We have not yet begun to scratch the surface of how pathogens and other bugs can manipulate behavior. This is also a major cost of infection that many people don’t even consider; our personalities are no doubt shaped in part by our current and past infections and our microbiome.
In The Selfish Gene, Dawkins speculates that sexually transmitted infections, in order to spread as far and wide as possible, could increase the libidos of their hosts:
I do not know of any direct evidence that sexually transmitted diseases increase the libido of sufferers, but I conjecture that it would be worth looking into. Certainly at least one alleged aphrodisiac, Spanish Fly, is said to work by inducing an itch . . . and making people itch is just the kind of thing viruses are good at. (Dawkins 2006 pg. 247)
A bright woman of ninety, Natasha K., recently came to our clinic. Soon after her eighty-eighth birthday, she said, she noticed ‘a change’. What sort of change? we queried.
“Delightful!’ she exclaimed. ‘I thoroughly enjoyed it. I felt more energetic, more alive—I felt young once again. I took an interest in the young men. I started to feel, you might say, “frisky”—yes, frisky.’…
The mirror test is used to gauge self consciousness by ascertaining whether an organism can identify itself in the mirror. Usually, the experimenter puts some kind of ink or marking in a spot that can’t be seen without a mirror and then observes the animal. Examining or touching the spot or marking indicates that the animal knows the image is, in fact, not another individual but a reflection. Richard Byrne spoke about the mirror test last week at his talk at Portsmouth and showed us that elephants can recognize themselves in a mirror (or at least one elephant can, the other apparently showed no interest). He also told us that dogs and cats cannot recognize themselves in the mirror but eventually acclimate to having an intruder around all the time who they cannot smell.
When I was last in the States I was at a pet store and saw the betta fish display. Bettas, otherwise known as “Siamese fighting fish”, are colorful, aggressive, territorial fish that will display when put in proximity to other fish. Like many territorial species the males will size each other up with aggressive displays and it’s in both males’ interests if they can figure out who would win without actually fighting. Many places that sell Bettas put these fish close together where they will display all day to one another ultimately stressing them out and potentially reducing their longevity. Often Bettas will be put in front of mirrors which will get them really geared up as they prepare to fight a rival who is equally matched on all dimensions of strength, size, vigor, and display.