Saturday, February 14, 2009

Optical Illusions and the Illusion of Love!

This is the seventh article in the Mind Matters series on the neuroscience behind visual illusions.
It’s Valentine’s season, which means that everywhere you look there are heart-shaped balloons, pink greeting cards and candy boxes filled with chocolate. But what is true love? Does it exist? Or is it simply a cognitive illusion, a trick of the mind? Let us count the ways. Contrary to the anatomy referenced in all of our favorite love songs, love (as with every other emotion we feel) is not rooted in the heart, but in the brain. (Unfortunately, Hallmark has no plans to mass-produce chocolate-covered arrow-pierced brains in the near future.) By better understanding how the brain falls in love, we can learn about why the brain can get so obsessed with this powerful emotion. In fact, some scientists even see love as a sort of addiction. For instance, neuroscientist Thomas Insel and colleagues at Emory University in Atlanta discovered that monogamous pair bonding has its basis in the same brain reward circuits that are responsible for addiction to drugs such as cocaine and heroin. Their study was conducted in the prairie vole, a small rodent that mates for life. But the conclusions are probably true for humans, too, which may explain why it is so hard to break up a long-term romantic relationship. Losing someone you love is like going through withdrawal.
This month’s slide show features a number of visual illusions with a romantic motif. We hope that you and your special one will enjoy them. And remember, even if love is an illusion, that doesn’t mean it’s not meaningful and real (to our brains, anyway).

Pop! Goes My Heart
Nothing is more romantic than curling up in front of a fire with your loved one on Valentine’s Day, as you lovingly whisper, “chromostereopsis.” Okay, maybe it’s not as passionate as a sonnet—unless you are a vision scientist. Look at the red and blue hearts and examine their depth with respect to the background. Most people find that the red heart pops in front of the blue background whereas the blue heart sinks beneath the red background. This illusion comes about because our eyes’ lenses refract blue light more than red. This phenomenon is called a chromatic aberration; another example of this effect is seeing a rainbow when you shine white light through a prism. When both eyes view the red and blue images simultaneously, the cornea and lens of the eyes refract different amounts of the colors, which results in their systematic and symmetric binocular mislocalization. The brain deals with this sensory aberration by imagining depth—the red heart is in front of the blue background and vice versa—even though none actually exists.

Illusions That Move the Heart
Your wandering eyes pull at your lover’s heartstrings. In this illusion, the heart appears to move and even pulsate as you look around the image. When your eyes move, they shift the retinal images of the white/black edges in the pattern, activating the motion-sensitive neurons in your visual cortex. This neural activation leads to the perception of illusory motion. Note that if you focus your gaze on a single point, the illusory motion slows or stops.

Illusory Neon Heart
Notice that the yellow fields inside of the heart appear paler than the fields forming the contour of the heart, which appear to be a darker shade of yellow/orange. Right? Wrong. Actually, all of the yellow fields in the figure are identical. Any differences that you see are all in your mind. This effect is called “neon color spreading,” because it resembles the effect of the light spreading from a neon lamp. The neural underpinnings of this effect are not yet understood.

Love and Hate
Even more ambivalent is this mirror-symmetric ambigram of love and hate. Talk about mixed feeling—we hope she brings a mirror on her Valentine’s Day date. There’s even a T-shirt available at

For Coffee and Tea Lovers
“Yuan yang" is a typical Hong Kong beverage mix of tea and coffee, and also a symbol of marriage and love. Sculptor Tsang Cheung-shing has united both concepts in a beautiful ceramic work, in which tea and coffee poured from two stylish cups meet and kiss each other.

Love Is All Around
Romance is not just a concept for humans and voles. This slide shows that love, and illusions, surround us all.

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