Reeder had tested children’s imagery and believed that most children were hyperphantasic. They had not yet undergone the synaptic pruning that took place in adolescence, so there were incalculably more neuronal connections linking different parts of their brain, giving rise to fertile imagery. Then, as they grew older, the weaker connections were pruned away. Because the synapses that were pruned tended to be the ones that were used less, Reeder thought it was possible that the children who grew up to be hyperphantasic adults were those who kept on wanting to conjure up visual fantasy worlds, even as they grew older. Conversely, perhaps children who grew up to become typical imagers daydreamed less and less, becoming more interested in the real people and things around them. Maybe some children who loved to daydream were scolded, in school or at home, to pay attention, and maybe these children disciplined themselves to focus on the here and now and lost the ability to travel to the imaginary worlds they’d known when they were young.

Cartoon by Adam Douglas Thompson

Clare had not been discouraged from daydreaming as a child, and she had preferred it to the other common form of imaginative dissociation, reading. Daydreaming was more pleasurable for her because she had struggled to learn to read, and even once she knew how she’d found it slow going. When she received a diagnosis of dyslexia, as an adult, the tester told her that, rather than processing individual letters or sounds, she was memorizing pictures of whole words, which made it hard to recognize words in different fonts. Her visual sense was so overweening that reading was strenuous, because she was easily distracted by the squiggles and lines of the text.

Naturally, aphantasics usually had a very different experience of reading. Like most people, as they became absorbed, they stopped noticing the visual qualities of the words on the page, and, because their eyes were fully employed in reading, they also stopped noticing the visual world around them. But, because the words prompted no mental images, it was almost as if reading bypassed the visual world altogether and tunnelled directly into their minds.

Aphantasics might skip over descriptive passages in books—since description aroused no images in their minds, they found it dull—or, because of such passages, avoid fiction altogether. Some aphantasics found the movie versions of novels more compelling, since these supplied the pictures that they were unable to imagine. Of course, for people who did have imagery, seeing a book character in a movie was often unsettling—because they already had a sharp mental image of the character which didn’t look like the actor, or because their image was vague but just particular enough that the actor looked wrong, or because their image was barely there at all and the physical solidity of the actor conflicted with that amorphousness.

Presumably, novelists who invented characters also had a variety of responses to seeing them instantiated in solid form. Jane Austen wrote a letter to her sister in 1813 in which she described going to an exhibition of paintings in London and searching for portraits that looked like Elizabeth Bennet and Jane Bingley, two main characters from “Pride and Prejudice.” To her delight, she’d seen “a small portrait of Mrs Bingley, excessively like her . . . exactly herself, size, shaped face, features & sweetness; there never was a greater likeness. She is dressed in a white gown, with green ornaments, which convinces me of what I had always supposed, that green was a favourite color with her.” Austen did not see Elizabeth at the exhibition but hoped, she told her sister, to find a painting of her somewhere in the future. “I dare say Mrs D.”—she wrote, Darcy being Elizabeth’s married name—“will be in Yellow.”

One of the twenty or so congenital aphantasics who contacted Adam Zeman after his original 2010 paper was a Canadian man in his twenties, Tom Ebeyer. Ebeyer volunteered to participate in Zeman’s studies, and, after Zeman published his 2015 Cortex paper on congenital aphantasia, Ebeyer was one of the participants quoted in the Times article about it. After that, hundreds of aphantasics reached out to him on Facebook and LinkedIn. They asked him questions he didn’t know the answers to: Does this mean I have a disability? Is there a cure?

Many of Ebeyer’s correspondents felt shocked and isolated, as he had; he decided that what was needed was a online forum where aphantasics could go for information and community. He set up a website, the Aphantasia Network. He didn’t want it to be a sad place where people commiserated with one another, however. There were good things about aphantasia, he believed, and he began to write uplifting posts pointing them out. In one, he argued that aphantasia was an advantage in abstract thinking. When prompted by the word “horse,” a person with imagery would likely picture a particular horse—one they’d seen in life, perhaps, or in a painting. An aphantasic, on the other hand, focussed on the concept of a horse—on the abstract essence of horseness. Ebeyer published posts about famous people who had realized that they were aphantasic: Glen Keane, one of the leading Disney animators on “The Little Mermaid” and “Beauty and the Beast”; John Green, the author of “The Fault in Our Stars,” whose books had sold more than fifty million copies; J. Craig Venter, the biologist who led the first team to sequence the human genome; Blake Ross, who co-created the Mozilla-Firefox web browser when he was nineteen.