Couples with little or no education use NFP successfully. The NFP methods are so simple that they are successfully used by couples of various cultures and educational backgrounds all around the world. (Kambic and Gray, Human Reproduction, 1988, p. 693). The blind use NFP effectively. During the NFP classes, couples are taught to recognize signs of fertility and infertility. With some NFP methods couples are also taught to read, record, and interpret temperatures.