title: Secular trends and individual differences in toilet-training progress.
mesh_terms: D002657:Child Development; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D012737:Sex Factors; D012890:Sleep; D012951:Socialization; D014039:Toilet Training