Rotating Snakes Illusion

July 28, 2014


In the Rotating Snakes illusion, subjects see what appears to be spontaneously rotating circular snakes. This type of illusion has been named a “Peripheral Drift” illusion, as the motion only occurs in your peripheral vision. When you focus on a circle, the rotation will cease. There hasn’t been evidence to show that a colored version is more effective than a black and white image. The main building block to allow this illusion to be effective is a sequence of four  elements of varying luminance; this would be a series of four colors beginning with a black (or darkest color) and ending with white (or the lightest color). Large scale organization is critical as the individual blocks to not evoke a sense of movement.

It is believed that the  four elements of luminance generate local motion signals. Studies have been done that measure the shape of temporal impulse response (TIR) function corresponding to the brightness of the stimuli. With the relative contribution of the transient component falling with decreasing brightness, researchers believe that transient factor of the TIR caused the strength of the illusion.

Retinal ganglion cells carry information to the retina to many different locations within the brain. There are two main categories of these cells, X and Y. X cells have an momentary response initially, but do not show sustained response to stimulus. Y cells respond faster and show more transient responses to the same stimulus. The receptive fields of these cells allow the cells to potentially decipher contrast within the illusion, but not the raw luminance.

Many participants of studies reported that if they focused on the imagine, the illusion failed. This shows that there is a need for the image to be refreshed by blinking or moving the eyes to sustain the illusion.



info from: Understanding the Rotating Snake Illusion by Martin O’Reilly

The Checker Shadow Illusion

July 28, 2014

In the picture, there is one square marked A and one marked B. At first glance, your visual system will determine square B to be a lighter color than square A, when, in fact, they are the exact same color. How does your visual system get tricked into thinking this?

The first part of the trick has to do with the squares around square B. Even though it is in shadow, square B is still lighter than its four neighboring squares. Therefore, even though square B is dark, it is light when compared to its neighbors. Outside of the shadow, the dark squares are surrounded by lighter squares. This makes them look darker in comparison to the square in the shadow.

In general, shadows have soft edges while objects like the squares have sharp objects. In order to avoid being misled by shadows, the visual system does not pay attention to gradual changes light level. Because square B is surrounded by dark squares, the visual system determines that all of B’s edges should be sharp edges, thus coming to the conclusion that its edges should be seen as changes in color rather than a change in light or shadow.

This optical illusion tells us that the visual system does not succeed at being a physical light meter. It generalizes visual information, takes what it has, and allows us to see the world in a way that is not always correct.

As you can see in the picture below, the two squares are definitely the same color:

Stepping Feet

July 28, 2014

Stepping Feet illusion:

  • Describe your optical illusion, what do we see/not see?
  •                  This illusion is to colored blocks traveling across a black and white striped back ground. By looking directly at on of the blocks you can see that it is moving non-stop across the background. But if you do not focus on the blocks but rather look somewhere on the background, you will see the blocks stopping and starting again at each black stripe.
  • Describe the neural bases of how your illusion works.
  •                 When there is a background with contrasted edges (black and white) our perception of the speed/ motion of an object over top of it is changed. But if we focus on the object instead of the back ground we see the constant motion.
  • What does your optical illusion tell us about the visual system?
  •                 This optical illusion tells us that our visual system is probably confused about what we are seeing. Our visual system is confused because the leading and trailing edges of the colored block are in two different backgrounds. So we cannot correctly perceive its speed.

The Leaning Tower Illusion

July 27, 2014



The Leaning Tower Illusion

Two identical pictures of the leaning tower of Pisa are displayed side by side. The towers are parallel. However, it seems that the picture on the right is leaning more than the picture on the left. Rather than looking parallel, the two towers seem to diverge farther apart in the distance. The explanation for this illusion lies in how our visual system interprets depth. We have 2-dimensional eyes, but we need to interpret 3-dimensional space, so our brain has to makes sense out of a distorted picture sent by the retina.

When our retina sees two parallel lines going off into the distance, the lines appear to converge. For instance, stand in the middle of a road and look down the road. The left and right edges of the road seem to converge in the distance. So, when our visual system sees two lines converging in the distance, our brains are hard-wired to interpret them as parallel. In the case of this illusion, our visual system sees two lines (towers) that look like they DON’T converge in 3-d distance. Thus, our brains actually interprets that these towers are diverging apart.

This illusion demonstrates how our brains have evolved to understand 3-dimensional space. Understanding space is crucial to navigating around an environment in search for food and whatnot. Thus, we are able to understand and sense depth in a 2-d image provided by the retina. When we see converging lines, our brains interpret the visual distortion and think parallel. However, this also means we can be tricked. The leaning towers are 2-d but they look 3-d. That causes the illusion to occur.


