如果你觉得自己跟外婆比跟奶奶亲，纽卡斯尔和安特卫普大学的研究人员并不会感到惊讶。他们根据在荷兰进行的研究宣称，在与孙辈保持经常联系方面，外公外婆可能会比爷爷奶奶付出更大的努力。

If you feel you have a closer relationship with your granny on your mother’s side than on your father’s side, it is no surprise to researchers at the universities of Newcastle and Antwerp. Based on studies in the Netherlands, they claim that maternal¹ grandparents are likely to make greater efforts to maintain frequent contact with their grandchildren than paternal² grandparents.

他们推测，这是人类进化相关心理机制在起作用。这些研究人员指出，由于母性的缘故，女性总是对自己与儿女的关系非常确定，而男性从来不能完全确定自己是否是子女的生父。

They speculate that psychological mechanisms³ related to human evolution are involved: women, because of maternity⁴, are always sure of their relationship to their sons or daughters, whereas men can never be wholly certain they are their children’s biological fathers, they suggest.

此外，就与孙辈关系而言，外公外婆总是比爷爷奶奶更为确定。“因此，外公外婆（尤其是外婆）可能会多走一些路，去看望孙辈。”

Furthermore, maternal grandparents are always more certain than paternal grandparents that a grandchild is related to them: “Thus maternal grandparents, especially maternal grandmothers, may go the extra mile to visit their grandchildren.”

托马斯?波莱(Thomas Pollet)及其同事进行的这项研究发现，对于生活在孙辈30公里以内的祖父母而言，超过30%的外婆和25%的外公每天或者每周几次与孙辈接触。相比之下，对爷爷奶奶而言，这一比例则降至15%。

The study, carried out by Thomas Pollet and his colleagues, found that for grandparents living within 30km of their grandchildren, more than 30 per cent of maternal grandmothers and 25 per cent of maternal grandfathers had contact daily or a few times a week. In contrast, this fell to 15 per cent for paternal grandparents.

波莱表示：“即便是在离婚的家庭，我们也发现了一致的差异。外公外婆付出的努力更多。”

Mr Pollet said: “Even in families where there has been divorce, we found consistent differences. Grandparents on your mother’s side make the extra effort.”