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Back in the 1950s, a psychiatrist described a man who complained that his head felt "twice its normal size and as light as a feather." He also occasionally felt like one of his limbs was missing. Around the same time, another middle-aged woman reported to a clinic that she felt that she “got so big that if [she] put out [her] hand [she] could touch the far wall," or that her hands would "drop off and disappear." Curiouser and curiouser.

At least, that's what the doctors thought — which is why these types of symptoms are known as Alice in Wonderland Syndrome. Fortunately, these sorts of symptoms are rare — and seem to be related to easily treatable conditions. Symptoms of Alice in Wonderland syndrome all seem to involve distorted perception, and are most common in kids.

In a 1998 paper, one child reported seeing his TV screen upside down, and that the windows of his house seemed crooked. Another young girl reported seeing ghosts, and people looking distorted. These are all examples of some common visual hallucinations associated with the syndrome, all generally called metamorphopsia, or visual distortions of size, movement, or color.

Like perceiving things as smaller or larger than they actually are. Other types can seem like looking at everything through a telescope — or like looking at everything through the wrong end of a telescope. There are also auditory symptoms, like hearing people's voices become distorted, or hearing unexplained music, voices, or other noises.

But there's a key difference between these hallucinations and ones you'd experience for other reasons, like drug use or schizophrenia. People with Alice in Wonderland syndrome always seem to know they're illusions. They don't get confused about what's real and what's not.

So where do these weird sensations come from? Doctors first identified them as possibly related in the early 1950s. . But according to more recent research, migraine and epilepsy aren't always involved.

A more common explanation is that it's a side effect of having some kind of an infection. In fact, one common infection that's been proposed is the Epstein-Barr virus — more commonly known as mononucleosis, or mono. We're not quite sure how infections could cause hallucinations, but we have some ideas.

One likely explanation is that an infection could change how much oxygenated blood gets to certain regions of the brain involved in processing sensory input. That 1998 study tested this idea with four kids with Alice in Wonderland syndrome. That's a small sample — but remember, it's a pretty rare condition.

And they also checked to be sure these kids didn't have one of the other common explanations for the disorder, like migraine or epilepsy. Three of the four had had a recent upper respiratory infection, and two had the Epstein-Barr virus. And all four kids experienced decreased blood flow somewhere in their brain.

The sides and parts of the brain involved varied. But it was common for it to be somewhere near the visual pathway of the brain, in areas where outside stimulation is known to create hallucinations. The researchers were reluctant to jump to conclusions from such a small sample, but the data seem to fit a scenario in which the infection reduces blood flow and affects visual processing.

But in a pretty amazing case study in 2010, one child experienced symptoms while in an MRI machine. Compared to a matched control participant, the child had more activation in the parietal lobe, and less activation in vision centers, while performing some spatial reasoning tasks. And while it's never a great idea to draw huge conclusions from a study with a sample size of one, it does fit some other things we know about spatial reasoning.

Like, we know the parietal lobe plays a big role in spatial reasoning, and there's a parietal visual pathway that's typically associated with perception of where things are in space. And other studies have linked parietal lobe activation to illusions about the perceived size and shape of your body. For example, you can trick people into thinking their waist is shrinking by having them put their hands on their hips while experimentally vibrating some tendons in their wrists.

In a study in 2005, people who felt that illusion more strongly also had more activation in two parts of their parietal lobe, suggesting they're involved in your sense of how big your body is. But while this evidence points us in the right direction, there's still a lot of dots that need to be connected in explaining exactly how these illusions emerge. In fact, about half of people who experience these Alice-esque symptoms have no clear reason when diagnosed — no migraine, no infection, nothing.

The good news, though? It's also pretty likely for it to just... go away. Although there is one reported case of the syndrome being the result of a rare degenerative brain disorder, many kids just grow out of it — or find treatment for the underlying infection or migraine.

Which relieves the hallucinations. Lewis Carroll himself wrote in his diaries about suffering from migraines. We definitely can't know for sure whether he had these kinds of symptoms.

But given the similarity between the story he wrote and the symptoms others have reported with migraine, some people have speculated that perhaps he experienced these visual illusions himself — and thus Alice's Wonderland was inspired. Thanks for watching this episode of SciShow Psych. If you really want to go down a rabbit hole with us, check out our spin-off podcast, SciShow Tangents.

It's made by some of the same folks who bring you SciShow, but like… slightly more competitive, and with more science poems. Check it out wherever you get your podcasts! [ ♪OUTRO ].