Humans began to rapidly accumulate technological knowledge 600k years ago

I find it hard to believe that they can't at all imagine what a tree looks like or imagine a face of a friend. I can understand some difficulty in a perfect image, but nothing?

There's a spectrum, but some people see nothing at all. It's known as aphantasia.

The fun thing is that for those of us who cannot it’s as hard to believe others can conjure images. Yes the idea of mental imagery is deeply ingrained in our language but I’d always assumed it was allusion till I learned of aphantasia when I was 30.

One of the more cliche, and not super useful tests, is “imagine a ball on a table, someone pushes the ball and it begins to roll. What color is the ball?” For me that was a revelatory statement because I’d never consider that others might give the ball a color, or size, or texture as the imagine it. I assume not everyone with the ability to visualize does but it seems like many do according to the literature. To me it’s just a statement, a ball is rolling pushed by a nondescript person.

I feel like I kinda have this, and I'd describe it like this:

With actual vision, there's a pipeline of steps: light hits actual cone/rod cells -> optic nerve fires -> brain stage 1 -> brain stage 2 -> brain stage 3... where each of those stages also have various side effects associated with the experience of "seeing"

I can't synthesize "brain stage 1" at all I don't think, I need my optic nerve to send some signals to "see". But I think I might be synthesizing "brain stage 2" when I imagine seeing e.g. a red apple in a pretty similar way to actually seeing it - I can feel "red apple vibes" but there is no image of a red apple my field of view. My brain state certainly contains some data about the color of the imaginary apple and the shape of it, but it's not nearly the same as actually seeing it.

This is all astonishingly hard to explain in a way that communicates accurately between two people though.

I basically only can see in dreams and visions, but rarely remember full images. Basically, everything in my mind is in a compressed symbolic state.

The most notable difference is if you ask me to imagine something, there isn’t any detail in the “image” that I haven’t intentionally placed there. “Imagine the face of a stranger you haven’t met before; what color are their eyes?” Idk, I can add eye color to the image, but I certainly can’t just observe it, because both before and after it’s just the concept, not like a picture I can just look at.

I started training to develop the ability around age 10 or so. As far as I can tell, it wasn't an innate capacity in my case.

It's part of the reason why discussions about consciousness often result in people talking past each other, when they start with the assumption that other humans think just like them.

So for me I definitely visualized a ball on a table, but the color wasn’t resolved, if that makes sense. After hearing the question asked it kind of snaps out of superposition into a red color (but there was definitely a color-choosing step that happened after hearing the question).

Same thing happens if you ask “what surface is the table on” or “what country is this image in”. It’s layers I can add to the mental state, but if they’re not important they’re just not there.

I’d say the closest thing to what I was “seeing” before the color question is something like a wireframe, or maybe the gray color of a Blender model without colors/textures applied. Grey in the sense that you don’t really notice it’s grey, you just understand the grey color means color is absent.

Absolutely same. I wonder how much of it is most people being like this and many of those saying "well yes of course I see the apple" without really thinking about it. If someone actually sees the apple, v.s. imagining what it would be like if they were seeing it, they're hallucinating. Not that it wouldn't be cool to be able to do that on command, I just wonder how many people really can.

Same, at least 90% or so.

I'm terrible at recognising faces - changing a "symbolic" feature like facial hair or glasses will completely throw me - but great at reading maps.

You accurately described my experience.

You described my experience well as well, except my abstract colorless ball was barely even visual. I was quite happy to entertain the idea of a ball on a table with very few concepts activated - roundness for the ball, flatness for the table, gravity holding the ball on the table. Rather like a physics problem.

When forced to dereference a color, it felt like an entire system was booted up. Not only did the ball have color, it also had specular reflections. There was lighting. The table gained an abstract sense of having texture.

