Parental Speech and Gesture Input to Girls Versus Boys in Singletons and Twins

Children show sex differences in early speech development, with girls producing a greater number and variety of words at an earlier age than boys (Berglund et al. in Scand J Psychol 46(6): 485–491, 2005)—a pattern that also becomes evident in gesture (Butterworth and Morisette in J Reprod Infant Psychol 14(3): 219–231, 1996). Importantly, parents show variability in how they produce speech when interacting with their singleton sons vs. daughters (i.e., Cherry and Lewis in Dev Psychol 12: 278–282, 1976; Leaper et al. in Dev Psychol 34: 3–27, 1998). However, it is unknown whether the variability in speech input extends to different twin dyads or becomes evident in gesture input. In this study, we examined parental gesture and speech input to 35 singleton (19 boys, 16 girls) and 62 twin (10 boy–boy, 9 girl–girl, and 12 girl–boy dyads) Turkish children (age range = 0;10–3;4) in parent–child interactions. We asked whether there is evidence of sex (girls vs. boys) or group (singletons vs. twins) differences in parents’ speech and gesture production, and whether these differences also become evident in different twin dyads (girl–girl, boy–boy, girl–boy). Our results, based on parent-child interactions, largely showed no evidence of sex or dyad-composition difference in either parent speech or gesture, but evidence of a group difference in gesture, with the parents of singletons providing a greater amount, diversity, and complexity of gestures than parents of twins in their interactions. These results suggest that differences in parent input to singletons vs. twins might become evident initially in gesture.