Lessons from Optical Illusions

Optical Illusions warn us not to believe our eyes – what we see is actually not the truth! Besides using them to impress people with such simple magic acts, there are more lesson for us.

I first come across such optical illusion diagrams when studying ergonomics in engineering school.

What do you see?
The upper line is shorter than the lower line.
The same effect is created whether I use the arrows or the circles!

Even when I tell you that the lines are actually of equal sized, we still see them as one longer than the other. Our perception is some how distorted by presence of additional lines or circles.

However, if I introduce some key guide lines for comparing their sizes as shown the picture below, we can see very clearly:

What lessons can we learn from these diagrams?

Here are my suggestions or interpretation or implications:

  1. Additional information(represented by the arrow heads or circles) distorts our perception of the truth
  2. There are such things call misleading facts. Facts presented to distort the perception of truth.
    These are what the con man do to us. They present facts to lead us to draw our own conclusion that they set up.
  3. Getting additional information or facts may mislead us in drawing a wrong conclusion. Statisticians warn us that association may not reflect the cause and effects.
  4. Pruning away misleading facts help us to see clearer.
    If you can, take away the arrows and circles from the above diagram and you can see clearly for yourself.
  5. It is difficult for us to be objective.
    Our experience and mind-set has great influence in our perception of things. We have the famous saying of ‘we only see what we want to see’. Even though we know the lines are of equal sizes, we don’t see it!
  6. Look for guides or references or standards to help us ascertain the truth. (by drawing the vertical lines). When it is difficult for us to ignore the presented information, we want to use reference or guideposts to help us find the truth.
    e.g. when some money is mistaken transfer from one account to another.
    How can we tell it is an honest mistake or a intention stealing?
  7. Don’t Over Generalized
    Don’t get carry away to generalize that because information may distort there is no need to look for more information. This exercise just warn us that information may help clarify or distort. We need to be wiser.
  8. Recall from Stats that there are two types of error in drawing our conclusions
    • Type 1 false positive: saying it is a virus when it is not.
    • Type 2 false negative: saying it is not a virus when it is a virus.


When reading the news and posts of the social network, I should be

  • not to believe all of them as true. There are hoax, spam, disguised advertising and sabotages.
  • careful not to prejudge or be too quick to jump to conclusions.
  • know that I am prejudiced by my experience and mindset and need to seek multiple points of views.
  • have guide posts type of criteria to seek for more information and for filtering to get to the truth.
An example of non-intentional misleading conclusion can be seen at Fooling Ourselves and Others with Stats – Fertility Rate …

Lim Liat (C) 8 Jan 2013

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