He wrote it along with Humberto Maturana, Warren McCulloch and Walter Pitts, and in the paper they gave special thanks and mention to Oliver Selfridge at MIT.

[9] After the war, he continued practicing neurology and researching nervous systems, partly at Boston City Hospital, and then at MIT with Walter Pitts and Warren McCulloch under Norbert Wiener.

MIT Technology Review described this experiment: "The assumption has always been that the eye mainly senses light, whose local distribution is transmitted to the brain in a kind of copy by a mosaic of impulses," he wrote.

They even identified what they called "bug detectors", or cells in a frog's retina that are predisposed to respond when small, dark objects enter the visual field, stop, and then move intermittently.

"The eye speaks to the brain in a language already highly organized and interpreted, instead of transmitting some more or less accurate copy of the distribution of light on the receptors," he concluded.

"[citation needed] Lettvin was an outspoken critic of pseudo-scientific practices relied upon by many of the social sciences, as well as the potential threat posed by Artificial Intelligence.

Lettvin continued to research the properties of nervous systems throughout his life, culminating in his study of ion dynamics in axon cytoskeleton.

[2][16][17] Lettvin was a regular invitee at the Ig Nobel Prize ceremony as "the world's smartest man," and debated extemporaneously against groups of people on their own subjects of expertise.