This article appeared in the September/October 2021 issue of Discover magazine as "Not Set in Stone." Become a subscriber for unlimited access to our archive.
If you were a rat, the smell of cat urine would likely scare you as much as a rattlesnake’s hiss. But the rat navigating a maze for Joanne Webster, pathobiologist at London’s Royal Veterinary College, was no ordinary specimen. As it explored the labyrinth that stretched ahead — cautiously, at first, then more boldly — the rat stumbled upon a strange smell wafting from one of the corners. The scent seemed to draw it in.
What the rat found so tempting, as did many of his labmates tested in the maze, was indeed cat urine — turned, somehow, from rodent repellent to love potion. The rats had previously been infected with Toxoplasma gondii, a brain parasite that, as the scientists running the trials were learning, considerably altered the way the rats behaved. Not only did they display this potentially fatal, certainly ill-advised feline attraction, but they were also more eager to explore the maze than uninfected animals were. For better or for worse, their rat “personality” had changed towards a higher level of openness to experience.
Research shows that human personality can change, too, sometimes even dramatically — and not just because of a parasitic infection. In fact, personalities can fluctuate with age, shift because of life events and even change due to things we ingest. What’s more, we can actually alter our personalities with our own efforts, and making those changes may be simpler than we think.
