The evocative blobs and curves of the Rorschach inkblots are ubiquitous. By now, nearly a century after a Swiss psychiatrist developed them—as a neutral panel of images designed to elicit revealing responses in patients—they’ve transcended the realm of diagnostics and become stitched into history and popular culture. The series of cards was used to test Nazi war criminals at Nuremberg prison; animated inkblots morph into one another in the video for Gnarls Barkley’s hit song, “Crazy”; and President Obama declared during the 2008 election that he, himself, was a Rorschach test. The 10 cards, some in black and white, some in color, have been administered to millions of people. They’ve also been portrayed in films, printed on coasters, imitated, decried as pseudoscience, and defended as a valuable window into the psyche.

What are they? Not inkblots, exactly. In fact, the Rorschach images are a series of paintings, carefully crafted to be evocative without looking like they were created for any purpose. Whatever their reputation among psychologists, their enduring appeal even after decades of use and overexposure speaks to their success as an unusual artistic achievement: What they look like depends on who is looking at them. An exhibit on display through June 30 at Harvard’s Collection of Historical Scientific Instruments, “X-rays of the Soul: Rorschach and the Projective Test,” explores the images and the variety of uses and meanings society has found in them since they were published in 1921.

The Rorschach inkblots have their roots in a European parlor game called Klexographie, in which people would create inkblots and imagine what they represented. Hermann Rorschach enjoyed the game so much that he was nicknamed “Klex.” But the idea of using an inkblot to diagnose pathology came when Rorschach, a psychiatrist and artist, realized such images, and the associations they created, might be used to probe the mind in a systematic way. He created a set of 10, tested them extensively in patients and nonpatients, and published a book describing his results and how to use the inkblots.

What drew Harvard University science historian Peter Galison to study these “X-rays of the soul” was that very transformation, from a creative diversion to a technology meant to read out a person’s inner life. To him, that shift was revealing, not because it bared the pathology of the mind of whoever was looking at it, but because the inkblots themselves revealed a shift in the beliefs in the society that adopted them. What the Rorschach test really marked was the spread of the idea of the unconscious—an idea about how the mind works that has proved as timeless as the images themselves. Galison led Ideas through the gallery on a recent visit.

IDEAS:What did the Rorschach test build on?

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A psychologist discusses a patient's Rorschach test circa 1955.

GALISON: People have been interested in chance forms—clouds, fire embers, patterns that they thought of as training the imagination. Leonardo da Vinci said you should study the cracks in walls and clouds and see what you can see there. Learning to do that, he said, is a way of training the imagination. All the way up through the 19th century there was a concept of the self as being made of faculties—there were these pieces of the self, these organs of the self....By the end of the 19th century, this faculty picture of the self that’s composed of these different bits had been organized into something that you could actually test....There were tests for memory and tests for what you could gather at a glance and tests for the imagination. And the test of the imagination was looking at a random image and seeing all the things you can see.

IDEAS:What did Rorschach think he was testing?

GALISON: Rorschach didn’t think of the tests as being at all about the imagination....He thought he was testing perception and how we grasp the world, what did we pick out. Two people look at the same scene, but we pick out different things....He thought that, in a way, our unconscious selves made us pick out certain things that were very revealing of who we were.

IDEAS: When Rorschach was designing this test, did he see it as a window into pathology?

GALISON: Yes. His original book was called “Psychodiagnostics,” and he experimented for a long time on the cards....He would make these inkblots, and vary them in all different ways....One of the things people often don’t know is that the final cards aren’t inkblots at all. He painted them. He used inkblots to generate the forms and to experiment on his patients, to see how they responded, but then he wanted the cards to be as evocative as possible.

IDEAS:Why are images seen as the way of accessing the self?

GALISON: Rorschach did experiment with having people draw, but I think this was considered to be more neutral. It didn’t presuppose any particular mastery of language.

IDEAS: But why not something else, like music?

GALISON: There was an attempt. B.F. Skinner, the great behaviorist, actually developed an audio Rorschach where you would hear random sounds and then say what word you heard.

IDEAS: How did you get interested in studying this?

GALISON:What I’m interested in is the larger study of technologies of the self. I want to know what you have to believe about the self for certain technologies to even come into existence. And then, once the technology exists and becomes very widespread, how does it teach us to think of ourselves a certain way. So in the case of the Rorschach test, the condition without which you can’t have Rorschach’s test is the unconscious. Without an unconscious, none of what Rorschach was doing makes any sense at all. It doesn’t mean you have to subscribe to the detailed psychodynamics of Freud, but it means you have to have some broad idea that there are unconscious predilections for us, picking out certain bits of reality over others.

IDEAS: Do people analyze Rorschach inkblots as art?

GALISON: What’s funny is as soon as you start to talk about the cards, you are also in the mix. You’re saying something about yourself. Which I think is actually very funny. [Andy] Warhol, for instance, said, “I really should get someone else to take these tests for me. They’d see much more interesting things.”