Are Wednesday’s children full of woe? Children’s differences in physical and psychological traits are independent of day of birth

Nursery rhymes are rich in alliteration and vocabulary, and their benefits for children’s language and literacy have been widely studied. Less is known about the influence that nursery rhymes’ messages may have on children’s development. Here, we focused on ‘Monday’s Child’, a popular nursery rhyme which alleges that the day of the week of children’s birth forecasts their differences in physical and psychological traits. Data came from E-Risk, a UK-population representative, longitudinal cohort study of 1,116 families, whose same-sex twin children were assessed at ages 5 through to 18 years (with 93% retention). In our preregistered analyses, being born on Monday through Saturday did not predict children’s physical and psychological traits as implied by the ‘Monday’s Child’ rhyme (β = -.04 to .03; 95%CI = -0.10 to 0.09; p = .195 to .754). Being born on Sunday was also not associated with children’s traits across measures (β = -.00; 95%CI = -0.05 to 0.05; p = .945). Results were unchanged after covariate adjustment (i.e., children’s sex, birthweight, and socioeconomic status). Our findings suggest that children’s differences in physical and psychological traits are independent of the day of the week of their birth, refuting the messages from ‘Monday’s Child’ nursery rhyme.