A few months back I came across this spinning dancer. This visual illusion was created in 2003 by the web designer Nobuyuki Kayahara by combining 34 frames. At any point of time, you will see the dancer revolving either to her right (clockwise) or to her left (anti-clockwise). Sometimes, as you are watching, the dancer switches the direction. It looks as though you don’t have any control either on the direction of movement or on when it will reverse. Can I do the switch in the direction voluntarily? That is what I tried to explore past few weeks. The other question that came to mind was: To get convinced that it is an illusion, do I have to see the reversal?
Here are my observations when I watch it on the spinning dancer Wikipedia page on my laptop. My dominant direction is clockwise. However, when I watch the picture by almost closing my eyes when the picture becomes blurry and I see the movement of legs as almost two dimensional, I am able to switch the direction. It is almost voluntary though not guaranteed. When I copy the image on PowerPoint slide or on phone, the speed of rotation is slower compared to the laptop. And there I find it harder to do the voluntary reversal by blurring my vision. When I scroll the image up so that only her feet below knee are visible, then sometimes I perceive the dancer dancing like a pendulum – little to the left and then little to the right but not going full circle. But as soon as I scroll the picture down, the dancer starts rotating full circle. Again, all these changes are involuntary. You can see how other people perceive this by reading the comments on this New York Times article “The truth about the spinning dancer”. Can we explain this using Daniel Kahneman’s fast and slow thinking modes?
One of the hallmarks of fast thinking is that it is involuntary – automatic. When I look at the dancer, I see the rotation either in clockwise or in anti-clockwise direction. I don’t have a choice here. This is a case where fast thinking mode is at play. Moreover, there is no direction inherent in the images that pass by. The three dimensional perception of the two dimensional images is created in the brain automatically. Certain set of neural circuitry is firing automatically, resolving the ambiguity of direction one way or the other and showing the rotation. This type of illusion is called a bi-stable visual illusion where there are 2 stable states – clockwise dance and anti-clockwise dance.
The fast mode of thinking is doing two key substitutions here. One, the direction of dance where none exists and two, the 3-D depth of the vision from 2-D images. Doing such substitutions to suppress ambiguity is a key characteristic of fast mode of thinking. They are happening all the time and we are not even aware of it. That’s how we are enjoying the movies on TV. Now, imagine a political party whose leader sees this lady dancing only clockwise. Never sees it anticlockwise. And then he declares those people who see it as clockwise as pure-blood and those who see it as anti-clockwise as mud-blood (to borrow Harry Potter terminology). And soon a fight follows which results in the flow of blood which has only one colour – red.
You might say that’s stupid! How can people fight over an illusion like this? Question is, how can you know it is an illusion if you don’t see it any other way (only clockwise)? Enter the second mode of thinking – slow thinking. As the fast mode of thinking is creating impressions and judgments like a mental shotgun, the slow mode of thinking can create a doubt and unbelieving. It can ask: could this impression be wrong? Then it can mobilize attention to gather more evidence (e.g. ask other people) and then make a more informed decision. The part of slow thinking which raises this doubt, is sometimes called the reflective mind.
Keith Stanovich a major advocate of the reflective mind theory, explains “Why do smart people do stupid things?” He says sometimes a person with high IQ (e.g. SAT score, education from top university, top rank in an organization) may still have a weak reflective mind. In that person’s mind, the question: Could this impression be wrong, never gets raised. In fact, Stanovich’s research on confirmation bias (or Myside bias) shows no correlation between SAT score and the bias tendency.
In short, fast mode of thinking is doing a fantastic job of automatically supressing ambiguity. But in the process it can also be creating illusions which are sustained (like the direction of the dancer). Reflective mind is an element of slow thinking whose job is to doubt the impressions and ask, “Could this be wrong?” We don’t need this as we go about our daily routine of brushing, driving etc. But perhaps when we are labelling somebody wrong, it is worth stretching the reflective muscle.