Home Mind & Brain How Did You Not See That? The Case of Change Blindness

How Did You Not See That? The Case of Change Blindness

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I have recently had the opportunity to teach a topic of cognitive psychology that I was unfamiliar with as my own research has not directly investigated this phenomenon. I had been taught some details throughout my university education, but as the area was not part of my own research in memory, I had not been able to take the time to look at the area in more detail. As I eventually aimed support students with their own independent learning alongside my colleagues, I had to make sure that I had a good understanding of the area myself. I decided to embark upon the very long (but interesting) task of developing my own independent research and reading skills within the area that I would be discussing with students.

The chosen topic area for the class I was working in, was a phenomenon known as ‘change blindness’ and it is one area of psychology that is slightly under-researched, in particular in relation to more recent years. Change blindness refers to when people fail to detect relatively large changes in visual scenes. For example, it has been shown that people can miss large animals being present in some parts of visual scene, such as a gorilla, and it has also been shown that even changes of faces can be difficult to detect within scenes. Usually, change blindness does not solely occur due to one reason. It could be present due to brain injury in some cases, or even eye or visual problems, but it can also occur if people simply find it difficult to take in all of the information within a scene in one go. 

While reading around the area, I found it quite interesting that there are many factors which can influence a person’s ability to view and perceive a full visual scene, so that means everything in their own visual field that they are currently looking at. When people are trying to look at a face within a visual scene, this can have an advantage over a non-face or object, and people are more easily able to see when someone’s face has changed in comparison to a change of something that is not related to a face. When an object is changed in a scene, however, the difference in a person’s view is quite distinct and a person may find it really hard to figure out that the original object is no longer there. Within psychology, there are two types of experiments which can be used to look at change blindness and one of the main experiments is called a flicker paradigm. In this paradigm, people are shown a still visual scene which shows alternating images of the same scene, some with changes and some without. It is then up to a person to decide if there has been a change and a person’s reaction time is often recorded so that we can see how long it has taken them to find if there has been a change or not.

Studies, which I have read, have clearly suggested that people can detect a change of a face quicker than an object as people are more often around faces in real life than individual objects such as appliances or clothes. One reason for faces having an advantage over objects is that faces have meanings to them and it has been suggested that people can process faces in a different way to objects. Meanings of faces can convey emotions such as anger or happiness – expressions which a person would associate with different types of visual scenes.

Let’s take this example here: If you were looking at a scene of a group of children playing in a park on a hot summer day, with one child looking angry or unhappy in comparison to everyone else. A person looking at the scene would automatically recognise this and would start to think about why the child was unhappy. Did they have a bad day? Has someone spoken to them in an unpleasant way? If this angry child then changes to a happy child, this again would be easily recognised as the expression of that child’s face would have a meaning in relation to the scene. The child could simply be involved with the happy games being played by the children or they could be enjoying the sunshine, hence the happy expression on their face. Often, it’s not just the visual details of a scene that people take notice of as it can also be the semantic information. When I talk about semantic information, I simply mean the information that can provide meanings to the visual information seen by a person, such as knowing that a smiling face can mostly mean that a person is happy.

I also found out that the amount of detail, in the scene being viewed, can impact the amount of information a person can remember and it can also influence a person’s ability to decide if something has changed. If a person is viewing a scene which contains many different people, objects and background details then this can cause a person to miss some of the details which could be important in the scene. If an item is placed in the background of a scene in comparison to the foreground then this again can cause a person to miss a change, as people tend to pay attention to the things that are closest to them. For those of you who would like to read more about the theory behind the amount of information in a scene, please look at The perceptual load theory from Professor Nilli Lavie who has conducted extensive research on reasons why people can only pay attention to certain things.

So, is there any way in which we can stop people from missing important details in a scene or not realising when something has changed? The simple answer is no. The only thing we can do, as researchers, is investigate why people can miss important details in a scene. There are many ways in which this can be done, but one direction of interest to me is to look at the brain areas which could be related to visual scenes. Areas in the brain can be related to movement and visual images, and asking people to take part in experiments which show them irrelevant details can provide an insight into how the brain reacts in complex and simple visual situations. This will hopefully help us to understand change blindness in more detail in future years to come.

Laura Jenkins, PhD is a teaching associate in the School of Sport, Exercise and Health Sciences at Loughborough University. 


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