Alas, poor Yorick!

July 27, 2014

In the late 1800s, Pears Soap started a successful advertising campaign using an optical illusion. Named ‘Yorick’s Skull’ (for the jester who’s skull Hamlet famously holds) the illusion makes use of the effects of an afterimage.

Aside from being a staple in many optical illusions, afterimages are commonly seen in daily life (think of those dark spots in your field of vision after a bright camera flash). Afterimages are a result of our brain adapting to overstimulation. When exposed to a bright or unchanging stimulus for a length of time, the active photoreceptors in our retina become fatigued and lose sensitivity. As a result, when looking away from the stimulus, our retina takes a few seconds to adjust, causing the afterimage.

Some scientists also argue that prolonged exposure to an unchanging stimulus can cause the brain to expect it to remain unchanging. Hence, when it does change, we see the old image for a few seconds.

In the case of Yorick’s Skull, focusing on the ‘x’ in its right eye causes photoreceptors to lose sensitivity as they become fatigued. Additionally, the static nature of the image may cause the brain to believe that the image will not change. Hence, when we abruptly look away from the image, we can clearly see the skull’s afterimage for a few seconds.

(How this helped to sell soap remains ambiguous…)

Visual Illusion- Pareidolia

July 27, 2014

Pareidolia is an illusion, a visual phenomenon that occurs when a vague, undefiled stimulus is perceived as being distinct. It is a form of apophenia, which is the idea of observing a pattern in meaningless information or data. Leonardo da Vinci once said that pareidolia was a tool for painters to provoke viewers to interpret a simple set of colors and stains into something more, such as landscapes and complex expressions. Recently, a chicken nugget that resembled US President George Washington had earned more than $8,100 on eBay.

You might observe a resemblance of a face in the images below. The first one is an image taken in 1976 by the Viking Orbiter of a rock formation having somewhat of a resemblance to a human face. Newer and clearer images of the same Cydonia region in Mars show a simple set of lines that had previously been thought of as a human face. The second image is of a set of clouds that also show features that coincide with that of a face.

Dr. Nouchine Hadjikhani of Harvard University stated that humans are “prewired” to detect faces from birth, and that “If you take a baby just after a few minutes of life, he will direct his attention toward something that has the general features of a face versus something that has the same elements but in a random order.” Sophie Scott, a neuroscientist in University College London, also expressed that pareidolias can be a product of people’s expectations. People also strongly believe that pareidolias are a supernatural phenomena.

Whether they be pure coincidence or the work of a supernatural force, they are extremely interesting to observe and understand. Their use in artwork especially causes people to dig deeper than just the simple shapes and lines, allowing them to come up with their own depictions of the work.

pareidolia pareidolia3

The Ebbinghaus Illusion

July 25, 2014

The Ebbinghaus Illusion is a famous illusion in which the size of dots appears to be different due to the size of the objects around them.


The left hand dot seems to be smaller than the right hand dot, but they are, as is expected in a visual illusion, the same size.

This property of the brain, to adjust the size of objects in relation to their surroundings, can be a very useful one. When looking at a group of large objects, something that is relatively small should not be perceived as important. Contrastingly, when viewing a cluster of small objects, something relatively bigger should be viewed as more significant and important. Even if the relatively smaller and larger objects are the same, their surroundings decrease or increase their importance respectively. The orange dot on the left hand side is not as important as the same sized orange dot on the right hand side because one is enveloped by bigger dots while the other is surrounded by smaller dots. Perspective, once again, becomes the determining factor when viewing this image.

However, the size of the surrounding objects is only half the story. The distance between the central dot and the other dots is also a major factor in the perceived size difference. When the surrounding dots are farther away from the central dot, the orange dot will appear smaller because there is more space between it and the other dots. Contrarily, when the blue dots are close to the central, orange dot, the orange dot appears bigger. These two factors together make the Ebbinghaus Illusion very deceptive.

A determining neurological factor in the deceptive ability of this illusion to an individual is the size of their primary visual cortex, or V1, a region in the back of the brain that processes the visual information received from the eyes. The size of V1 is extremely variable from person to person. People can have a V1 three times the size of someone else’s. This leads to different perceptions of the Ebbinghaus illusion.

The Ebbinghaus Illusion correctly portrays the “flaw” in our visual system which leads to differential perceptive ability. Without this mechanism, we would focus just as much on the smaller objects in a large group of objects as the bigger ones. With this mechanism, we can effectively prioritize which objects need to be viewed in relation to others. Bigger objects in a group of small objects receive more attention while smaller objects in a group of big objects receive less attention.

