Mothers’ fathers consistently invest more in their grandchildren than fathers’ mothers. This pattern was explained by Laham et al. in Personality and Social Psychology Bulletin , 31(1), 63-72. (2005) via the preferential investment hypothesis—the idea that fathers’ mothers invest less in grandchildren than mothers’ fathers because the former typically have more certain alternate investment outlets available. In two studies of prolific workers (combined N = 4086), we first failed to replicate the findings of Laham et al. and then successfully replicated them. In the combined sample, mothers’ fathers received more positive ratings than fathers’ mothers when participants had cousins through fathers’ sisters, but this difference between grandparents disappeared when participants did not have cousins through fathers’ sisters. We also found that people spent more time with their maternal and paternal grandparents to the degree that they were not maternal grandparents to someone else, which mediated the closer feelings.

与父亲的母亲相比，母亲的父亲对孙辈的投资始终如一。Laham 等人解释了这种模式。在人格和社会心理学公报，31（1），63-72。（2005 年）通过优惠投资假说——父亲的母亲对孙辈的投资少于母亲的父亲，因为前者通常有更多确定的替代投资渠道可用。在多产工人的两项研究中（结合N = 4086），我们首先未能复制 Laham 等人的研究结果。然后成功复制它们。在合并样本中，当参与者通过父亲的姐妹有堂兄弟姐妹时，母亲的父亲比父亲的母亲得到更多的正面评价，但是当参与者没有通过父亲的姐妹有堂兄弟时，祖父母之间的这种差异就消失了。我们还发现，人们花更多的时间与他们的外祖父母和外祖父母在一起，以至于他们不是其他人的外祖父母，这调节了更亲密的感情。