Are there sex differences in temperament?
It depends in part on age. Our research at Kaiser Permanente found that at 4 months, baby girls were significantly more sensitive and fussy about wet diapers.
Girls rated at 4 months as easily frustrated and bothered by new things, were more likely in later months to be shy and fearful in strange places and to have more difficulty with sleep and separation. The same did not hold true for boys. On the other hand, more active 4-month old boys were more likely, as they grew, to resist being confined as in a playpen. This was not the case with girls.
Other researchers have found that though there is much variation among both boys and girls, girls tend to have more negative emotions during the teens. Over the long haul, girls in general have a little more attention and impulse control. Over time, boys in general have somewhat more energy and a tendency to seek more risk. There are, of course, both boys and girls who do not fit the general patterns.