THERE MAY BE NOTHING more self-defining than our

tastes. Whether in food, wine, romantic partners, or

political candidates, our tastes represent our identity.

So it made sense to me that my likes and dislikes were

formed through careful deliberation and rational

decision-making—that is, through choices where

I wielded some control.

Then I became acquainted with Toxoplasma

gondii. In my research at the Indiana University

School of Medicine, I observed how the single-celled

T. gondii parasite can change the behavior of the host

it infects. It can make rats unafraid of cats, and some

studies show that it may cause personality changes

(such as increased anxiety) in humans.

These studies made me wonder if there are other

things happening under our radar that could be

shaping who we are, programming our likes and

dislikes. As I dug into the scientific literature, I hit

upon this astonishing and unsettling truth: Our

BY BILL SULLIVAN

THINK YOU HAVE GOOD TASTE? YOU DON’T DESERVE THE CREDIT.

THANK YOUR GENES, YOUR GERMS, AND YOUR ENVIRONMENT.

T

IN THIS SECTION

Jupiter’s close-up

Cheese with a beat

A squirrelly color

Language integration

THE DISCOVERIES OF TODAY THAT WILL DEFINE THE WORLD OF TOMORROW

NATIONAL GEOGRAPHIC VOL. 236 NO. 3

EMBARK

Why You Like

What You Like