Double vision (of the imagination)?
February 25, 2019 5:41 PM   Subscribe

I was walking around, listening to fun beat, and I realized just how strange it was that I could both see the street in front of me and "see" an imagined dance routine at the same time. Yet everyone does this all the time in various ways (e.g reliving memories, envisioning a painting while painting it). What is this phenomenon? How does it work? How does it not contradict what we know about vision?
posted by facehugger to Science & Nature (9 answers total) 4 users marked this as a favorite
Take a read at 'Thinking in pictures' by Temple Grandin. I believe this is called Visual-spatial memory/intelligence. Are you on the spectrum by chance?
posted by OnefortheLast at 6:23 PM on February 25, 2019

Mental imagery is the usual term for this in vision science and visual perception research. I used to work in a lab with a then-postdoc who was interested in studying it.
posted by Making You Bored For Science at 6:27 PM on February 25, 2019

The usual term, if I'm not misinterpreting you, is mental image. That Wikipedia article is very thorough on the neurology, psychology, and even philosophy of the topic.

The lack of the ability is called aphantasia. Neither article goes into this, but my understanding is that for a long time there was a lively debate in philosophy over whether mental images (and other sensation like mental "audio") were a real phenomenon, or people were just using colorful, exaggerated language. In fact, in all likelihood the deniers were just people with aphantasia who refused to accept that others had different perceptions.

I don't know if there's an adequate consensus explanation for how mental imagery is possible, because that could amount to an explanation of one of the single thorniest issues in philosophy today, the mind-body problem.
posted by InTheYear2017 at 6:28 PM on February 25, 2019 [3 favorites]

everyone does this all the time in various ways

Not everyone. I'm one of those aphantasics mentioned above. That said, I have a persistent internal music radio station that's almost impossible to shut down, and I do have quite adequate spatial planning skills; they feel like they're based on imaginary proprioception rather than imaginary vision, but they work quite well.

Quite a lot of brain activity is devoted to modelling the world that brain owners find themselves embedded in, and using that modelling to predict probable futures. I would expect human beings with no perceptual overlap between world-models built from present-moment-derived sensory input and those built internally by memory and imagination to be quite rare.
posted by flabdablet at 6:46 PM on February 25, 2019 [2 favorites]

What is the thing that you think we know about vision that this would contradict?
posted by Lady Li at 6:47 PM on February 25, 2019 [2 favorites]

Aphantasia on the blue.
posted by Johnny Wallflower at 6:56 PM on February 25, 2019

As seeing is several levels up from what is received at the retina, then sight is 'simply' another mental process; much like we can follow more than one conversation simultaneously, likewise we can run a kind of personal head-up-display.
posted by unearthed at 7:10 PM on February 25, 2019 [1 favorite]

To be precise, unless we're talking about hallucinations, it's like the image/video running "offscreen" (without being sent to the computer's video card), rather than superimposed on the same screen.
posted by InTheYear2017 at 12:27 PM on February 26, 2019

What is the thing that you think we know about vision that this would contradict?

This is the question; really it sounds like you might be interested in learning more about vision, which luckily is one of the more studied physical processes.

Unless you're literally hallucinating, visualization is happening at a different remove from the physical phenomenon of photons hitting your eyes and being interpreted by your brain. Blind people, for instance, often have quite vivid mental imagery.

Visualization and vision are distinct phenomena - the Wikipedia article on "Mental Image" has some interesting tidbits. You might also look at information about visuospatial working memory (VSWM) if you're interested in studies about this.
posted by aspersioncast at 12:49 PM on February 27, 2019

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