In 2005, the British neurologist saw a patient who said that a minor surgical procedure had taken away his ability to conjure images. Over the 16 years since that first patient, Dr. Zeman and his colleagues have heard from more than 12,000 people who say they don’t have any such mental camera.
The scientists estimate that tens of millions of people share the condition, which they’ve named aphantasia, and millions more experience extraordinarily strong mental imagery, called hyperphan-tasia.In their latest research, Dr. Zeman and his colleagues are gathering clues about how these two conditions arise through changes in the wiring of the brain that join the visual centers to other regions.
And they’re beginning to explore how some of that circuitry may conjure other senses, such as sound, in the mind. Eventually, that research might even make it possible to strengthen the mind’s eye — or ear — with magnetic pulses. “This is not a disorder as far as I can see,” said Dr. Zeman, a cognitive scientist at the University of Exeter in Britain. “It’s an intriguing variation in human experience.
” The patient who first made Dr. Zeman aware of aphantasia was a retired building surveyor who lost his mind’s eye after minor heart surgery. To protect the patient’s privacy, Dr. Zeman refers to him as M.X.When M.X. thought of people or objects, he did not see them. And yet his visual memories were intact. M.X. could answer factual questions such as whether former Prime Minister Tony Blair has light-coloured eyes.
(He does.) M.X. could even solve problems that required mentally rotating shapes, even though he could not see them. In a 2015 report on those findings, Dr. Zeman and his colleagues proposed that those readers all shared the same condition, which the researchers called aphantasia. To better understand aphantasia, Dr. Zeman and his colleagues invited their correspondents to fill out questionnaires.
One described the condition as feeling the shape of an apple in the dark. Another said it was “thinking only in radio.” The vast majority of people who reported a lack of a mind’s eye had no memory of ever having had one, suggesting that they had been born without it. Yet, like M.X., they had little trouble recalling things they had seen. When asked whether grass or pine tree needles are a darker shade of green, for example, they correctly answered that the needles are. On the other hand, people with aphantasia don’t do as well as others at remembering details of their own lives.
It’s possible that re-calling our own experiences — known as episodic memory — depends more on the mind’s eye than does remembering facts about the world. To their surprise, Dr. Zeman and his colleagues were also contacted by people who seemed to be the opposite of M.X.: They had intensely strong visions, a condition the scientists named hyperphantasia.The strength of the mind’s eye may exert a subtle influence over the course of people’s lives. Dr. Zeman’s questionnaires revealed that people with aphantasia were more likely than average to have a job that involved science or math. The genome pioneer Craig Venter even asserted that aphantasia had helped him as a scientist by eliminating distractions.