New study debunks myth about popular optical illusion (Update)

December 21, 2010
Silhouette Illusion. If the foot touching the ground is perceived to be the left foot, the dancer appears to be spinning clockwise (if seen from above); if it is taken to be the right foot, then she appears to be spinning counterclockwise. Image: Wikipedia.

A psychology professor has found that the way people perceive the Silhouette Illusion, a popular illusion that went viral and has received substantial online attention, has little to do with the viewers' personality, or whether they are left- or right-brained, despite the fact that the illusion is often used to test these attributes in popular e-quizzes.

Niko Troje says that a reported preference for seeing the silhouette spinning clockwise rather than counter-clockwise is dependent upon the angle at which the viewer is seeing the image.

"Our visual system, if it has a choice, seems to prefer the view from above," says Dr. Troje. "It's a perceptual bias. It makes sense to assume that we are looking down onto objects that are located on the ground below us rather than floating in the air above us."

In the Silhouette , a silhouetted woman is seen spinning on one foot, her leg extended. The appeal of the illusion is in the way the woman is spinning – she can be perceived as spinning clockwise or counter-clockwise.

Dr. Troje and his team found that a view-from-above bias (VFA) is what makes the viewer prone to seeing the silhouette in a certain way, not one's personality or whether the viewer is left- or right-brained. When shown the silhouette illusion, the study's 24 participants most often reported that the woman was spinning counter-clockwise if viewed from above, and clockwise if viewed from below. Thus, the viewing angle causes the difference in perception.

Watch a video demonstrating the researchers' findings below.

The theory can also be applied to other popular illusions, including Neckar Cubes, that are often used in online tests.

More information:
-- The study was published this week in i-Perception, the new open-access sister journal of the established British journal Perception.
-- Silhouette Illusion:

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4.7 / 5 (12) Dec 21, 2010
What? you mean that those online personality tests aren't reliable? Does this mean that my personality might not actually be cyan?

1 / 5 (7) Dec 21, 2010
Soaking up another free earmark. And it took a whole "team" to do it too.
5 / 5 (1) Dec 21, 2010 do I know if I'm left brained or right brained? Can't they find another, more reliable optical illusion???
1 / 5 (1) Dec 21, 2010
If you're left or right brained you still have to pay the rent. I think anyone who sees her rotating anti clockwise should be burnt at the stake.
5 / 5 (1) Dec 21, 2010
Looks to me like she's falling over backwards, not spinning. It is in a pose that is unnatural for anything, especially spinning. The only thing that is true I see here is that it is an optical illusion, I can't tell if she is falling towards me or away.
3.4 / 5 (7) Dec 21, 2010
The idea that there is such a thing as "right" and "left" brained in completely asinine to begin with.
not rated yet Dec 21, 2010
Hmm. Noticed that it's possible to 'reverse' the perception of direction by allowing the image to float off into the peripheral vision. Got it to 'switch' directions twice doing so.
not rated yet Dec 21, 2010
Hmm. Noticed that it's possible to 'reverse' the perception of direction by allowing the image to float off into the peripheral vision. Got it to 'switch' directions twice doing so.

If you look to the opposite side, relative to her foot, of the box just as her foot reaches the closest point to either side, she'll rotate back and forth, but never around in a circle.
not rated yet Dec 21, 2010
I was also noticing that if you watch the toe of the grounded foot and imagine that the toe is pointing away from you at all times moving from right to left and back again, you can watch her pivot back and forth rather than spinning.
2.3 / 5 (3) Dec 21, 2010
this is the type of thing you don't need a study for. This is lazy, unnecessary and obvious science. But I guess it's good to debunk.
not rated yet Dec 21, 2010
People are awfully willing to accept "gods in the gaps" arguments (ie you didn't prove it's not true so it must be 100% true). I'd say proving the obvious has so real merit, not like it costs millions of dollars or anything.
3 / 5 (2) Dec 21, 2010
It seems to me that only 24 people is a very small sample, and then when they said "most often" the error starts to become pretty large. I'd say this is a useless study, both in scope and result.
not rated yet Dec 22, 2010
What does it mean if you're able to rock it left and right, so that she never has her back on you?
1 / 5 (1) Dec 22, 2010
"Thus, the viewing angle causes the difference in perception"...Utter Rubbish.
I agree the direction one sees the image spinning has little if anything to do with left-right brain biases and other popular myths but find the contention that viewing angle has anything to do with it equally ridiculous ie total rubbish. I see the image rotating in either direction and do not change viewing angle to do so and do not subjectively see any change in viewing angle.

