[donw]

It works the other way around: polygraphs need to show that they work in replicated, controlled experiments.

That hasn't happened[1].

Lying is a complex behavior. Like, really complex. Even with all of modern technology, we've only just started to detect far more gross brain functions: pre-speech motor patterns, fear responses, etc.

It goes without saying that an MRI is at least slightly more complicated than something you could knock together in an afternoon after a shopping trip to Radio Shack in 1963.

Polygraphs are a $2 billion industry, and Upton Sinclair said it best: "It is difficult to get a man to understand something, when his salary depends on his not understanding it."

[1] https://en.wikipedia.org/wiki/Polygraph