By: Wendy Langhans

Optical illusions can help us see more clearly.  That’s because what we perceive depends not only on sensory input from our eyes but also the rules and assumptions hidden in our brain.  Optical illusions are designed to uncover these assumptions.

Look at this example of an optical illusion and you’ll see what I mean.  The circle in the middle appears to leap out as a convex sphere while the circles on the right and left sides appear to curve inward as a concave hole.

And if you rotate the diagram 180 degrees you’ll see an unexpected change: the diagram with two “inny’s” and one “outy” becomes a diagram with two “outy’s and one “inny”.  How did that happen?

It’s because our minds contain a visual assumption that sunlight comes from above our heads.  We assume that sunlight shines on top of an object and casts a shadow beneath the object.  In this optical illusion, our brain automatically picks up the shading cues, converting the diagram’s 2-dimensional circles into a 3-dimensional object in our minds.  These shading cues are what make the flat circles “pop out” as a convex sphere or “step back” as a concave hole.

Most of us have heard of camouflage, which is a technique animals use to blend in with their environment.  But camouflage is more than simply the colors and patterns that we normally observe; it also takes into account our visual assumptions involving shading.  Take a close look at the photograph of this caterpillar and note the dark stripes on the top that help disguise it from a top-down perspective. 

Now image you are a bird, hopping around in the underbrush, looking for a morning snack.  You quickly scan your surroundings and get a side view of the caterpillar: the profile of a dark back over a light belly. 

Will the caterpillar “pop out” at you or remain hidden the background?

In real life it’s more difficult to identify our assumptions because we are being bombarded with sensory data.  Take a look at these two photos of a Yucca.  They are identical except for their 180 degree shift in rotation.  Pay attention to the shading.  Which photo looks correct?  Which one looks slightly “off”?  Do you feel comfortable making a decision?

Suppose I added a fact:  Yucca blossoms tend to hang down.  Now can you see that the top photo is the correct view?

You have just used sensory data, previously-unrecognized assumptions and facts to make a decision.  That’s a good technique to remember and use, especially in an election year.

Upcoming Outdoor Events: 

Saturday, August 16, 8:00-10:00 AM.  Bird Hike in Towsley Canyon. 

For map and directions, click here. 

Sponsored by the Mountains Recreation and Conservation Authority.

Saturday, August 16, 7:30-9:30 PM.  Full Moon Hike in Towsley Canyon.

For map and directions, click here. 

Sponsored by the Mountains Recreation and Conservation Authority.

Saturdays, August 23, and every Wednesday, 8:00 am.  Trail Maintenance Volunteers at Towsley Canyon.

Come join our trail maintenance volunteers for camaraderie and a heart-thumping workout.  For more information contact Steve Ioerger at 661-291-1565.

Sponsored by the Mountains Recreation and Conservation Authority.

Through the end of August. Wildlands of the Santa Clara River Watershed.  Valencia Public Library. 

Come to the library to see a visual and educational exhibit about our Santa Clara River Watershed and the 100 endangered, sensitive or threatened species that live in our valley.

Sponsored by South Coast Wildlands, Visual Journey’s and the Santa Clara River Trustee Council.

You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.

For the complete MRCA hike and activity schedule and for trail maps, click here or go to www.LAMountains.com.