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Wondry, I'm Stephen Johnson and this is American Innovations.

It's been a hundred years since John Larson invented his cardio-numos psychograph, later

and more famously known as the LiDetector.

And in that time, the LiDetector has gotten smaller, changed names, and dipped in and

out of popularity, but it never quite gained the respect of the scientific community.

And yet somehow it is persisted in both pop culture and law enforcement.

It's a staple in police dramas and true crime documentaries.

And regardless of its reliability, it's still being used in police questioning across

the country.

Here to tell us more about the LiDetector than and now is Ken Alder, professor of history

at Northwestern University.

He's also the author of the LiDetectors, the history of an American obsession.

Ken Alder, thank you so much for joining us on American Innovations.

That's a pleasure to be here.

So we're really excited to have you on the show because your book was a big inspiration

for the series that our listeners have just heard on the history of the LiDetector.

We get to dive into more of these issues and more of these fascinating characters.

But I think one question that I wanted to start with is just how you got interested in

...