http://cep.lse.ac.uk/conference_papers/22_09_2006/KahnemanFinal.pdf
A rather larger difference was observed in the enjoyment of child care and of interactions with children. The American mothers spent more time focused on child care (18% vs. 14% of the waking day), but enjoyed it less. In the standardized units that were used in Table 2, the mean of Difmax during childcare is -.22 in Columbus, .09 in Rennes (t = 2.76). The difference in the enjoyment of children spills into the response to family occasions. Women in both samples enjoyed one-on-one interaction with their spouse about equally (Difmax averages were .32 and .33), but the corresponding values when children were present were -.05 and .22, suggesting that the presence of the spouse hardly makes American children less annoying to their mother. The relative unhappiness of American mothers obviously demands further study. Our French team member suggested that French children are simply better, but other hypotheses should also be considered.