This idea was shared with me tonight by the mother of a 6-month old.

The Wonder Weeks is a book that describes the mental development of babies. In particular, it claims that mental development occurs in spurts ("leaps") that occur at precise periods after the due date of the child, and that in the week before such leaps, babies exhibit fussiness, in the form of clinginess, crankiness and crying.

From their site:

These difficult periods are usually accompanied by the three C’s: clinginess, crankiness and crying. We now know that they are the tell-tale signs of a period in which the child makes a major leap forward in his mental development.

Babies all undergo these fussy phases at around the same ages. During the first 20 months of a baby’s life, there are ten developmental leaps with their corresponding clingy periods at onset. The clingy periods come at 5, 8, 12, 19, 26, 37, 46, 55, 64 and 75 weeks. The onsets may vary by a week or two, but you can be sure of their occurrence.

Is it true that you can predict, to within a week, a prolonged period of particular baby fussiness, using this calendar?

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    It seems the initial study was done with a sample size of only 15 mother-infant pairs. What's impressive is the lack of any other serious study done on it (that I could find). Tons of mothers online claiming it worked for them, but nobody seems to be researching this. – Is Begot Jul 7 '14 at 3:19
  • @Geobits: I have heard similar claims from pretty much anyone having a child. My gut feeling is that it is mostly confirmation bias. Even the quote from the book says that "the onsets may vary by a week or two", which is A LOT when speaking of events in the life of an infant, which are supposed to be spaced only a few weeks apart... – nico Jul 7 '14 at 7:41
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    Interesting. I though it was because of teething, which would also fit description "The onsets may vary by a week or two, but you can be sure of their occurrence." – vartec Jul 7 '14 at 9:49
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    teething usually starts at 6 months. Doesn't explain the earlier periods. – HappySpoon Jul 7 '14 at 10:11
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