The scientifically un-rigorous interpretation on my part is that women instinctively lie about sex much more than men. This is quite understandable as a woman's survival in the ancestral environment was most often about how effectively she capitalized on her sex appeal. This would involve pretending to be more aroused in situations where she was expected to be aroused (i.e. an alpha male wants her to be aroused) and not showing signs of arousal in situations where she shouldn't (don't let the alpha male see you lusting after a different male).

Now the fact that women responded to a broader range of pictures than men I have no ideas about. Perhaps it is not an adaptation but merely a side effect of women being more empathetic. Do women have more/more highly reactive mirror neurons? Have any studies been done on this?