2019-02-01_Popular_Science

HEAD TRIP

SHAKE IT

you move,

i move

118 SPRING 2019 • POPSCI.COM by Sara Kiley Watson

LOOK AT THE PATTERNED IMAGE

above. With the magazine fixed, the design re-

mains still. But move the page ever so slightly,

and the decorative display picks up speed.

What’s driving this delusive dynamism,

says neuroscientist Stephen Macknik at SUNY

Downstate Medical Center in New York, is our

mental attempt to focus on a moving world.

When our eyes concentrate, they gener-

ate tiny jerklike twitches known as micro-

saccades, which alert our brains to motion.

To prevent the world from seeming like a

giant strobe light show, we suppress these

movements, keeping the eye seemingly still.

But the image above hijacks this system. In

the real world, sharp changes between light

and dark signal movement. The picture here

mimics this, as a light shape offsets a dark one.

Also, each inside circle is rotated 90 degrees

compared with its outer one, making the inner

and outer circles quiver in polar directions.

Our never-ceasing microsaccades pick

up on these contrasting colors as action and

send that information, via motion- detecting

neurons, to our brains. Our noggins then nat-

urally suppress the microsaccades but retain

the movement signals. So what you end up

seeing is an endless continuum of false flux.

Of course, to make it cease, you can always

stop wiggling the page around.