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When Being Smart Isn’t Enough: Shephard’s Tabletop Illusion - Part 2

APICS Senior Director, Professional Development

Monday November 14, 2016


Are these tabletops identical? Of course not, one is much more narrow than the other – right?

Well, actually, they are identical.  Don’t believe me? Watch this 21-second video: https://youtu.be/t2n3dBiN8R8

So, now that you’ve seen the video, they look identical, right? As it turns out, no, they don’t.

This illusion was first presented by the US psychologist Roger Newland Shepard (born 1929) in his book Mind Sights: Original Visual Illusions, Ambiguities, and Other Anomalies (1990, p. 48).

In his book, Roger Shephard notes that an intellectual understanding that the two table tops are identical in size and shape does not help you see them that way.

“. . . any knowledge or understanding of the illusion we may gain at the intellectual level remains virtually powerless to diminish the magnitude of the illusion.” -Roger Shepard, Mind Sights, p 128

Why does this illusion fool you?  We are built for a three-dimensional world.  We have no experience in anything but a 3-D world.  When we see the two tabletops, we automatically convert the 2-D image on the page to a 3-D interpretation of the tabletop shapes as they must be in the natural world. And we accept this illusion unquestioningly. So much so that we can never see the tabletops as identical, even when, intellectually, we know that they are the same.

Cognitive biases, which come from our unconscious, are just as impossible to see while they are in action as it is for you to see these tabletops as being identical, even after it has been objectively shown to you.

It is very difficult to convince ourselves that our intuitive experience is incorrect, even when confronted with strong evidence to the contrary.

Let’s take a quick look at one of the most devious biases that we have.  It is the Confirmation bias.

We want to be right about how we see the world, so we are careful to base our opinions on years of objective analysis – right?

Well, no. It turns out that our opinions are a collection of information that we choose to pay attention to.

Confirmation bias causes us to seek out information that conforms to our current beliefs and discounts everything else. If you believe that a new product line that you are considering will be a great success, then you will tend to look for data that agrees with this assessment and will discount or deny data that is not consistent with that point of view.  Another example is only going to news sources that support your political beliefs. Do you follow Fox-TV or a CNN?

The reinforcement we get from “being right,” (remember the activation of the brain’s reward circuitry I mentioned in my last blog?), motivates us to seek out situations in which we feel we are right. More importantly, it motivates us to not seek out information suggesting that we might be wrong, and even ignore uncomfortable information right in front of us.

I’m sure that you have seen, as I have, two people with diametrically opposing views watch the same political debate and declare, when it was done, that their candidate had won the debate.

So, how do we combat Confirmation bias? We purposely broaden our sources of information and be mindful about the information that we take in.  Balance your opinion with various viewpoints. Purposely search for information that you don’t agree with.

You can tell how well you do this by checking your Favorites or Bookmark lists in your browser.

By the way, do the tabletops look identical yet?

More posts in this series

When Being Smart Isn’t Enough: The Blind Spot Bias - Part 1
When Being Smart Isn’t Enough: Texas Sharpshooter Fallacy and Seeing Patterns in Data - Part 3

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