Knowing how to easily manipulate the people around you. Not exactly a good thing though.
Harry Frederick Harlow was a psychologist known for his studies on rhesus monkeys. The study focused on maternal separation, social isolation and dependency. The most helpful thing a person can do for a frightened infant or child is to promote classical conditioning to avoid separation anxiety.
Agreement or concord happens when a word changes form depending on the other words to which it relates. It is an instance of inflection, and usually involves making the value of some grammatical category "agree" between varied words or parts of the sentence.