When the mind's eye is blind: What causes aphantasia?

The ability to visualize things such as the faces of our loved ones, objects, landscapes, or even past memories varies greatly among individuals. While most people take this ability for granted, there is a segment of the population that cannot conjure up vivid images on demand. These individuals live with a blank mental canvas that lacks visual imagery, which is a condition known as aphantasia.

One surprising aspect of aphantasia –  especially in cases where it’s congenital and not a result of any brain injury, stroke, or psychiatric illness – is that many individuals remain unaware of this trait for a significant portion of their lives. 

This is because it doesn’t interfere with their day-to-day functioning. In fact, some people with aphantasia have no idea that they deviate from the norm.

On the opposite end of the spectrum, there is a group of individuals known as hyperphantasics. Their minds work like high-resolution canvases, capable of producing mental images as sharp and clear as illustrations in a book.

Aphantasia and visual information 

Paolo Bartolomeo, a renowned neurologist and researcher at the Paris Brain Institute, shared his fascination with these cognitive variations.

“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,” said Bartolomeo.

“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.”

How researchers studied aphantasia 

The origin of aphantasia remains a topic of debate among researchers. Is it a perceptual deficit? Could emotional and psychological factors be at play? Or does it stem from difficulty in accessing sensory information?

To investigate, Bartolomeo teamed up with Jianghao Liu, a doctoral student specializing in Neurophysiology and Functional Neuroimaging at the Paris Brain Institute. 

The experts embarked on a study with 117 volunteers, including 44 aphantasics, 31 hyperphantasics, and 42 individuals with average mental imagery capabilities. 

The research involved a mental imagery and visual perception test termed the “Imagination Perception Battery (BIP).”

“Our test…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,” said Liu.

The scientists exposed participants to a multi-modal test. This required them to visualize concepts based on auditory cues and then match them with appropriate qualifiers. They recorded their speed, accuracy, and self-assessed quality of visualization.

In addition, the team conducted a perception test, presenting stimuli visually, eliminating the need for mental visualization.

Phenomenal consciousness

“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,” said Liu. 

“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.”

“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,” explained Bartolomeo.

“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.”

“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.”

Looking ahead

While the aphantasia study provides intriguing insights, it’s essential to note its limitations. Primarily, the reliance on an online questionnaire for data collection. However, it has paved the way for further exploration into understanding the complexities of visual mental imagery.

Potential future studies could explore the neural mechanics behind these observations. This would shed light on specific visualization deficits experienced by 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,” said Liu.

The research is published in the journal Cortex.

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