Tuesday, January 15, 2008

Left v. Right

We've all probably heard the concept that different people may experience color differently. Maybe what I see as yellow looks, in my mind, like what the color blue looks like in your mind. There's no real way to answer that question definitively using modern technology and our limited understanding of how the brain works, but in theory with sufficiently advanced technology and a sufficiently advanced understanding of the brain, one could answer that question. Of course, there would be no 'right' or 'wrong' way to perceive colors, but one could at least agree that two people either see things the same, or differently. That said, I've heard somewhere (it could have been through my dad, who as a lawyer, is not an authority on the matter) that we all probably see colors the same way.

The other day I was thinking along similar lines about the whole left/right distinction. The decision of which goes where is arbitrary. If everything in your head were a mirror image of what things were like in reality (we'll come to reality later), then you wouldn't have any problems getting around in the world. You would have learned to read 'backwards', drive on the 'other' side of the road, etc. However, everything would be flipped, so everything would still agree internally. Still, just like the color example we're more familiar with, it's possible that what 'left' feels like in your mind may be what 'right' feels like in my mind.

Now, if two people really do disagree in their minds of where 'left' goes and where 'right' goes, and we somehow figure out a way to study the brain enough to discover when that's the case, who would be considered to have a mirror-image view of reality? I don't believe that we could say either way, since each person's views of reality are internally consistent, and would make all the same predictions about reality. There's just no way to determine if the universe is actually this way or that way. Construct a model of the universe, and look at it through a mirror (don't try this at home, it's far too big.) Everything still works normally, since you're looking at the same thing, but certain rules are changed. The right-hand-rule for vector multiplication in electromagnetic interactions would become the left-hand-rule, the parity violation of weak interactions would cut the other way (I think that's how it works), etc. The question instead becomes whether the universe makes a choice here, or if reality doesn't actually have a preference in the left/right placement decision, and outside of our minds the structure of space is something bizarre and foreign.

4 comments:

Flushy McBucketpants said...

um. i'm pretty sure that if left and right were subjective, that traffic laws would be rendered useless. remember that everyone seems to agree on which side of the road is right and which is left for driving purposes... just for example.

i think you should look at color and right v. left not so much as personal subjective experiences, but as social conventions.

aducore said...

What I meant is, more or less: imagine you grew up your whole life as though you were looking at the world through a mirror. While, to you, you would feel like you were driving on the 'other' side of the road, it would also seem like everyone else is too. While you would read 'backwards', all of the books you find would also be printed 'backwards'.

I'm not saying that there's confusion in reality about what's left and what's right (obviously most of us drive on the correct side of the road,) but that in one's mind, they may be represented as mirror images of what they are represented as in another's mind.

Social conventions aside, you have a certain representation of space in your mind. While the words 'left' and 'right' are entirely arbitrary, they name two distinct and identifiable regions in your perception. The two sides don't just feel different, so that you could say that two things aren't on the same side of some other thing, but they each have some distinct and identifiable representation in your mind, so that if you're shown an image with two things next to each other, you could name which is to the 'left' and which is to the 'right', and you could do that consistently. Whatever you name them, there's still 'the side that has the hand you prefer to use', 'the side of the bed you sleep on', or 'the side the sun rises when you face the north pole', etc. What I am saying is that perhaps if you were to somehow step into another persons mental representation of reality, everything would be a mirror image.

Benjamin Storer said...

Many studies have been performed which alter the light entering the eyes, by rotation, inversion, or even curving what should have been straight lines. The general consensus is that after a reasonably short amount of time, there is no trouble properly perceiving what is seen. Some of the studies that flipped everything upside-down stated that the subjects no longer saw everything as being upside-down, others disagree. But they say this is more a result of knowing what is "correct," i.e. what it looked like before the subjects put on glasses.
I can't get access to the studies here, but you probably could track them down at UMD's library or on one of the article searches. Check out Stratton's Vision without inversion of the retinal image (Google Books has the third collected edition of Psychological Review, which has some initial thoughts, but I can't find the one with this specific article), or Snyder and Pronko's Vision with spatial inversion, or Ewart's A study of the effect of inverted retinal stimulation upon spatially
coordinated behavior
, or Dolezal's Living in a world transformed.

aducore said...

Interesting stuff... I'll have to check the rest when I'm on campus tomorrow.

I'm going to have to see if any of these studies looked at things like reaction time for identifying letters rotated through 0-360 degrees, or try that experiment myself. Depending on how those results would look, you could probably figure out what point along the visual pipeline this neural plasticity is apparent.

I wonder if, initially, there is some basis for what side goes where. I'd imagine it could be genetically influenced, or just decided at random... maybe left handed people and right handed people feel like they're using the same hand, but their representations are mirror images of each others... That would let the neural circuitry for controlling the dominant hand be more hard-wired to perception, which could be a benefit (or not, I'm not a neuroscientist.) Maybe men and women? republicans and democrats? emacs/vi people?

I still think that the most mind-bending aspect of this whole thing is that there's no real reason to think that space follows your own L/R choice, and that that question may not even make sense.