Neuroscientist reveals how the brain functions without a mind’s eye

PsyPost’s PodWatch highlights interesting clips from recent podcasts related to psychology and neuroscience.

On Wednesday, January 28, the Speaking of Psychology podcast, hosted by Kim Mills, released an episode featuring Joel Pearson. Pearson is a cognitive neuroscientist and professor at the University of New South Wales, where he directs the Future Minds Lab. The episode investigates the science of aphantasia, a condition characterized by a blind “mind’s eye,” and examines how researchers verify this invisible experience.

At roughly the 3-minute mark, Pearson defines aphantasia as the inability to voluntarily create mental images. He notes that while the concept was first described by Francis Galton in the 1880s, it was only formally named in 2015. This new label sparked a wave of public interest, leading many people to realize for the first time that their lack of internal imagery was not the norm.

Pearson estimates that this condition affects at least 4 to 5 percent of the population, though the real number could be higher. He explains that standard questionnaires often fail because people with aphantasia may believe that “visualizing” is merely a figure of speech. These individuals are often surprised to discover that others literally see pictures in their minds.

To gather more accurate data, scientists have developed objective tests that do not rely on personal opinions. One method involves binocular rivalry, a visual illusion where a different image is shown to each eye at the same time. Pearson found that if a person imagines one of the patterns beforehand, their brain is usually prepared to see that specific image, but this effect does not happen for those with aphantasia.

Researchers also use physiological tracking, such as measuring pupil dilation. When a typical visualizer imagines a bright light, their pupils constrict to protect the eye, just as they would in actual sunlight. Pearson points out that people with aphantasia do not exhibit this reflex, which provides physical evidence that no image is being generated.

The conversation also addresses physical differences in the brain. Pearson explains that strong visualizers often have a larger visual cortex and lower levels of “noise,” or baseline neural activity, in that area. He suggests that a quieter background state in the brain might be necessary for clear mental pictures to form.

Finally, Pearson discusses how a lack of imagery can influence emotional regulation. He describes mental visualization as an amplifier that makes memories and stories feel more intense. Because of this, people with aphantasia may feel less fear when reading scary novels and could be less prone to the vivid flashbacks associated with post-traumatic stress disorder.

You can listen to the full interview here.