Summary: Visualization abilities range from hyperphantasia, where individuals can create vivid mental images, to aphantasia, where people experience a complete absence of visual imagery.
A study assessed the link between perception and mental imagery in individuals across this spectrum. While aphantasics accurately perceive elements of reality and show no deficits in memory or language processing, they may have a slight defect in phenomenal consciousness, preventing the transformation of visual information into visual mental images.
This understanding paves the way for potential treatments for conditions like PTSD, characterized by intrusive mental imagery.
Aphantasics can describe objects and people they know but cannot mentally visualize them.
People with aphantasia can perceive elements of reality and remember what they’ve seen, suggesting they might rely on non-visual cognitive strategies.
The Paris Brain Institute’s study is a stepping stone to understanding and potentially treating visualization deficits and conditions like PTSD.
Source: Paris Brain Institute
The ability to visualize faces, objects, landscapes, or even scenes from the past exists on a spectrum. While some can picture the layout of a city in minute detail and mentally walk through it, street by street, others have a perfectly blank internal cinema. In this case, we speak of aphantasia—the inability to voluntarily produce the visual mental image corresponding to an idea.
People whose aphantasia is congenital—i.e., not due to a stroke, brain injury, or psychiatric illness—become aware of their peculiarity reasonably late in life. Indeed, this small deficit in visualization does not cause any handicap, and they have no reason to suspect they are atypical. Nor do they realize that at the other end of the spectrum are hyperphantasic individuals who can produce mental images as precise as illustrations in a book.
“Talking to these people is fascinating. We tend to think that access to visual perception, conceptualization, and memory is the same for everyone. Nothing could be further from the truth,” Paolo Bartolomeo, neurologist and researcher at Paris Brain Institute, says.
“Aphantasics cannot mentally picture what their parents, friends, or partner look like when they are away. But they can still describe the physical characteristics of their loved ones: this visual information has been stored, in one way or another”.
Visual mental imagery in question
There is currently a lively debate about the origin of aphantasia. Is it linked to a perceptual deficit? Emotional and psychological factors? A slight difficulty in accessing one’s sensations?
To answer this question, Paolo Bartolomeo and Jianghao Liu, a doctoral student in the “Neurophysiology and Functional Neuroimaging” team at Paris Brain Institute, recruited 117 volunteers—including 44 aphantasics, 31 hyperphantasics and 42 people with typical mental imagery—and gave them a mental imagery and visual perception test.
“Our test, called the Imagination Perception Battery (BIP), is designed to assess the link between perception and mental imagery through the different visual qualities that enable a scene to be described—such as shape, color, position in space, presence of words or faces”, Jianghao Liu explains.
Participants were asked to look at a blank screen. At the same time, an off-screen voice announced a visual quality (such as ‘shape’), followed by two words corresponding to concepts they had to materialize in their minds as accurately as possible (‘beaver’ and ‘fox’ for example). The voice also gave them a qualifier (such as ‘long’); then, the participants were asked to decide which of the beaver or fox best matched the epithet ‘long’.
The speed and relevance of responses were recorded, and the respondents were asked to assess the quality of the mental image they had—or had not—managed to produce from the description.
Finally, they had to take a perception test in which the stimuli were presented in a visual format: the long fox appeared in the form of an image accompanied by its audio description without the participants having to picture it.
When imagination takes its time
“Our results indicate that the performance of people with aphantasia is equivalent to other groups in terms of perception and the ability to associate a concept with its representation,” Liu comments.
“With one exception! Aphantasics are, on average, slower than hyperphantasics and typical imagers when it comes to processing visual information, particularly shapes and colors. They also have little confidence in the accuracy of their answers”.
Previous studies have shown that aphantasics are just as quick as other people to answer questions that require manipulating abstract concepts. Therefore, only the processing of visual information is delayed for them. How can this phenomenon be explained?
“Participants in the aphantasic group perceive elements of reality accurately and show no deficits in memory and language processing. We believe that they present a slight defect of what we call phenomenal consciousness.
“This means that they have access to information about shapes, colors, and spatial relationships—but that this visual information does not translate into a visual mental image in conscious experience”, Bartolomeo says.
“This peculiarity is probably compensated by other cognitive strategies, such as mental lists of visual characteristics, which allow aphantasics to remember everything they have seen.”
The future of perception
These preliminary results are limited by the data collection method, which consisted of an online questionnaire. However, they put us on a promising track to understand how visual mental imagery works. Future studies could reveal the neural mechanisms underlying these observations and, ultimately, help us to understand the visualization deficits specific to stroke patients.
“We also hope to develop interventional tools for certain psychiatric illnesses, such as post-traumatic stress disorder (PTSD), which is characterized by the eruption of images from traumatic memories. If we could rid patients of these intrusive mental images, it would greatly promote their recovery”, Liu concludes.
About this aphantasia and visual neuroscience research news
Probing the unimaginable: The impact of aphantasia on distinct domains of visual mental imagery and visual perception
Different individuals experience varying degrees of vividness in their visual mental images. The distribution of these variations across different imagery domains, such as object shape, color, written words, faces, and spatial relationships, remains unknown.
To address this issue, we conducted a study with 117 healthy participants who reported different levels of imagery vividness. Of these participants, 44 reported experiencing absent or nearly absent visual imagery, a condition known as “aphantasia”.
These individuals were compared to those with typical (N = 42) or unusually vivid (N = 31) imagery ability.
We used an online version of the French-language Battérie Imagination-Perception (eBIP), which consists of tasks tapping each of the above-mentioned domains, both in visual imagery and in visual perception. We recorded the accuracy and response times (RTs) of participants’ responses.
Aphantasic participants reached similar levels of accuracy on all tasks compared to the other groups (Bayesian repeated measures ANOVA, BF = .02). However, their RTs were slower in both imagery and perceptual tasks (BF = 266), and they had lower confidence in their responses on perceptual tasks (BF = 7.78e5).
A Bayesian regression analysis revealed that there was an inverse correlation between subjective vividness and RTs for the entire participant group: higher levels of vividness were associated with faster RTs.
The pattern was similar in all the explored domains. The findings suggest that individuals with congenital aphantasia experience a slowing in processing visual information in both imagery and perception, but the precision of their processing remains unaffected.
The observed performance pattern lends support to the hypotheses that congenital aphantasia is primarily a deficit of phenomenal consciousness, or that it employs alternative strategies other than visualization to access preserved visual information.