In an answer to my other question someone gave a seemingly good description of people with Down Syndrome but also stated that they "are incapable of getting angry."

http://answers.yahoo.com/question/;_ylc=X3oDMTE1MmI4N2IyBF9TAzIxMTU1MDAxMTgEc2VjA2Fu c19ub3QEc2xrA3N1YmplY3Q-;_ylv=3?qid=20080527225454AA4PLXO