checker shadow illusionYour unconscious beliefs shape and distort your perception of what’s around you. Don’t believe this applies to you? This image, the ‘checker shadow illusion’ proves it does!

The ‘checker shadow illusion’ was developed by Edward H. Adelson, Professor of Vision Science at MIT in 1995. Take a look at it. Square A and square B are actually the same colour!

No matter how long you look at the image, your brain won’t see the two squares as the same colour. But they are – as you can demonstrate if you add two stripes of the same shade of grey that intersect both squares:

checker shadow illusion revealedWhen I viewed the original image on my phone, I didn’t believe it myself until I used an ‘eyedropper’ app to sample the RGB values of the two squares and found they were both RGB (120,120,120). You can try this yourself with an online colour picker such as the one at

How on earth does this happen? Professor Adelson’s brief, non-technical explanation of why the illusion works is here.

Researchers into the science of perception have found that our visual systems use various ‘quick and dirty’ rules to break down the barrage of visual information that they receive into meaningful outlines of objects.

Most of the time these rules of thumb work well, but sometimes they lead to us seeing what we expect to see rather than what is actually there.

Similarly, our minds unconsciously filter and distort incoming information of other kinds so we perceive what we expect to be there, rather than what’s actually there. This leads to a number of different ‘cognitive distortions’, the most obvious being ‘confirmation bias’ – we play up information that confirms our beliefs, and play down or ignore information that doesn’t fit.

This shows up in a number of ways. There’s a general election campaign going on in the UK at the moment, and it’s noticeable how people will only notice good things about ‘their’ chosen candidate, while not even noticing, or at least explaining away, any mistakes, flaws or evidence of incompetence or wrongdoing. At the same time they sieze on and magnify any misstep by the ‘other side’.

If you like someone, you will tend to believe that they have other good qualities, before the evidence is in (the ‘halo effect’). If you have an image of a team member as incompetent, it will be very hard for that person to impress you, even if in reality they’ve turned over a new leaf and start performing well. If you expect a change to be unpleasant, your mind will be filtering for every bad thing that happens and ignoring any positive aspects.

How can you guard against these cognitive distortions? It’s not easy, especially as we have a desire to be consistent: once we believe something, we find it uncomfortable to change our minds and will resist or explain away new information that doesn’t fit. No-one likes to be wrong.

A good way to get round this resistance is to treat events that don’t fit our expectations or pre-existing beliefs as ‘surprises’ rather than as ‘being wrong’. Keeping a ‘surprise journal’ reduces our resistance when we find that our beliefs don’t fit the evidence.

You could also actively look for counter-examples to whatever you believe. Most, perhaps all, generalisations have exceptions. Actively looking for counter-examples will remind you not to treat your beliefs and expectations as absolute truth.

Finally, here’s a way to make cognitive distortions work for you, or at least to free yourself from the negative emotional effects of beliefs that aren’t serving you. If you expect the worst, you will be scanning constantly for bad experiences, which will lead to ignoring anything good that happens and missing out on experiences of joy, to feeling anxious about the future, and feeling resistant and resentful about change.

Instead, view the possibility that things may go badly with detachment, while at the same time actively looking for evidence of positive change. Remember what you have achieved, what you are proud of, and the difference that you and your team have made. This will make you feel more positive and optimistic, which makes it easier to access your inner resources and actually makes you think more effectively.

You will also be more inspiring to others around you, and contribute to a positive ’emotional climate’ in your team.

The above images are ©1995 Edward H. Adelson. These checkershadow images may be reproduced and distributed freely.

If you’re a trainer, the checker shadow illusion is a great learning aid to demonstrate that our unconscious beliefs distort our perceptions. Some colleagues have told me that they occasionally get a learner who refuses to believe that squares A and B are the same colour. So here’s a simpler image (from that demonstrates the same point – but that learners can easily verify for themselves by covering the join between the two squares with a finger.

identical colour illusion

Your Unconscious Beliefs Distort Your Perceptions – With Proof!

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