In the 1890s, when technologies like telephones and automobiles and lightbulbs were still strange and wonderful and new, inventors promised another remarkable device would soon be ubiquitous: the mind-reading machine. 

Inspired by the phonoautograph—a new device that showed what sound waves looked like on paper—the scientist Julius Emmner invented a machine that he said could record thoughts. It was simple, really. If invisible sound vibrated in a ways that could be measured, Emmner figured, why wouldn't unseen thoughts do the same?

"Sound is addressed to the ear," he told The Times of Washington, D.C., in August 1895, "yet it may be made visible, a proof of which fact is found in the phono-autograph, in which the vibrations of sound are made distinctly visible." Reporters took him at his word. From that same article: "Mr. Emmner is carefully guarding his secret, but he speaks so enthusiastically of his success that he must have obtained the most satisfactory results so far from his investigations."



Reports of thought-reading machines were common in those days. "Secrets will cease to be hidden in the day when the perfected psychometer comes into general use," the Seattle Star declared in a 1908 article about Columbia University professor Frederick Peterson's lie-detector-esque "mind-reading machine."

Seattle Star, 1908 (Library of Congress)

Peterson's device was made out of a mirror, a lamp, a horizontal glass scale, and a galvanometer—a tool to measure electric current. It was designed to shine light on a person whose hands would be resting on copper-plate electrodes. That person would be instructed to say any words that came to mind, and if the beam of light shining on him moved more than 6 to 8 centimeters in response, Peterson interpreted it as a "complex" emotion.

Okaaay. So it doesn't exactly sound like the "instrument of precision" the Starclaimed it to be, but coverage of Peterson's apparatus clearly highlights the era's cultural obsession with mind-reading as the next big thing in technology. By 1910, a British psychologist claimed that thoughts vibrated enough to be discernible to those "constantly attuned" to the phenomenon. Others in academia focused on the visible form a thought might take—what colors could thoughts be? And what would those different colors mean? In 1938, The New York Times called the idea of a thought-reading machine "delightfully plausible." 

Omaha Daily Bee, 1901 (Library of Congress)

Decades of neuroscience research later, most of these mind-reading designs sound absurd. But you can't blame people for wanting to believe. The best real-life technology begins with marvelous, outlandish ideas. Consider the technological advances that adults of the late 1800s had just lived through: Humans could now be captured on camera (1838), there were devices that could snatch sound from the air and record it (1860), people in different houses could have real-time voice conversations by talking into machines (1876), and electric lights had just been installed in the White House (1891)! 

The concept of recorded sound was still so new in the 1890s that it seemed reasonable—or at least the tiniest bit possible—to think recorded sound might be a precursor to recorded thought. Sounds had always been something you heard once, while they happened, and never again. 

And if you haven't tried recording someone's thoughts, how do you know you can't do it? In the same way that if you haven't seen the surface of the moon, why shouldn't you be open to the idea of moon elephants roaming on it? When a new telescope was debuted in Paris in 1899, The Times (of Richmond, Virginia) called it the "telescope by which animals as large as an elephant can be plainly seen upon the moon" and promised it would "show us the large animals upon the moon and their movements." 

The Times (Richmond, Va.), 1899 (Library of Congress)

It was an age of mind-reading machines, and moon elephants, and horse-powered hippocycles (to be fair, the hippocycle inventor called his design, below, more theoretical than practical): 

San Francisco Call, 1896 (Library of Congress)

And although video calls didn't become a reality in 1912, as the Chicago Day Book predicted ...

Day Book, 1912 (Library of Congress)

... they did become a reality. Timeless ideas, it turns out, often just have to wait for technology to catch up with them. Other ideas eventually recede.



The promise of a mind-reading machine was, in its day, a sort of shorthand for what might be technologically possible. And a willingness to believe—or at least to explore—such an idea reflects the kind of optimism that's still essential to invention. The culture of what could be is part of how we organize all kinds of ideas about the world. It's in that same spirit today that we talk about the promises of stem cell research and gene therapies, advances in cryogenics and artificial intelligence, the search for life on other planets, etc.

And yet there's an irresistible construct about technology of the past, a way of thinking that obsesses over what we got wrong. It's that part of you that says: Of course we don't have mind-reading devices. And this is kind of funny because we tend to swing to the opposite extreme when considering possibilities for the future. A machine that does simple math isn't just a useful new tool but something that "will supplant brains."

Day Book, 1915 (Library of Congress)

But that "mechanical brain" didn't supplant the human brain any more than Julius Emmner's secret machine read minds. World-changing technology has never been about devices or machines, but rather people's interactions with them. Only by pushing the boundaries of what's possible can we discover what's real. 

Scientists, by the way, are still designing mind-reading experiments.