I do not agree too much with the link, as momof4 mentioned when parents play rough with a baby or let him pull hair he is absorbing everything. I have had bitters and I have suspected that it has something to do with it, but was not 100% sure. It was until I start reading from this group that I found that several people here with the same problem have found this cause in common. My own son was a bitter. Time out did not work at all. We have to talk about his feelings and feelings of the kids in pain. That all emotions are acceptable, but biting is not acceptable and guide him to acceptable behaviors. He was 18mos at that time. Even at the beginning I was getting blank stares and seemed as he did not understand, he actually did. And of course daddy stop playing rough and playfully pretend he was eating the baby.