
This book derives from almost five decades of research, beginning at first with ethological observation of free-living chimpanzee mothers and infants undertaken in 1971 in cooperation with Jane Goodall, and then extending to more elaborate research with human mothers and infants. These correspond to successive developments in the growing brain, as manifested in the child's ability to perceive and then to control a new kind of perceptions at a higher level of the perceptual hierarchy. Claims Īccording to the book, babies go through 10 predictable 'leaps' in their cognitive development during the first 20 months of life.

The book continues to be popular, and the publisher has produced a mobile app based on the book. The research has been replicated several times, and Brazelton found it to be mutually confirmatory with his own work. Questioning of the research with mother-infant dyads has received some attention in the press and social media, though sometimes reducing it to a matter of sleep schedules. Its theoretical basis is Perceptual Control Theory, which predicts and explains the observed phenomena. Drawing on many years of observation and analysis of infant development, it gives parents practical guidance to help their baby's cognitive development through its predictable stages or 'leaps'. Originally published in 1992, it has been republished several times, with an updated 6th edition published in 2019. The Wonder Weeks is the English translation of the Dutch book Oei, ik groei! (literal translation: Ai, I'm growing!) by physical anthropologist Hetty van de Rijt and ethologist and developmental psychologist Frans Plooij.

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