Your Baby’s Fussy Phases

Babies grow and develop at an astounding rate, but it turns out that those developmental leaps happen at specific times, following some not-so-sunshiny days. Listen to Dr. Frans Plooij, creator of The Wonder Weeks, explain what the fussy phases are all about, how to tell they are happening, and what you can do about it.


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What we talked about:

  • What do chimpanzees have to do with this?
  • Learn the three C’s to know when a leap is happening
  • How long do the leaps last?
  • Do these fussy periods coincide with growth spurts?
  • How are moms, dads, and other caregivers affected?
  • What are the phases of a mental leap?
  • How to help yourself to make it through a leap
  • Why gestational age matters


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Courtesy of Dr. Frans Plooij

About Dr. Frans Plooij

Born in 1946, Frans X. Plooij is an Dutch ethologist with a background in Educational Psychology, Physical Anthropology and Behavioral Biology. He studied in the Netherlands with Adriaan Kortlandt, University of Amsterdam, with Hein Oomen, University of Nijmegen, and with Gerard Baerends, University of Groningen, where he received his Ph.D. in 1980.

In 1971–73, he and his wife Hetty van de Rijt worked with Jane Goodall in the Gombe National Park, Tanzania, East-Africa, on infant development in free-living chimpanzees. In 1973-76 he worked with Robert Hinde in the Medical Research Council unit on the Development and Integration of Behaviour, University Sub-department of Animal Behaviour in Madingley, Cambridge, England; in 1976-80 at the department of Developmental Psychology, University of Nijmegen, the Netherlands; and from 1981 to 1993 as head of the department of Research and Development at the institute for Child Studies of the City of Amsterdam, the Netherlands, where, among other things, he participated in European Union SOCRATES-LINGUA projects concerning the implementation of an innovative second- and foreign-language teaching method for small schoolchildren.

From 1993 to 1998, he was a professor at the Department of Developmental and Experimental Clinical Psychology, University of Groningen.

He is currently president of the International Research-institute on Infant Studies (IRIS) at Arnhem, the Netherlands, initiator of the European project on “the intercultural study of infantile regression periods” (ISIRP), and director of Kiddy World Promotions B.V., a consulting firm that serves companies producing products related to children, such as toys.

Dr. Plooij was Vice-president for Information of the International Society for Human Ethology from 1989-1993, Vice-president of the Institut Européen pour le Développement de tous les Enfants (IEDPE), served on the editorial board of the journal “Ethology and Sociobiology”, and was member of the panel of assessors of the Journal of Clinical Child Psychology and Psychiatry.

He is a full member of several international, scientific societies in the domains of child development and behavioral biology, and of the New York Academy of Sciences.

In addition to numerous scientific publications, Dr. Plooij has written several best-selling parenting books, one of which, The Wonder Weeks, has been published in many languages, from the USA to Japan. The Wonder Weeks became a Worldwide bestseller on infant development and has sold over 1.5 million copies!

Head to to connect with Dr. Frans and become part of the Wonder Weeks community.

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