The only viewing angle anomaly that I can see is when the image is viewed at an angle beyond the blind spot (eg left of the left blind spot). In this case no rotation is seen ~ the image is not interpreted as rotating so the image is seen as it actually is (pre-interpretation ~ if anything it looks like she's skating
not rated yet Dec 22, 2010
The reactions and comments for this article are almost a personality test example. Does anyone know of a classification system to place each commenter into an archetype?

I don't think the solution is quite as obvious as the angle. . . It makes sense that looking down or up at the picture has an effect as described. BUT, that doesn't explain variations in perception for the ambiguous angles. Does everyones perception shift at exactly a specific angle above or below horizontal with the eyes? if so does turning the body upside down or leaning forward or backward significantly affect the angle of ambiguity? Slumped over or sitting up strait?
not rated yet Dec 22, 2010
I think there could be some practical applications to identifying all factors that can affect perception. There's also an expectation bias and other things going on so once a precise understanding of the angle of ambiguity and a graph of nearby angles and probability of perception A or B is determined. . . Then you can precisely measure the expectation bias. Having a quantitive understanding of the expectation bias could be very valuable. Think stock markets if you're a competitive money person, think overcoming skepticism about global warming if you want a more cooperative example of how this could be useful info.
5 / 5 (3) Dec 22, 2010
That girl has an awesome body
not rated yet Dec 22, 2010
I watched the video several times. I see all three images starting off spinning clockwise when viewed from above. When the right image lights up, it spins counter-clockwise while the other two don't change. Does anyone else see it this way?
5 / 5 (1) Dec 22, 2010
The picture looks like someone walking away, not spinning.. what does that mean? am I doomed?!

2.3 / 5 (3) Dec 22, 2010
(The school psycologist) gives me a chocolate Easter bunny. And this shows how tricky those guys are. I eat the chocolate and I think, wait a second... this isn't around Easter.

"Was this a test?"

He said, "Yes."

"And what does it mean?"

He said, "Well, had you eaten the ears first you would have been normal; had you eaten the feet first you would have had an inferiority complex; had you eaten the tail first you would have had latent homosexual tendencies; and had you eaten the breasts first you would have had a latent oedipal complex."

I said, "Well, go on. What does it mean when you bite out the eyes and scream, 'Stop staring at me!'?"

Shamelessly stolen from comedian Emo Phillips
5 / 5 (1) Dec 22, 2010
yeh i can twitch it to if i blionk my eyes with a certain frequency
5 / 5 (1) Dec 22, 2010
It's clearly an adult woman and therefore it is a sexist study.
not rated yet Dec 22, 2010
Still doesn't explain why the illusion has a alien head.
1 / 5 (1) Dec 23, 2010
nice boobs!
5 / 5 (1) Dec 23, 2010
wow, and the trolls are out in force on this one.
not rated yet Dec 24, 2010
search "The Spinning Dancer's Mistery" if you want to find the explanation of this illusion.
not rated yet Dec 24, 2010
In the still image, she, in no way, appears to be rotating. To me, it looks like she's walking away with her left foot on the ground.

Also, the caption of the image and the video disagree with each other regarding which foot on the ground signifies which direction of rotation.

In the still, my mind made its determination based on what appears to be perspective. The lifted foot appears to be smaller, therefore, further away. Also the hand and ARM sizes didn't look right for an on-coming direction.
not rated yet Dec 25, 2010
The picture looks like someone walking away, not spinning.. what does that mean? am I doomed?!

It means you didn't click Enlarge and actually see the spinning image. XD
not rated yet Dec 27, 2010
The light source and projected shadow are critical 'cues'. The silhouette's anatomy (body parts)are contributing additionally to the 'cues' available ones perceives as well.

The more "reliable" 'cues' turn out to be, (whether the illusion depicts clock or counter clockwise motion or whether the figure is approaching or receding) the greater the 'bias' towards "reliable" cues become through experience. The reliance on experience is an illusion. Experience relies on environment. For example: no color of an object we 'perceive' here on earth will be the same color perceive on Mars. The definition of color remains unchanged.

As if Physics provides a perceive 'need' for a 'reference' that is absolute. Or 'reliable' reference.

There is no escaping indulgence. Nature's.

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