The concept of unconscious mental imagery is a fascinating and counterintuitive idea. For most of us, imagining a sunset or the face of a loved one is a distinctly conscious act. We experience the picture in our mind’s eye. But for people with aphantasia, a condition characterized by the inability to voluntarily form mental images, the mind’s eye is blind. This raises a compelling question: could they be forming mental images without any conscious awareness?
A new paper in the journal Consciousness and Cognition, titled “Aphantasia and the unconscious imagery hypothesis” explores this very possibility. Authors Andy Mckilliam and Manuela Kirberg take a deep dive into the research suggesting that unconscious mental imagery might explain some of the perplexing abilities of people with aphantasia.
The Surprising Evidence for Unconscious Mental Imagery
Historically, mental imagery was considered an exclusively conscious phenomenon. Philosophers and scientists alike defined it by the experience it produces. However, recent studies on aphantasia have challenged this long-held view.
Researchers noticed that people who report having no mental imagery often perform surprisingly well on tasks thought to require it, such as mentally rotating objects. As the paper notes, this is “exactly what we would expect if they are engaging in imagery unconsciously”. If an aphantasic individual is rotating a mental image without being aware of it, their performance would naturally be similar to someone with typical imagery.
Further evidence comes from sophisticated neural decoding studies. Using functional magnetic resonance imaging, or fMRI, scientists have found that imagery-related information is being processed in the visual cortex of aphantasic individuals, even when they report no visual experience at all. In one study, researchers could predict what sound a person with aphantasia was hearing (like a dog barking) just by looking at the activity in their brain’s visual center. This suggests a link between hearing and seeing that might be happening completely under the radar of consciousness.
A Closer Look Reveals a More Complicated Picture
While this evidence seems compelling, Mckilliam and Kirberg argue that we should be cautious before concluding that unconscious mental imagery is real. They methodically dissect the existing studies and suggest that alternative explanations might be more likely.
One major issue is what psychologists call “response bias”. When someone fills out a questionnaire about their mental imagery, they must decide what qualifies as a “picture in the mind”. Some people might have a very strict criterion and report “no image” if what they experience is fleeting or dim, even though there is some conscious experience present. The authors point out that one study found “a full 30% of the participants who scored 16 on the VVIQ – answer ‘no image’ to all 16 questions – also reported ‘brief flashes’ of imagery” when a more carefully worded questionnaire was used. This suggests that some cases of supposed aphantasia might actually be cases of very weak, but still conscious, imagery that gets misreported.
Another problem is that the brain activity seen in neural decoding studies might not qualify as true imagery. The authors highlight a study where the neural patterns associated with imagery in aphantasics were in a “different format” than those from actual perception. The researchers in that study concluded that aphantasics might engage in “imageless imagery,” a process that involves the brain’s sensory areas but doesn’t create a picture-like representation. Mckilliam and Kirberg question whether this concept has been “stretched beyond breaking point,” asking, “If this information is not encoded in a depictive or perceptual format, does it really warrant the label mental imagery?”.
How Can We Find the Truth?
So, how can science solve this puzzle? The authors propose a clear path forward for research on unconscious mental imagery. They argue that instead of relying on just one measurement, researchers need to combine multiple methods.
First, they should use both subjective reports (like questionnaires) and objective physiological markers, such as imagery-based priming effects in binocular rivalry experiments or changes in pupil size. This would help identify individuals who report no imagery but whose bodies react as if they are producing it.
Second, once these candidates are identified, a deeper investigation is needed to rule out response bias. Mckilliam and Kirberg suggest looking for a “cluster of markers of consciousness”. For example, conscious processing is typically required for complex tasks like integrating information from multiple senses or overriding automatic, primed responses. If a person shows physiological signs of imagery but lacks these associated conscious abilities, it would be strong evidence that their imagery is genuinely unconscious.
The debate over unconscious mental imagery is far from over. As Mckilliam and Kirberg conclude, “the existing evidence for unconscious imagery is far from conclusive”. Their work provides a critical perspective and a rigorous framework for future studies, pushing the field of aphantasia research toward a clearer understanding of the hidden complexities of the human mind.