6.3 Change Blindness: Definition & Examples

Jan 13, 2020 | Cognitive Psychology, Courses, ch6 Attentional Processes & Theories

Change blindness is a fascinating phenomenon that most people experience throughout their lives. Through this lesson, you will learn how to define change blindness and explore some of the ways that it operates in the real world.

What Is Change Blindness?

Have you ever been so engrossed in a conversation at a party that you failed to notice that someone new is standing only six inches away from you, trying to get your attention? It’s possible that you were so distracted that you didn’t notice someone approaching you. But it’s also entirely likely that you were experiencing change blindness.

Change blindness is a phenomenon that occurs when a person is unable to notice visual changes in their environment, despite the fact that they are often rather obvious. In cases of change blindness, the person isn’t failing to notice small or insignificant changes, but will probably miss big changes, like someone standing next to them waving their hand.


Early experiments with change blindness focused largely on memory and perception when viewing pictures. For example, a person might be shown a photograph of a street scene in Egypt and told to memorize the image. Following that, they would be shown the same picture with certain elements added or taken away and asked to identify what’s different. Very often the individual could recall the larger aspects of the picture but couldn’t recognize the smaller changes.

An inability to recognize every change in a crowded or complicated picture is generally attributed to the brain’s capacity to remember complex images in a broad scope. For example, they might remember looking at a picture of a crowded street with stores and restaurants, but they probably wouldn’t notice that the names of the stores had changed. In general, this is because the brain cannot possibly process every element of an experience and has to prioritize what it believes to be important.

Inattentional Blindness

In the 1990s, researcher Daniel Simons conducted a fascinating study into change blindness that many people find unbelievable. In Simons’ study, he asked participants to watch a video of a basketball being passed around between several people, with a particular focus on the basketball itself. When the experiment was over, Simons found that a large number of participants were so focused on watching the basketball being passed around that they failed to notice a man in a gorilla suit jumping around in front of the camera.

It’s important to note that the change in Simons’ video wasn’t subtle. The gorilla is very obviously taking up much of the frame. Simons concluded that participants were experiencing inattentional blindness, which is when a person fails to notice a major change because they are so focused on another task. In this case, because participants were asked to focus on the movement of the basketball, their brains prioritized that task in order to do it properly, thereby missing the other things happening in the video.

In the case of Simons’ study, participants engaged what’s referred to as attentional selection, which is when a person selects certain things to focus on in order to achieve a task and filters out anything that is unrelated to the objective.


There are a number of theories about what causes a person’s inability to recognize obvious changes in their environment, but most agree that the phenomenon is related to sensory processing. Broadly speaking, our brains have a limited capacity to detect and process everything in our environment. Instead, what the brain does is choose certain things to process, evaluate, and store, which allows other things to be missed or filtered out.

In simple terms, change blindness has a great deal to do with where a person directs their attention. In the case of the gorilla and the basketball, people focused their attention almost exclusively on one thing, which caused them to miss other elements or changes. Given that attention is often at the root of change blindness, a person’s age or mental and physical health can influence how well they will notice changes in stimuli.

Another important factor is object presentation, which is how objects or other visual stimuli are presented or introduced. For example, in experiments involving identifying changes in pictures, the brain can detect some of the major changes because they are obvious, but they might miss smaller ones that are hidden throughout the image. Moreover, a person is more likely to notice something being added to an image than something being taken away. Researchers believe that this is because adding something to an image forces the brain to reconsider the picture and the object’s relationships with one another.

Importance of Change Blindness

Given that change blindness is largely related to our cognitive limitations, it is unlikely that there will ever be a cure. Nevertheless, research remains important in order to mitigate the potentially dangerous outcomes.

Take, for example, a bus driver that drives the same route every day. They may be so focused on the road in front of them that they fail to notice that a small child has walked into the street fifteen feet ahead. The same can be said for piloting an airliner or any other activity that requires a person to be aware of their total surroundings.

Change blindness can have important implications for courtroom testimony as well. Imagine that a person testifies that they saw someone rob a bank and that the person was alone in committing the act. It is possible that because they were so focused on watching one individual, they missed the other two robbers who entered the bank shortly afterwards and assisted in the robbery.

Lesson Summary

Change blindness is a phenomenon in which a person fails to recognize changes to their environment or visual stimuli, despite their being very obvious. This can be seen in Daniel Simons’ research in the 1990s, in which people missed the introduction of a gorilla into a basketball game due to what he calls inattentional blindness.

In many cases, this is caused by neurological limitations, but it also might be the result of attentional selection, which is when a person chooses a certain number of things to focus on, while other things are filtered out. Moreover, it is possible that things like age and health can be a factor, or something more subtle like object presentation.

6.4 Attentional Blink: Definition & Experiment
6.2 How Divided Attention Affects Multitasking