it is easier to find an adventurous girl than a sissy boy. The bucking of gender stereotypes in young children’s books is a task usually performed by female characters, many researchers have found. Just as in the real world women have been quicker to forge forth into the masculine world of work than men have been to sink back into domesticity, in children’s books, too, it is mostly females who do the crossing of gender boundaries.
More on that 'sissy' trend. Does anyone have a better word than that, by the way? It's very pejorative.