Humans imprint faces: I believe that humans imprint the faces of people they consistently look at from close range in the first year or so of life. I don't know exactly when the ability to imprint faces begins and ends, or how long the child must look at a face before it is imprinted. 

How to tell which faces are imprinted: 

1. To determine which faces are imprinted, compare your emotional reaction to pictures of people whose faces that could be imprinted - that is, people that you looked at a lot during your first year or so of life - to your emotional reaction to pictures of people whose faces could not be imprinted, such as a younger sibling, best friend, or spouse. An imprinted face will typically evoke a significantly different emotional reaction compared to a face that is not imprinted.

2. Listen to yourself complain about people. The complaints you make about people today, such as your boss, best friend, or lover, will also describe someone from your childhood whose face is imprinted. For details on this, see the Complaints page.