Approaches to toilet training have fluctuated between "passive child readiness" ("nature"-based approaches), which emphasize individual child readiness, and more "structured behaviorally based" ("nurture"-based approaches), which emphasize the need for parents to initiate a training regime as soon as possible.: 4 : 216  Among the more popular methods are the Brazelton child-oriented approach, the approach outlined in The Common Sense Book of Baby and Child Care by Benjamin Spock, the methods recommended by the American Academy of Pediatrics, and the "toilet training in a day" approach developed by Nathan Azrin and Richard M. Foxx. According to the American Academy of Family Physicians, both the Brazelton and the Azrin/Foxx approaches are effective for developmentally normal children, although the evidence has been limited, and no study has directly compared the effectiveness of the two. Recommendations by the American Academy of Pediatrics follow closely with Brazelton, and at least one study has suggested that the Azrin/Foxx method was more effective than that proposed by Spock.