The bacteria living in your gut may influence your personality. The top row of the graph tracks the movement of a mouse with normal gut bacteria (“SPF” means “specific pathogen free”) as it scurries around in an open arena over the course of an hour. The bottom row tracks the movement of a mouse that grew up without gut bacteria (“GF” means “germ free”). This little dude is much more active towards the end of the hour. Read about how gut bacteria influence brain development and personality in mice by clicking on the image.