This is Hidden Brain. I'm Shankar Vedantam.

When David Pizarro was five years old, he was at a weekly church meeting with his family.

The grown-ups went to visit with each other while the children, including David, were left to their own devices.

And my sister and her little friend thought that they would play a fun game with me,

and that game involved making me lie down, close my eyes, and open my mouth.

They wouldn't tell David what was going to happen.

It was to be a surprise.

I sort of naively trusting of my dear older sister, who by the way is an attorney now,

sure enough, closed my eyes and opened my mouth. And I felt something soft, wet, and sort of cold

in my mouth. And I immediately spit, opened my eyes, and I saw my sister and her little friend

laughing.

If you're eating something right now, I'd advise you to put it down.

What they had put in my mouth was, I don't recall exactly what food it was, but it was partially chewed food

that the other little girl had decided to chew up, put in her hand, and then stick right in my

mouth.

David's sister and her friend thought the whole thing was hilarious.

I've never felt so betrayed.

This is one of the key moments in my life where I was so disgusted.

I don't remember throwing up, but I can tell you for sure that I felt like throwing up.

And I, to this day, can remember the texture, the temperature, the feeling of that food in my mouth.

Wow.

As you're telling the story, I have to confess, I can feel my stomach turning here, David.

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