What I find particularly fascinating is that my mind also assigned "red". I wonder if that is a coincidence, or a deep reflection of something about how brains work. Supporting evidence: in languages with only three words for color, the three colors are "light", "dark", and "red": https://en.wikipedia.org/wiki/Color_term#Stage_II_(red)

I see nothing at all.

I spent 45 years or so thinking people were talking metaphorically when talking about picturing things, because surely they couldn't actually see things while awake?

I see things when I dream, so I know what it is like, and some years ago I had a single experience during meditation I've never managed to replicate, but otherwise nothing while awake.

I really see it. It's not hallucinating as the imagined image is not in the real world. It's like a different input to the visual processing part of my brain (but both inputs work at once, a bit like looking at a different thing with each eye). I have visual memories (snapshots I can call up) of things I never saw with my eyes (e.g. scenes from novels) that are as strong as any that came from my eyes.

My ball was kind of an indeterminate grey, too, but it was on a granite countertop of a kitchen island in an open concept kitchen/living room. Like one from a Bounty commercial or something.

That’s a really cool description. Makes me think about people complaining of having unwelcome images brought to mind. Which I can relate to through songs. If someone says Baby Shark it’s going to start playing whether I want it to or not.

For me when someone asks “What color is it?” I think to myself “I don’t know you’re the one telling the story you tell me.”

I'll also chime in and say I was able to visualize the generic ball-ness and as soon as the question of color arose, I also immediately picked red despite not being my favorite color or anything. I blame childhood depictions of balls lol

I imagined a small, red, dense foam ball actively being placed by a feminine hand with matching red nails and a fancy bracelet onto a white marble slab with olive green marbling. The slab is a couple inches thick and overhangs the cabinets below it. The point of view, like watching from my own eyes, is looking down at the counter with the ball being placed by the ephemeral hand as if they stood opposite me.

What color was the ball? I didn't have to think; I knew it was red. However, I can't tell you much about the cabinets or the arm or body attached to the hand. Totally unrendered and void.

For me, it is a picture to look at. Like a bust, I had a head and shoulders to look at. The stranger's eyes were deep brown; practically black. They were half asian half white, had black hair, palish white skin, dark eyes, a flat near-smirk. He was wearing a blue collared button up shirt with a mild jeans like texture. The sleeves were rolled up. The buttons were white.

I’m curious, what kind of work do you do? Do your dreams have that kind of detail?

So if I told you to close your eyes and think about your best friend's face....you cannot see ANYTHING?

Software engineer, but I've also been a graphic designer, a photo editor, a fire and casualty insurance agent, a financial services advisor, a construction worker (very basic carpentry, electrical, plumbing, roofing, etc), and high school math teacher, all before being a software developer turned manager turned developer again. And, yeah, dreams have that much detail, but also the extra depth that comes in dreams like knowing intent, emotions, relative history, etc

No. Nothing.

EDIT: This is a great article about Ed Catmull and aphantasia: https://www.bbc.co.uk/news/health-47830256

Can you do it with your eyes open?

Have you tried drawing a real object then the imagined one and seeing which ends up better? I've always thought that this would be a great skill for visual artists.

Interesting and thanks for answering.

If you're on HN, I assume this hasn't impacted you academically?

No reason why it would. My abstract reasoning is far above average, and for that matter my ability to draw used to be far above average, though I'm a few decades out of practice. I "visualize" what things look like and where things are in relationship to each other in the sense that I know where things are with a level of precision well above average - I just can't see it in front of me, though I know where they are and what they look like.

I use the term "visualize" because that is what I thought people meant when they said to visualize or imagine things. I remember the shape of the visual rendition of source code, for example, and that is usually the basis for how I navigate large code bases. And I know what parts of papers I last read 30 years ago look like, but I can't see them.

I think the biggest way it has impacted me is that e.g. when it comes to fiction, I find visual descriptions of things usually bore me unless the language used in itself is particularly compelling because the words themselves are beautiful to me. So I often skip and skim visual descriptions.