crawl: The age at which babies start to crawl

crawlR Documentation

The age at which babies start to crawl


The age at which babies start to crawl, the birth month and average monthly temperature six months after the birth month




A data frame with 12 observations on the following 5 variables.


the baby's birth month; levels such as January and July


the mean age (in completed weeks) at which the babies born this month started to crawl; a numeric vector


the standard deviation (in completed weeks) of the crawling ages for babies born this month; a numeric vector


the number of babies in the study born in the given month; a numeric vector


the monthly average temperature (in degrees F) six months after the birth month; a numeric vector


The data come from a study which hypothesized that babies would take longer to learn to crawl in colder months because the extra clothing restricts their movement. From 1988–1991, recorded were the babies' first crawling age and the average monthly temperature 6 months after birth (when “infants presumably enter the window of locomotor readiness”). The parents reported the birth month, and age when their baby first crept or crawled a distance of four feet in one minute. Data were collected at the University of Denver Infant Study Center on 208 boys and 206 girls, and summarized by the birth month.


Janette Benson (1993) Season of birth and onset of locomotion: Theoretical and methodological implications. Infant Behavior and Development, 16(1), 69–81.

Thanks to Janette Benson for granting permission to use this data set.


plot(Age ~ Temp, data=crawl, cex=0.05*SampleSize, pch=19)

GLMsData documentation built on Aug. 22, 2022, 9:10 a.m.

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