For most of you, the ability to recall what your parents faces look like is no bother at all. But for some, this task is impossible. A few years ago, researchers finally described a condition in which people cannot imagine things in their "mind’s eye", called aphantasia.
Only described recently, a lot of people have grown up assuming that when people asked them to “picture” something in their mind, they were simply talking metaphorically. But now researchers are starting to unravel the truth behind aphantasia, which could affect up to one out of every 50 people (although this is a rough estimate).
One of the hardest things to determine is whether or not aphantasia is actually real, something that a recent study published in the journal Cortex set out to solve. The problem stems from the fact that I cannot know what you can or cannot see, and vice versa. This means that when people are asked to imagine things and then describe that they see, there is no objective measure. We could be seeing the same thing and describing them differently, or seeing different things and describing them the same.
To test this, the researchers devised an experiment known as binocular rivalry. Participants were given a pair of 3D glasses, where one lens shows a green circle with horizontal lines and the other lens shows a red circle with vertical lines. The binocular rivalry illusion induces a state where the images in the two eyes are incongruent and what we see fluctuates between the different images, in this case the colored circles. Before putting these on, however, the participants were asked to imagine one of the colored circles beforehand. If they can indeed picture things in their mind, then the colored circle they were asked to imagine should become the dominant image they see. Those who could not imagine things reported no effect on the binocular rivalry illusion.
So it seems that rather than there being a specific issue with self-reporting, those with aphantasia genuinely cannot imagine things in their mind. The next obvious question then is why this is the case, and if anything could be done to help those who have it.
The most commonly accepted explanation is that when we re-run a memory in our mind's eye, we attempt to reactivate the same patterns of activity as when the memory was formed. It is thought that somehow these neurological pathways are disrupted, or that the brain simply cannot reactivate these pathways in the same way.
If researchers are able to figure out if this is indeed the case, then it could be conceivable for a treatment to be developed that could help people imagine things. On the flip side, it could also be used to treat those with over-stimulated activity patterns, which some think might play a role in addiction, as well as some forms of post-traumatic stress disorder.