Nontaster
A nontaster is a person who reports no taste sensation when exposed to a chemical called propylthiouracil (PROP). This chemical causes a severe bitter taste for some individuals, a mildly bitter taste for some, and no sensation at all for others. According to a study performed by Dr. Linda Bartoshuk in 1991, this nontaster reaction is caused by a lack of what is called the PROP receptor in a person's mouth.