The next morning he began questioning his friends about their experiences and doing some Internet research. To his great surprise, he found that the ability to visualize images is real—except not for him.
His study included control subjects. Most of them showed a moderately good ability to visualize. But there were outliers at both ends of the scale, with more subjects falling at the high end than the low end.
Zeman calls the above-average ability to create vivid images hyperphantasia. The research has raised a number of questions. One is whether aphantasia exists at all. Could people who think they are not making mental images simply be describing their images differently from the way other people do?
After all, surveys elicit subjective descriptions, not objective measures of what is going on in the brain. Zeman admits that answers on the questionnaire are prone to a certain amount of error, but he is convinced that aphantasia actually occurs. For example, some individuals with aphantasia report weakness in autobiographical memory, remembrance of events in their lives.
In addition, many with aphantasia also suffer from prosopagnosia, impaired face recognition. To Zeman, the links to other conditions indicate that there may be several subgroups of aphantasia. Joel Pearson, professor of cognitive neuroscience at the University of New South Wales in Australia, also considers aphantasia to be real.
As part of his work, he studies binocular rivalry, a perceptual phenomenon that occurs when people are shown different images simultaneously to their left and their right eye.
Here subjects do not see a combination of both images but rather only one at a time. Pearson and his team have discovered that a simple trick can influence which image is given priority. Asking volunteers to visualize one of the images before the test increases the probability that that image will come to the fore during the test.
Yet self-diagnosed aphantasics are unaffected, indicating that visualization is impaired. Zeman and others are also exploring how brain functioning differs in those with aphantasia. He and his colleagues recently invited more than people to undergo a brain scan at his laboratory.
They found that when individuals who scored high on the VVIQ were asked to visualize something, only a few brain areas became activated. Researchers have found that these regions light up when processing complex images, such as faces, events and spatial relationships.
In contrast, more and different brain regions lit up in people who reported that they lack the ability to visualize. Those individuals tended to use regions associated with the control of behavior and planning, as was seen in MX. Zeman has not yet studied extensively the other extreme, hyperphantasia. Many people with hyperphantasia have told him, however, that they easily lose themselves in daydreams about the past or the future. In contrast to aphantasia, hyperpahantasia has not yet been found to have links to face recognition or memory.
Zeman initially presumed that visualization was central to the creative process. Yet many of the people with aphantasia who contacted him work successfully in creative professions—as artists, architects and scientists.
Jonas Schlatter, for example, creates Web sites for a start-up that he founded. His business partner thought it a bit odd that he used whiteboard, paper and a pencil in the design process. But Schlatter now understands that this approach is the only way that he can anticipate how the Web pages will eventually look. But while Niel is very relaxed about his inability to picture things, it is a cause of distress for others.
One person who took part in a study into aphantasia said he had started to feel "isolated" and "alone" after discovering that other people could see images in their heads. Being unable to reminisce about his mother years after her death led to him being "extremely distraught". At the other end of the spectrum is children's book illustrator, Lauren Beard, whose work on the Fairytale Hairdresser series will be familiar to many six-year-olds. Her career relies on the vivid images that leap into her mind's eye when she reads text from her author.
When I met her in her box-room studio in Manchester, she was working on a dramatic scene in the next book. The text describes a baby perilously climbing onto a chandelier. Not many people have mental imagery as vibrant as Lauren or as blank as Niel. They are the two extremes of visualisation. Adam Zeman, a professor of cognitive and behavioural neurology, wants to compare the lives and experiences of people with aphantasia and its polar-opposite hyperphantasia. His team, based at the University of Exeter, coined the term aphantasia this year in a study in the journal Cortex.
Prof Zeman tells the BBC: "People who have contacted us say they are really delighted that this has been recognised and has been given a name, because they have been trying to explain to people for years that there is this oddity that they find hard to convey to others.
Look at these shapes for a few seconds. Then close your eyes, and try to imagine how they look. Try to take the mental image of one of them and break the shape into pieces in your mind, or combine it with another shape to make something new. A new study from scientists at Dartmouth College paints a fuller picture of this mental workspace by imaging the brain regions involved with mentally manipulating images, like the shapes above.
0コメント