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It is a natural assumption we all make, that when our eyes are open, we are ‘seeing’ everything in our visual field. However this is not often the case.

Before you continue reading, watch the following video and count how many times the players dressed in white pass the ball to each other.

The correct answer is that they pass the ball to each other 15 times, but the real question is, did you see the gorilla? If the answer is no… go back and watch the video again but this time without focusing on the number of passes the players make. But don’t worry if you didn’t spot him the first time! This video is based an experiment performed by Daniel Simons and Christopher Chabris in 1999 and they found that amazingly 50% of their participants failed to notice the gorilla. So what is it that causes us to miss such a supposedly obvious feature of the video?

Selective Attention

Attention is the process by which people select certain information from their surrounding environment, and focus in on only that, thereby discarding the rest of the sensory input. This is because we have a limited cognitive capacity, and so have to filter out what we assume to be irrelevant, or else we would be subject to a sensory over load. This is as Broadbent (1958) described it, like the brains way of filtering incoming information. This means that at any given time we are only attending to a select area of our visual field, and often miss large changes in the areas of the environment we are not focusing on. (You now have an excuse when you don’t realise you friend got a new hair cut..!).

Inattentional Blindness

Inattentional blindness is an extension of selective attention, and it claims that without attention no features from our surroundings are perceived at all. Mack and Rock (1998) were among the first psychologists to study this phenomenon, and they argued that it occurred when the participants in their experiments were attending to a specific stimulus, and so were unaware of others presented to them. This suggests that missing an external stimulus in your visual field is no reflection on a deficit in your perceptual abilities, but in your ability to attain. Therefore we concentrate mostly on what we find important, and then simply allow our schemas to fill in the rest.

How can we test this phenomenon?

Mack and Rock Task

Mack and Rock would show their participants a series of crosses, aligned either horizontally or vertically, and they were asked to determine which arm of the cross was longer. On the critical trial, the cross shows up like all the previous trials, but it is accompanied by a small shape. Afterwards the subjects were  asked if they noticed any shapes other than the cross, and the results showed that  75% of the participants were inattentionally blind when the cross was given parafoveally, and the unexpected shape appeared at the fixation point. In addition to this, they also allowed for an assessment of perception under divided attention, by repeating the experiment, but suggesting to the participants that something other than the cross might appear. This showed that when the subjects were aware that something would change (they attended more to the external environment), they were far more likely to notice the additional shape.

An explanation for Inattentional Blindness

A salient object is one that stands out from the rest, and so because our brain doesn’t have the cognitive capacity to process and retain every stimulus from our environment, we rely on our schemes to fill in the rest, and focus only on those which are salient. A schema in this sense is effectively a mental arrangement of preconceived ideas that develops throughout ones life. This is a very economical approach to perception, as attending to, and cognitively processing only the important aspects of our environment doesn’t over load our cognitive capacity, but does allows us to create a fairly cohesive idea about the world around us.

But why do we miss such as obvious environmental stimulus, that is the presence of a man dressed as a gorilla?! This answer to this could be due to the fact that it is such an unexpected event, that it completely lacks ecological validity. Therefore because we aren’t expecting it, we are less likely to notice it, as we are attending only to the most salient stimuli.

Whodunnit?!

The following video is taken from a British TV advert, promoting increased attention when driving, and nicely demonstrates our inability to notice changes in our visual field that we are not attending to.

So remember: 

In popular culture and media, the idea of hemispheric dominance has created a misunderstanding of brain function. One of the most popular misconceptions is the idea that hemispheric dominance is connected to personality type. This idea entirely oversimplifies the idea of the lateralization of brain function. In the widespread pop-culture version of hemispheric dominance, certain personality traits are assigned specifically to one side of the brain. Left-brained people are assumed to be logical, analytic, strategic, and practical. Right-brained people are understood to be passionate, creative, intuitive, and emotional. This idea is so infiltrated into popular belief that one search of “hemispheric dominance” yield pages and pages of results for left brain vs. right brain dominance tests. The amount of these tests indicate how many people are using these to evaluate their own way of thinking and behavior on a measure that has no scientific truth behind it.  It is essential that people understand the neuroscience behind brain function in order to debunk the myth behind the lateralization of brain function.

In order to analyze the concept of hemispheric dominance it is imperative to understand the history of split-brain experiments. In the early 1960’s Roger Sperry worked extensively with a severely epileptic patient that had his corpus collosum split. Sperry discovered that certain activities could only be accomplished when using one side of the brain, thus the concept of laterality. Laterality means the dominance of one side of the brain in controlling particular activities or functions.

Sperry’s experiment led to a whole new branch of research aimed towards laterality and hemispheric dominance. Previous research has shown that language processing for 95% of people is mostly located in the left hemisphere in the form of Broca’s and Wernicke’s areas. The right hemisphere has proven to be responsible for spatial awareness along with memory, attention, and problem solving. Another intricacy involved with hemispheric dominance is contralateral control of motor control, vision, and language.

Sperry’s research best describes contralateral cognitive processes. Images were flashed in front of subjects with severed corpus collosa. When an image was flashed in the subject’s right visual field (RVF) the image was being processed in the left hemisphere. Since language processes are generally based in the left hemisphere, the subject could verbally recall the object flashed in front of them. However, since motor control is usually based in the right hemisphere, the subject could not draw the object when prompted. When an image was flashed in front of the subject’s left visual field then the right hemisphere processed it. The contralateral processing resulted in an inability to verbally recall the object but the ability to draw the object remained in tact. Although there are well-documented instances of lateralization, there are also cognitive abilities that are ipsilateral. The most common example is olfactory processing.

Whilst it is true that each hemisphere of the brain has certain functional specializations, the substandard understanding of the existence of lateralization has lead pop psychological articles to depict the brain as being divided into two separate parts, almost independent of each other. This is a myth.

Pseudo-psychology often suggests that individuals are either ‘right-brained’ or ‘left-brained’ depending on their personality type, and often determine this from their jobs and personal life. For example, pop psychologists might be inclined to tell a musician that he is a ‘right brained’, whist telling a math teacher he is ‘left brained’. This is a massively over simplified understanding of how the two sides of the brain interact. For example linguistic functioning is associated with just the left side of the brain, but in reality the right side contributes a huge amount. Recent studies have indicated that individuals with damage to their right hemisphere often have trouble with semantics, and a reduced ability for metaphor appreciation, both vital aspects of language comprehension.

In reality it appears that most basic cognitive processes utilize both sides of the brain, and the idea that an individual can being either left or right sided, is a huge exaggeration. The two hemispheres are massively interconnected by the corpus callosum as well as other bands of nerve fibers, which connect both sides of the brain. These allow many of the brain processes to span across both sides, and create a more holistic idea of consciousness.