We humans like to think of ourselves as having free will. We like to think, for instance, that how many sexual partners we have and how quick we are to jump into bed with someone is all a matter of personal choice, right? But what if this wasn't entirely true? What if I said there might be microorganisms that enter our bodies, "hijack" our brains, and direct our behaviors (sexually and otherwise) for their own purposes (e.g., to spread to other persons and reproduce)? I know--you'd probably think I've been watching too many science fiction movies. However, this concept actually isn't that far-fetched. In fact, some research suggests that this very thing actually happens in the animal kingdom.

As some evidence of this, check out the fascinating TED Talk below entitled "Zombie Roaches and Other Parasite Tales" by science writer Ed Yong. In it, he provides provocative (and disturbing) examples of how a parasite can manipulate a host's behavior in dramatic ways. After you watch it, check out this equally fascinating (and disturbing) article on how a certain sexually transmitted infection (STI) in crickets seems to wield a powerful influence over their mating behaviors in a way that appears to help the infection spread more easily. Although we don't have any conclusive evidence yet that STIs or other infections can take over humans in the same way, we also can't completely dismiss the idea either.