Are some ideas so dangerous we shouldn’t even talk about them? That question brought Radiolab’s senior editor, Pat Walters, to a subject that at first he thought was long gone: the measuring of human intelligence with IQ tests. Turns out, the tests are all around us. In the workplace. The criminal justice system. Even the NFL. And they’re massive in schools. More than a million US children are IQ tested every year.

We begin Radiolab Presents: “G” with a sentence that stopped us all in our tracks: In the state of California, it is off-limits to administer an IQ test to a child if he or she is Black. That’s because of a little-known case called Larry P v Riles that in the 1970s put the IQ test itself on trial. With the help of reporter Lee Romney, we investigate how that lawsuit came to be, where IQ tests came from, and what happened to one little boy who got caught in the crossfire.

This episode was reported and produced by Lee Romney, Rachael Cusick and Pat Walters.

Music by Alex Overington. Fact-checking by Diane Kelly.

Special thanks to Elie Mystal, Chenjerai Kumanyika, Amanda Stern, Nora Lyons, Ki Sung, Public Advocates, Michelle Wilson, Peter Fernandez, John Schaefer. Lee Romney’s reporting was supported in part by USC’s Center for Health Journalism.

Radiolab’s “G” is supported in part by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science.

Support Radiolab today at Radiolab.org/donate.