When Your Eyes & Brain See Differently…

Look to the left… This graphic seems rather unimpressive, right? Two lines with directional fins applied to them. You see the lines and your brain knows the lines are different. Thus, we accept the belief that, surely, the lines are of varying lengths.

But don’t call me surely… Get a ruler and measure the lines. You will discover the two lines are IDENTICAL in length.

Müller-Lyer illusion

This example, known as the Müller-Lyer illusion, is an instance of an illusory effect. Optical illusions such as this one present amusement, but also, emphasize how the brain and perceptual sub-systems work.

Some experts are of the belief we perceive the lines to be different due to a misapplication of the same process we use to determine that someone who is 6‘ 4” is taller than someone who is 5’ 9”. An alternative explanation is that the cues (the fins) present a conflict that our brain is unable to see past.

The human brain looks for shortcuts in helping make sense of the world around us. One of the ways it achieves this is by reflexively processing information like that highlighted in the Müller- Lyer illusion. While theories to explain illusions such as this continue to develop, they do prove that what our eyes see is not always what our brain processes.

This was Article 5 from the Studio Quick Facts Series.


Works Cited
Chabris , C., & Simons, D. (2009). The Invisible Gorilla: How Our Intuitions Deceive Us. Harmony.

Gigerenzer, G. (1991). How to make cognitive illusions disappear: Beyond “heuristics and biases”. European review of social psycholo- gy, 2(1), 83–115.

Kahneman, D. (2011). Thinking, Fast and Slow. Farrar, Straus and Giroux.

Vanderbilt, T. (2009). Tra c: Why We Drive the Way We Do (and What It Says About Us). Vintage.

Weinschenk, S. (2011). 100 Things Every Designer Needs to Know About People (Voices That Matter). New Riders.

Weinschenk, S. (2009). Neuro Web Design: What Makes Them Click? New Riders.