This side up: Perceiving visual orientation

This is a guest post by Aaron Couch, one of Greta's top student writers for Spring 2007

i-eca0cf2af9fc3ac4445c7dff7d8aab70-research.gifWhen looking out a window, or watching a movie in a theater, the image you see is typically presented as right-side-up. Let's say though, that you're lying on your side in bed and looking out a window at your backyard. Both your internal gravity sense organs and the orientation of scenery (trees, buildings) tell you that you're actually seeing a "tilted" image, and your mind immediately tells you which part of the scene is "up".

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In a similar vein, a team led by Ian P. Howard performed research that challenged our mental "visual-righting" system by placing perceived images and our gravity sense organs in conflict. In their research, participants laid down on a bed and looked straight up. Directly above them was a mirror, tilted to display the wall behind them. So, with their own eyes, the person was looking "up" at a ceiling, but the mirror reflected an image presented on the wall.

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An image was projected onto the surface the participant was viewing. Two sets of scenes were shown, some with intrinsic polarity (apparent "up" and "down" directions), like an upright chair or human manikin; and a second set to investigate extrinsic polarity, such as a shelf, a ball on a shelf, and a ball "under" a shelf. When presented with the chair or manikin, most people believed they were actually looking directly at a right-side-up scene, or a "wall" in front of them, although their eyes and body were facing upwards. The presented visual scene took precedence over the viewers' gravity sense organs!

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Notice however that an unnatural visual situation, such as the ball directly under a shelf, does not indicate the rules of gravity. Therefore, more viewers saw this "correctly" as an image on the ceiling above them. On the other hand, a ball sitting on a shelf shows a natural situation, implying the presence of gravity and therefore, uprightness.

In a visual-righting illusion your gravitational senses override your visual perception, whereas in a levitation illusion your visual senses override your gravitational perception. According to Howard's team, some of the most interesting real-life situations of misperceived orientation occur for astronauts in space. Imagine flying back to earth in a shuttle and seeing earth "above" you when you are in reality upside-down. This provides somewhat of a parallel to visual-righting and levitation illusions, except that for astronauts, the absence of both gravity and visual orientation really throws perception into a bind. But then is there really such a thing as "up" or "down" in space?

Howard, I., Hu, G., Saxe, R., & Zacher, J. (2005). Visual orientation in a mirror world tilted 90°. Perception, 34, 7-15.

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Hmmmm, all I know is that when I run into instances like those mentioned above, I get nauseated and dizzy and become slightly disoriented. Once when I was at Bryce Canyon National Park there was a creek that looked like it was flowing upstream (even though it really wasn't) and I could not look at it longer than a few seconds before I felt the nausea. No way I would ever make a decent astronaut. To me up has to be up and down has to be down, and when they aren't, or there is an optical illusion, I get very nauseated and disoriented. Wonder if that has anything to do with my motion sickness also.

By roseindigo (not verified) on 05 Jun 2007 #permalink

When presented with the chair or manikin, most people believed they were actually looking directly at a right-side-up scene, or a "wall" in front of them, although their eyes and body were facing upwards. The presented visual scene took precedence over the viewers' gravity sense organs!

I'm afraid I don't quite understand this -- did they believe they were not lying down? Or did they just confirm that they were looking at a reflection? What is the significance of them thinking the "wall" was "in front of them," rather than behind them? Were they told that there was a mirror above them, or were they told that there was not a mirror above them, or were they told that there may or may not be a mirror above them? Was each participant shown two scenes, one with intrinsic polarity and one without, or was each participant shown one or the other? Or a randomized series?

The enemy's gate is down.

In response to Jay's inquiry, the participants were helped into the foam padded bed with their eyes closed. Of course the viewers were aware that they were lying down flat, however they were reporting on the perceived orientation of what they were viewing. The mirror covered 116 degrees of the participants visual angle, and they were unable to see their own bodies, but it is unclear from the experiment whether or not the viewer was informed that they were looking at a mirror.

The full article is available at this link (PerceptionWeb).

I have to relate an interesting personal experience that happened to me in the past, probably five(?) years ago. I had been sleeping on one side, in my own room. At some point my eyes opened so that I was conscious of my surroundings, but still asleep- it was like I was dreaming that I was standing in a room that looked exactly like my bedroom, except turned on its side. I believed myself to be standing upright, and couldn't figure out why I was having such difficulty walking. .. until I took a "step" and fell out of bed, which woke me up.

Yeah, weird, and not exactly analogous, but thought you might find it interesting.

From an evolutionary psychology perspective our visual system does take precedent over body orientation. However my question is would the image still take precedent if the subject/participant was hung upside down? Is there a maximum angle of threshold in which if exceeded would allow the subject to sense the orientation over the visual perception?

In response to roseindigo's comment, "I get nauseated and dizzy and become slightly disoriented," you would feel nauseated and dizzy when your visual system and your vestibular system (located in your ear) are inconsistent. Such as when you spin around in a circle and stop you become dizzy because your visual field has stopped but the organ inside your ear that indicates orientation doesn't stop right away because it's a liquid system. That's the conflict of bodily sensations that creates dizziness.

My suspicion about whether the participant knew there was mirror in front of them is that they didn't. Because if they knew that it was a mirror, they would have reported seeing themselves in the mirror along with the relation of them and the background image that they see, which is not possible.

Lastly, this is so interesting to philosophize because personally I can't think of an incident when I got dizzy with my eyes closed.

Is this internal sense of "up" responsible for our perception that text flips left to right when viewed in a mirror but not top to bottom?

By Arbitrary (not verified) on 07 Jun 2007 #permalink

Chenru, I understand your explanation and it makes sense as far as motion sickness.

However, there have been instances in which bodily motion plays no part at all, like in an "optical illusion" cabin at an amusement park where the floor seemed to be slanted upwards, with windows were aligned in strange ways and all the furniture was askew. I was one of the people who had to leave because of the nausea.

So your explanation tells me that the two phenomena are not the same. OK, I can buy that. :-)

By roseindigo (not verified) on 07 Jun 2007 #permalink