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A rare condition that causes people to be unable to picture images in their minds may have more far-reaching effects on the mind than we previously knew, scientists report.
Aphantasia, sometimes referred to as “mental blindness,” has been known since the 19th century, but has only received significant scientific attention in recent years.
These studies tell us more about how aphantasia manifests itself in humans, while also revealing new insights into the importance of mental imagery as part of other brain functions such as memory.
In 2020, a team of researchers led by cognitive neuroscientist Alexei Dawes from the University of New South Wales (UNSW) in Australia found that people with aphantasia showed a reduced ability to recall the past and imagine the future, additionally cause them to remember fewer dreams (and often with fewer details).
Now, in a new study, some of the same scientists have uncovered new evidence of the effects of aphantasia on our memory and ideas about the future.
“Episode memory and future prediction are functionally similar,” says Dawes, now a researcher at the RIKEN Center for Brain Science in Japan. explained in a Twitter thread about the new knowledge.
“Both are everyday cognitive processes that involve the reconstructive simulation of events and scenes, typically accompanied by anecdotally vivid online sensory replays (or ‘preplay’) in the form of visual imagery.”
While these internal visual images are something our minds constantly conjure up, we still don’t know much about how these images affect our ability to actually recall episodes from the past.
To investigate this, Dawes and other researchers conducted an experiment with about 60 participants, half of whom suffered from aphantasia while the other half were people without the condition, who acted as a control group.
In the experiment, participants completed an adapted version of the autobiographical interview, a test designed to assess components of autobiographical memory in adults.
In the version conducted here, participants were asked to recall six life events (real memories) and imagine six hypothetical future events based on word cues, providing detailed written descriptions of each.
The results showed that aphantastic participants generated significantly less episodic detail than participants in the control group for both past and future events.
These included significantly weaker visual imagery, object imagery, and scene imagery, the researchers noted, but found that people with aphantasia performed similarly to controls on spatial imagery ability.
“Most importantly, the current study provides the first robust behavioral evidence that the absence of visual imagery is associated with a significantly reduced ability to simulate the past and construct the future,” the researchers write.
“Aphantastic participants generated significantly less internal detail than controls, regardless of temporal direction, indicating that their event descriptions were less episodic rich and specific than participants with visual images.”
Although we can’t yet estimate the magnitude of the impact, the researchers say the ability to create visual images is important in the mental construction of events, whether it’s reconstructing real-life memories or imagining scenarios that did not take place.
The fact that both past memories and imaginary future expectations are equally affected could support the so-called constructive episodic simulation hypothesis, which posits that future exploration is a cognitive process that stitches fragments of past memories together to paint a picture of possible future events.
“According to this report, internal ‘re-experiencing’ and ‘pre-experiencing’ events should both involve the recombination of stored perceptual, spatio-temporal and conceptual information and therefore rely on similar cognitive processes – including mental images,” the researchers explain.
Of course, this does not mean that people with aphantasia cannot do this remember past events or imagine future ones, the researchers note.
But it appears that their ability to construct or reconstruct these internal scenes is reduced compared to people without the condition, whose ability to rely on a larger set of mental visual images gives them an advantage in unlocking memories seem to provide.
There’s still so much we don’t know about how this state works, but studies like this help fill in the details — not just about aphantasia, but about how memory and visual imagery intersect (or Not). our heads.
“The interactions between visual imagery, the construction of episodic events, and autobiographical memory are likely to be complex, and are further complicated by the myriad individual differences that moderate each of these cognitive processes,” the researchers write.
“However, Aphantasia provides a unique model to begin exploring these interactions and to build a broader taxonomy of cognitive simulation in the human brain.”
The results are reported in Understanding.
