Do you see this image as moving? So does almost everyone. This is a visual illusion. In fact, if you take a minute and look closer, you can see that the boxes remain static. What about these classic illusions?
I have always been fascinated by visual illusions. Even after the trick is revealed, if you take a step back and look again, you are once again fooled. It has rightfully earned the term ‘Illusion’!
It is reasonable that the very first thought you gather after witnessing these illusions would be WHY?.
Why do we see visual illusions?
The answer seems to not reveal itself easily, either. A popular opinion is that it is a result of our visual experience. We are tasked to navigate a 3-D world, where different objects have varying depths. When exposed to 2-D lines (The white lines placed on top of the image) upon real-world images (Rail-road), like the one used for Muller-Lyer Illusion,(a) in Figure 2. We try to interpret these 2-D lines , based on our ‘visual experience of this image in our 3-D world’. The takeaway would be- visual experience influences our perception of how these imaginary 2-Dimensional lines we are measuring would be represented in our 3-D world.
While the role of experience has been the general assumption, recent researches have been coming up with conflicting views. The argument takes a polar opposite stand- claiming
visual experience do not play any role in it, and rather these illusions are driven by processing mechanisms in our brain.
The evidence for these claims come from the brilliant ‘Project Prakash’, which aims to treat curable blindness in India while illuminating interesting scientific questions for when the brain gets back its vision. Blind children reinstated with their vision, i.e. lacking any visual experience, were susceptible to visual illusions too!
While the answer for a WHY still evades the light of scientific inquiry, visual illusions are a fascinating yet grim reminder to humankind that our brains are not as reasonable and objective as we would like it to be.
“No, our science is no illusion. But an illusion it would be to suppose that what science cannot give us we can get elsewhere.”
― Sigmund Freud, The Future of an Illusion
References
- Project Prakash, web.mit.edu/sinhalab/prakash.html.
2. Gandhi, T., Kalia, A., Ganesh, S., & Sinha, P. (2015). Immediate susceptibility to visual illusions after sight onset. Current Biology, 25(9), R358-R359.
