On the SGU we recently talked about aphantasia, the condition in which some people have a decreased or entirely absent ability to imagine things. The term was coined recently, in 2015, by neurologist Adam Zeman, who described the condition of “congenital aphantasia,” that he described as being with mental imagery. After we discussed in on the show we received numerous e-mails from people with the condition, many of which were unaware that they were different from most other people. Here is one recent example:

“Your segment on aphantasia really struck a chord with me. At 49, I discovered that I have total multisensory aphantasia and Severely Deficient Autobiographical Memory (SDAM). It’s been a fascinating and eye-opening experience delving into the unique way my brain processes information.

Since making this discovery, I’ve been on a wild ride of self-exploration, and it’s been incredible. I’ve had conversations with artists, musicians, educators, and many others about how my experience differs from theirs, and it has been so enlightening.

I’ve learned to appreciate living in the moment because that’s where I thrive. It’s been a life-changing journey, and I’m incredibly grateful for the impact you’ve had on me.”

Perhaps more interesting than the condition itself, and what I want to talk about today, is that the e-mailer was entirely unaware that most of the rest of humanity have a very different experience of their own existence. This makes sense when you think about it – how would they know? How can you know the subjective experience happening inside one’s brain? We tend to assume that other people’s brains function similar to our own, and therefore their experience must be similar. This is partly a reasonable assumption, and partly projection. We do this psychologically as well. When we speculate about other people’s motivations, we generally are just projecting our own motivations onto them.

Projecting our neurological experience, however, is a little different. What the aphantasia experience demonstrates is a couple of things, beginning with the fact that whatever is normal for you is normal. We don’t know, for example, if we have a deficit because we cannot detect what is missing. We can only really know by sharing other people’s experiences.

For example, let’s consider color vision. Someone who is completely color blind, who sees only in shades of grey, would have no idea that they are not seeing color, or that color exists as a phenomenon, except for the fact that other people speak of the fact that they perceive this thing called color. Even then it may take time as they grow to realize that other people are experiencing something they are not. But if they lived in a world with color-blind people, they would never know what they are missing.

This also relates to the old question – is what I experience as “red” the same thing that you experience as “red”? Is there any way we can know? We can only infer from indirect evidence. It’s likely that people experience colors similarly since we tend to associate the same emotions and feelings to those colors, but of course that could also be learned. However, there is no reason to assume our color experiences are identical. There are likely differences in vibrancy, contrast, shading, and other details. Also there are many people who are partially color blind (like me – I have a deficit in red-green distinction). I would never ever know, however, that my color vision was different than most people were it not for those tests we were forced to take where we try to see the number in the circles.

Similarly, if  you cannot form visual mental representations in your mind, you might assume everyone is that way. Several people with aphantasia have told me that when other people talked about “seeing” things in their mind, they assumed it was a metaphor. They had no idea other people were literally seeing an image in their mind.

Sometimes even the objective lack of a sensory experience might be entirely unknown to the person. For example, people who are born with a decrease in sensation because of a disorder of their nerves do not know this. Whatever sensation they have is normal for them. So they don’t complain of numbness, even though on exam they have a profound decrease in sensation (that’s how we know its congenital and not acquired).

We should, I think, extrapolate from this experience. There are likely countless ways in which our brains differ from each other in how they construct our subjective experience of reality, our abstractions, our emotional worlds, and our sensory perceptions. These are all brain constructs, dependent on the particulars of networks and nodes in the brain, how they connect, and how they function. We cannot get outside of this – this is who and what we are.  This is why neuroscientists have moved toward the concept of “neurodiversity” – understanding the full diversity of how different human brains function. There may be a “typical” brain, in one or more aspects, but there is also lots of diversity. We also should not automatically pathologize this diversity and assume anything not typical is a “disorder” or even worse, a “disease.” Mostly biological diversity is a matter of different tradeoffs.

Even when we recognize that some forms of neurodiversity may quality as a “disorder”, meaning that there are demonstrable objective negative outcomes, sometimes this is very context dependent. They may only have negative outcomes because neurotypicals have designed society to best suit them.  They may be on the short end of the tradeoffs, but that is not an inherent reality, just a societal choice.

Even more fascinating to me is to think about the universal human neurological experience. In other words – what do humans lack, or in what ways is human experience of reality idiosyncratic? Just like those with aphantasia, we likely will never know – not until we encounter other intelligent species who experience reality differently. If we are even able to sufficiently communicate with them, we may find their realities are very different from our own. Until then we may not know what it truly means to be human.