Directional Bias

[jducoeur]

I noted this morning how curious the human reaction to a mirror is. Some 35 years after learning to brush my hair in the mirror, the left-right error still sometimes throws me off when trying to manipulate things away from my body, and I have to consciously compensate for it. Which is odd, given that there is no such up-down confusion -- that's entirely intuitive. The mirror is doing the same thing in both respects, but we visually parse it *very* differently: up-down is easy and natural; left-right isn't. (I think -- I assume I'm not terribly unusual in this.)

There must be some neurological basis for this lateral bias in human vision -- having to do with the evolution of stereoscopic vision, maybe? -- but I don't know what's going on there...

Comments

[tpau]

oh good, it isn't just me. most times it is all good. sometimes i end up trying to brush my hair with the wrong side f the brush or on the wrong side.

[cellio]

It's not just you. And knowing, intellectually, that mirrors don't reverse left and right (they reverse proximity) doesn't really help me instinctively.

[metahacker.livejournal.com]

BTW, mirrors "really" flip things in the in-out direction. It's just that our brains decide the easiest rotation to get there is around the vertical axis -- with a horizontal flip to make details work out right. For brain-breaking fun, try to decide that the man in the mirror is you, just spun around a horizontal axis parallel to the mirror, and then flipped vertically. (It may help to lie on your side while attempting to thus hack your brain.)

We're used to seeing things rotate in the plane, and we're bilaterally symmetric, and we have horizontal binocular vision, all which I think push toward rotating in the vertical axis.

[siderea]

Right. When you look in a mirror and see a smudge on the left side of your face, you don't accidentally reach for the right side of your face to wash it off. It's in-out aka proximal-distal which is confused.

[baron-steffan.livejournal.com]

Okay. Maybe that's true, maybe it isn't. I have no way to judge because my entire brain just snow-crashed. I have no idea what you're trying to say here. Can you maybe elaborate, or paraphrase, or...something? I'm trying to visualize optical rays, but it isn't working.

[Scratching head][Miss-Teen-South-Carolina-voice] I don't get it.

[metahacker.livejournal.com]

When you look in a mirror, the direction that is reversed is the in-out direction. What you see in there is a mirror image of this world -- but not flipped left-right, flipped front-back. If you are facing north and looking at a mirror, your duplicate is facing south. Your left hand points west; his 'left' hand also points west. It's just that his left hand has its palm and back reversed, from your point of view.

However, our brain really doesn't like thinking about inversion that way. We are much more familiar with turning around and *facing* south. So we imagine that the duplicate in the mirror has also turned around; we think it is his *right* hand that is facing west. We imagine he is just like us, except that he turned 180 degrees around the "up" axis.

But there is a problem with this, if you try this with a non-symmetrical thing, let's say a snail. When we turn the snail around in our head, it looks backwards. So what our minds decide is that the duplicate snail is turned around, and then 'flipped' left-for-right, because this is somehow easier to imagine than the truth: it is flipped front-to-back.

What I was suggesting was that you could also achieve this result by turning the snail over in your hands, around an axis that runs from your left hand to your right, and then flipping it top/bottom. This is hard to imagine.

[fitzw.livejournal.com]

The thing that throws me off is rotation, not left-right. I need to rotate an object towards me, but I almost always rotate it the wrong way first.

[rosinavs.livejournal.com]

There are reasons I don't use mirrors very often except for makeup, which, well, I don't use very often.

[baavgai.livejournal.com]

Yep, no getting used to it.

Hair isn't so bad for me, that's really just a exercise in getting it out of the way. However, beard trimming...

Trimming a beard in a mirror is like trying to use robotic arms whose controls change at random moments. It never fails to confuse.