressing.