Serious Man but a Silly Woman?

I stumbled upon a very fun little test (actually, I found it here). It uses an algorithm based on identifying the frequency with which certain words are used in a text. It's supposed to tell you whether the author is male of female.

I ran a number of different blog entries through and got a mix of predicitons, some suggesting male authorship, others female. I noticed, though, I tended to get the male prediction when I was writing a more serious post and female when I was just being silly.

I wonder why that is?