Experimental Evidence for Grandmothers’ Differential Investment in Grandchildren
Grandparental investment, which is a worldwide phenomenon, is relatively neglected by Asian researchers. Although the amount of research on grandparental investment in Europe and Northern America has been increasing, there is less research on how grandchild factors influence grandmothers’ investment in grandchildren. Drawing on sex chromosome relatedness theory and the hypothesis about phenotypic similarity cues, we designed an experiment to test how two grandchild factors (sex and resemblance) influence grandmothers’ biased investment. In the experiment, 80 childless female undergraduates (M age = 19.62 years) who had to imagine being a grandmother were presented with an array of children’s faces (which had been morphed to resemble theirs to varying degrees) and were asked to make hypothetical grandparental investment decisions. We showed that (1) hypothetical paternal grandmothers were more likely to invest in granddaughters than hypothetical maternal grandmothers; and (2) hypothetical paternal grandmothers were more likely to favor self-resembling grandchildren than hypothetical maternal grandmothers. These findings extend existing evolutionary accounts of grandparental investment by specifying how grandchild factors influence grandmothers’ investment.
KeywordsGrandparental investment Grandmothers Sex chromosome relatedness Resemblance
This study was supported by National Natural Science Foundation of China (31500901) and the general support from the research fund of the School of Social Development and Public Policy at Fudan University.
Compliance with Ethical Standards
The authors declare that they have no conflict of interest. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.
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