Verified by 
Babies love faces. Newborns, for example, orient toward the face of the person holding them and the best focal distance for their eyes is the distance to that face. Within a few months, babies pay particular attention to eyes. Since the eyes are the window to the soul, children learn to look through that window. Children can see your emotions and they learn to see your thoughts through your eyes. By age 4, most children can perform some mind reading.
Human eyes are wonderful. Yes, it is nice to be able to see. But when I look at someone's eyes I can see amazing things. I can see emotion. I can also see where you are looking. Are you looking at me? If you are looking at me, then your irises are centered in your eyes and the whites are generally balanced. If you look away, the irises are not directed toward me and the whites become unbalanced. Adults can see immediately if someone is looking at them and that gaze has important consequences. In an fMRI brain scan study, Kampe and colleagues found greater stimulation in the brain reward areas when an attractive person's eye gaze was directed toward the camera (and thus toward the person inspecting the picture) than when the person was looking away. (You can see examples of the pictures they used. The key feature was whether the eyes, not the face, was oriented toward the camera.)
Sample pictures from Kampe et al.
Five month old babies also like being looked at. My colleague Larry Symons and his associates found that babies looked more and smiled more when the person they were interacting with was looking at them. Babies can notice even a small shift in gaze away from their faces. So the first point is that babies and adults notice and care if someone is looking them in the eyes. But this isn't mind reading yet.
Babies and young children also learn to track where we are looking when we look away. Within the first two years of life, children will start to turn in the same direction as the adult is looking and will eventually be able to look at the exact same object as the adult. This is generally referred to as triadic eye gaze. In triadic eye gaze, the observer sees that the other person is looking at an object and looks there too (2 people + 1 object = 3 things, thus triadic gaze). Triadic eye gaze probably underlies language learning. Adults and children can focus attention on the same object and then talk about it. Try getting your dog or cat to follow your eye gaze - they don't even really follow head orientation or finger pointing.
Between the ages of 3 and 4, children use triadic eye gaze to begin mind reading. At this age, most children realize that other people have minds, beliefs, and false beliefs. Children use eye gaze to determine another person's interests and desires. In another study, Symons (along with Lee, Eskritt, & Muir) found that 4 year olds could easily realize that someone wanted the object they were looking at. At younger ages, children can discern what someone is looking at, but they fail to realize this provides important information regarding the mind, interests, and desires of the other person. After age 4, children understand that other people look at the things that interest them.
A former student told me about her 3 and ½ year old daughter reading her mind. The young girl caught the mom looking at a cookie and asked, "Do you want that cookie, mommy?" The girl laughed and quickly grabbed the cookie. The daughter was right of course. The mom wanted the cookie, but her mind-reading daughter beat her to it!
Once children develop mind reading, the skill sticks around. You can see when someone has lost interest in talking with you. You can see who or what has attracted their attention. You can also get in trouble if your conversation partner sees that you are thinking about and are more interested in someone else. We can read minds because the eyes give us away. If you want protection from the mind readers, then wear dark sunglasses.