Interestingly, children under 10, who have lower context-sensitivity (differential perception ability) and thus are not deceived by the Ebbinghaus Illusion. Don’t we all wish we could just be kids again!



Visual Illusions

July 25, 2014

Hello everyone!

I found a really interesting visual illusion that I would like to share.Screen shot 2014-07-25 at 1.52.34 PM


Above you can see two faces. Our brains are very used to perceiving faces and recognizing people. This illusion was created by psychologist Richard Russell from the University of Gettysburg. According to him, the left face is perceived as being a female face, while the right face is perceived as being a male face. Can you see it? The weird thing is that the two faces are actually identical! It is the same androgynous face. The only difference between the two faces is that the contrast between the eyes, lips and the rest of the face on the left is greater. The contrast on the left was increased while the contrast on the right was decreased. This creates the illusion that we are looking at a female on the left and a male on the right. This optical illusion demonstrates that impact of contrast on our vision is very important in perceiving the sex of a face. We unconsciously use contrast in order to differentiate between men and women!

I found this information very interesting. According to Russell, this optical illusion explains why cosmetics make women look more feminine. Lipsticks and eyeliners magnify the contrast between the eyes and lips and the rest of the face. The cosmetics industry is huge and it has developed because of this aspect of our visual system. Cosmetics exaggerate this contrast in order to make a female face appear more “feminine”. It is interesting that two identical faces with such a small difference as contrast can be perceived as so widely different by our brain. According to Russell, beauty is actually not skin-deep, it goes as far as the brain!


The Brain Structure of The Pale Orc

July 23, 2014

(This is a little late because of technical difficulties, but better now than never, right?)

For those of you that are familiar with the Lord of the Rings movies, you probably remember those ugly creatures called “Orcs.” And for anyone who’s seen The Hobbit, you’ll remember the giant orc leader named Azog, the “Pale Orc.” In general, orcs are roughly the size of humans, but Azog is a good three feet taller and much bulkier. Azog, like all orcs, is trained to be a predator. He has little to no empathy, a small range of emotions, and great fighting capability.

To jump right in, I’ll first talk about the size of Azog’s brain. Since he stands upright and shares a majority of physical human qualities, I believe that his brain would be the same shape as humans’, only much larger, due to his height and large skull.

While orcs do not have their own language, they speak a mixture of phrases and commands from different regions of Middle Earth. Thus, I believe that regions of the forebrain that ivolve language, along with his cerebral cortex, would be smaller in Azog than that of humans. Because while Azog can still communicate with other orcs, their communication is less developed than the average human.

Azog can kill without remorse, and never shows a shred of empathy in any scene. The only emotion one senses from him is anger and hatred. He has no motivation to be angry other than the fact that he was born to be a cold-blooded predator. Because of his very undeveloped emotional response, I believe that Azog’s prefrontal cortex would be very small, as it controls things like empathy, emotional control, and insight. Along with this, his frontal lobe as a whole would also be slightly smaller than humans’, because of his lack of emotions, reasoning, and problem solving (he needs some problem solving skills to be a leader of orcs, but nowhere near as much as humans develop problem solving.)

What traits does any predator need? Good sight, hearing, and smelling, of course. This leads me to believe that Azog has large olfactory bulbs for smelling, a large inferior colliculus for hearing, and a large occipital lobe for sight. With these three senses, Azog is able to track other species of Middle Earth when in battle.

Finally, Azog is trained to fight and kill, and he does it well. This leads me to believe that he would have a cerebellum larger than humans’, because he needs more motor control when in battle, which he is constantly involved in.


The Brain of Zazu from “The Lion King”

July 23, 2014



For this assignment, I chose Zazu, from the movie and musical “The Lion King”. Zazu is a Red-billed hornbill, a type of bird. The basic structure of his brain would be similar to those of other birds with a few differences.

I would think that Zazu’s encephalization quotient would be higher than the EQ of other birds, because his intelligence and level of brain function are much higher than other birds.

Most of the differences in Zazu’s brain would be found in the cerebrum. His cerebrum would be larger than the cerebrum of other birds. More specifically, the frontal and temporal lobes would be bigger. The frontal lobe control emotions, and since Zazu is able to process and display emotions, his frontal lobe would be large. Zazu is also competent with reasoning and problem solving, both of which the frontal lobe controls. The temporal lobe controls speech, and Zazu is a talking bird, so his temporal lobe would be larger than the temporal lobe of other birds. Zazu’s amygdala, in the temporal lobe, would also be more developed because it controls feelings of fear, and Zazu is often nervous and panics easily.

The cerebellum would also be more advanced than other birds, as it controls movement and he is able to move his wings in ways that normal birds can’t, such as crossing his arms.