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Abstract

Paternity uncertainty seems to have shaped humans' differential investment in kin. I examined sex differences in communication among nuclear kin to expand inquiry on this matter and address some methodological limitations in prior work. I analyzed data from national surveys in the USA and Spain and a study of mobile phone communication in the immediate aftermath of the 2013 Boston Marathon bombings. Respondents communicated mildly to moderately more with mother than father and more with sister than brother. The differences in communication with mother and father appeared in both subjective survey data and objective mobile telephone records. Across communication modes and studies, women and men did not differ consistently in overall frequency of communication. Matricentric and sororicentric tendencies were larger for the modes likely to involve dyadic communication (such as telephone calling and texting) than modes which often involve communication in group settings (face-to-face). The tendency to communicate more with female than male kin also appeared to be stronger in women respondents than in men. These results are consistent with paternity uncertainty as an ultimate evolutionary cause of differential investment in kin."The house does not rest on the earth, but on a woman." -Mexican proverb The Northeastern University Institutional Review Board approved the procedures for the national surveys and app study (approval #13-04-11). Respondents in the national surveys and app study gave their explicit informed consent with electronic responses before participating. All survey data delivered by YouGov and all app study data are non-identifiable. Analytic structure and measuresDyadic communication patterns within families can be summarized meaningfully only when the families included have similar family compositions. To examine sex biases in kin communication patterns within families, a respondent must have both male and female counterparts for a given role relationship. That is, for assessing sex biases in communication with parents, a respondent must have a living mother and a living father; for assessing sex biases in communication with siblings, a respondent must have a brother and a sister. Focusing comparisons on generic kin roles (e.g., parents, siblings) also eliminates confounding of communication patterns by generation. Similarly, I analyzed male and female respondents separately to isolate any biases in communication to the sex of the respondent's kin member.