Our brains are not perfect; they can be fooled by the simplest of drawings. Take this picture for example.

The lines are crooked, right? Nope! They are perfectly straight in reality, the staggered checkerboard pattern just gives the illusion that the lines are angled.

Visual illusions are defined as “dissociation between the physical reality and the objective perception of an object/event.”¹ Essentially, we might see objects that aren’t there, or we may fail to see objects are. The truth is, the same neural machinery that interprets our visual, auditory, and other sensory inputs also handles our dreams and delusions. They share a physical space, so it is no wonder they get confused! The disconnect between reality and what we perceive when looking at optical illusions can be a good thing though; the mistakes allow scientists gain a better understanding of the brain and how it constructs visual experiences. Let’s get into the neuroscience.

Everything we see in our lives must be interpreted by the brain. However, these interpretations can occasionally go awry, as seen with optical illusions. There are lots of different types of optical illusions, and the neural mechanisms behind these different types differ. Lets use the following optical illusion as an example:

This optical illusion is within the “illusory motion” class, meaning the something about the image (i.e color or object orientation) causes us to perceive motion within the picture. The motion is obviously not there, but we think it is a result of our small eye movements/vibrations. When we move our eyes, we perceive the visual world in a new way, and this new representation of the world in our brains is actually creating the movement in the photo. Want proof? Look at the image closely and focus very hard on a single brown object in the background you will see that the motion stops!

Our visual system processes motion, color, orientation, and more. As a result, there are tons of different types of illusions that can trick you into perceiving motion when there is none, perceiving two colors as being different when they are not, or incorrectly perceiving the orientation or angle of something (as we saw in the first checkerboard illusion). There is information about every type of illusion, but it would be impossible to go on about every one in this blog post! To end, check out some of these cool illusions and anamorphic/3D drawings!

See more of these amazing 3D drawings at http://www.gizmodo.com.au/2015/02/thesecool-anamorphic-drawings-will-play-with-your-brain/

Sources:

1. http://www.scientificamerican.com/article/the-neuroscience-of-illusion/
2. Eagleman, D.M. (2001) Visual Illusions and Neurobiology. Nature Reviews Neuroscience. 2(12): 920-6.
3. http://www.quora.com/How-do-optical-illusions-work
4. M. Glasser, J. M. G. Tsui, C. C. Pack, D. Tadin. PNAS Plus: Perceptual and neural consequences of rapid motion adaptation. Proceedings of the National Academy of Sciences, 2011;
5. http://www.gizmodo.com.au/2015/02/thesecool-anamorphic-drawings-will-play-with-your-brain/