Would you notice if someone in a gorilla outfit walked in front of you? Probably. But what if the gorilla walked in front of you while you were distracted and focusing on something else? You might not notice that gorilla.
Psychological research on inattentional blindness tries to understand why we do not remember everything we see. Psychologists generally assume that we must pay attention to what we see for it to enter our long-term memory.
- First, we are going to review the inattentional blindness definition
- Next, we will look at other psychological concepts similar to inattentional blindness, such as change blindness.
- Then, we will look at an inattentional blindness example highlighted in psychology research.
- Finally, we will review why inattentional blindness is an important concept.
Inattentional Blindness Definition
Inattentional blindness is when someone fails to notice a stimulus because they are not fully paying attention. The person does not realise that something is in their field of view.
An example of inattentional blindness is looking at a map while driving and not noticing an animal ahead.
This psychological principle explains why texting and driving is such a bad thing! When you are texting and paying attention to your phone, even if you think you still have some focus on the road, you become inattentional blind to your surroundings. Inattentional blindness is why people swerve, come to screeching halts, or hit pedestrians when they are on their phones.
Fig. 1. People are not as good at distracted driving as they think.
Inattentional blindness can also take place outside of driving. Any time there is a stimulus or object you do not notice because you are focusing on something else, you fall prey to inattentional blindness.
You could be doing homework and not realise that your cat is sitting in the chair across from you or at a sports practice; if you're focused, you may fail to realise that people have come to watch.
Change Blindness vs Inattentional Blindness
One similar concept to inattentional blindness is change blindness. Inattentional blindness says that you will not realise that an object exists because you're focusing on something else that made you blind to that stimulus.
Change blindness happens when someone does not notice a visual change in their surroundings.
Change blindness would say that because you are focused on texting and not driving, you may not notice a tree getting bigger as you move closer to it.
Inattentional blindness says that you would not notice a stimulus appearing, while change blindness says that you would not notice a stimulus changing. That's the difference!
In a study by Simons and Levin (1998), an experimenter started a conversation with a pedestrian. Halfway through the conversation, some workers intervened, and a confederate swapped places with the original experimenter. Interestingly, only half of the participants noticed this switch.
Inattentional Blindness Example
Now that we've looked at the difference between inattentional blindness and change blindness, let's look at other concepts similar to inattentional blindness.
One phenomenon similar to inattentional blindness is unilateral hemispatial neglect. This typically affects one hemisphere of the brain and causes the person not to perceive things in the visual field opposite the damaged area.
The brain has a contralateral relationship, meaning that the right hemisphere processes things we see in the left visual field and vice versa. Unilateral hemispatial neglect is a neurological symptom of physical trauma to the brain or a symptom following a stroke.
If someone has a stroke and the left side of their brain is damaged, they might not perceive stimuli in their right field of vision.
Attention blink is another concept that affects our visual perception. Attention blink happens when two stimuli are shown in rapid succession. If the stimuli are shown so close together, such as 200 milliseconds, our brain will fail to process the second stimulus.
Repetition blindness is similar to attention blink in that stimuli are shown very quickly. However, repetition blindness says that the more a stimulus is repeated, the less likely you notice it.
If you watch numbers flash on a screen in the order of 1-4-6-3-4-8-7-0, repetition blindness would say you are less likely to see the second 4 than the 8, 7, or 0.
Inattentional Blindness Experiments
Now let's look at one of the most famous inattentional blindness experiments conducted by Daniel Simons and Christopher Chabris.
Their research aimed to complement Moray's (1959) research. Moray's research focused on understanding auditory attention and the factors that can impact our auditory attention. Simons and Chabris, on the other hand, investigated visual attention.
The research goal was to measure the extent of inattentional blindness under different conditions when watching dynamic video clips. The research explains why we do not always remember the things we see.
Inattentional Blindness: Research Design
The sample included 228 participants, predominantly undergraduate students, who volunteered to participate in the experiment. The design was a lab experiment that used independent measures design. The independent variables were:
- White versus black condition– two basketball teams, were shown. Participants had to either observe the team wearing white or black.
- Easy versus hard Task condition– participants had to count either the number of passes made between the team in their head (easy) or the number of bounce passes and aerial passes made between the team in their head (hard).
The team they were asked to count the team determined in the level 1 condition.
- Umbrella woman condition versus gorilla condition– a tall woman with an open umbrella entered the playing field, or a shorter woman in a gorilla costume entered the playing field. In each condition, they were shown for 5 seconds.
Two types of video clips were shown: transparent and opaque. In the opaque condition, the unexpected clip was shown clearly, while in the transparent condition, the visibility of the unexpected event was less clear. The two levels of the IV participants were tested on were:
- White easy/white hard/black easy/black hard.
- Opaque umbrella woman/transparent umbrella woman/opaque gorilla/transparent gorilla.
The dependent variable was the number of participants (in %) who noticed the unexpected event (the 'umbrella woman’/gorilla).
First, researchers obtained informed consent from participants. Participants received standardised instructions. The researchers read them to the participants to ensure everyone receives the same instructions.
This reduces external factors affecting the validity of the results and ensures the study is replicable and consistent (which may infer internal reliability).
Fig. 2. Would you notice someone walking through in a gorilla costume?
Then, participants were shown four video clips in which three people from each team played basketball. The unexpected event occurred halfway through the video clips (the woman with the umbrella or the woman in the gorilla costume).
After the video clips, participants had to write down how many passes they counted and fill out a questionnaire. If, at any point, participants indicated they had noticed the unexpected event, the remaining questions were skipped.
The questionnaire included the following questions:
- Did you notice anything unusual on the video while counting?
- Did you notice anything else besides the six players?
- Did you see anyone else appear on the video besides the six players?
- Did you see a gorilla (a woman with an umbrella) walking across the screen?
Inattentional Blindness Experiment Results
Some participants had to be excluded, so the remaining data was from 192 participants. 54% noticed the unexpected event, and 46% did not.
More participants noticed it in the opaque condition (67%) than in transparent (42%).
More participants noticed the event in the mild condition (64%) than in the severe condition (45%).
More noticed the umbrella woman (65%) than the gorilla (44%).
The table shows the percentages of participants who noticed the umbrella woman/gorilla in the white/black conditions.
| Gorilla | Umbrella-woman |
| White team | 27% | 69% |
| Black team | 58% | 62% |
There was hardly any difference between the white and the black condition when the umbrella woman was shown in the video clip.
The researchers concluded that the results confirm people are inattentive when observing dynamic events. They also found that task difficulty influences the extent of inattentional blindness.
The results demonstrate that people perceive things more with similar basic characteristics (in this study, colour). The gorilla was black, and participants perceived it more when they observed the black team.
The results contradict the traditional view that people perceive things that stand out in visual search tasks.
Inattentional Blindness in Psychology
The study by Simons and Chabris (1999) added to previous research on attention. The study advanced psychological research by identifying the factors involved in inattentional blindness. This has practical applications in real life, such as showing the importance of focusing on a specific task.
In terms of driving, the study shows that the following factors can cause/influence inattentional blindness:
- Poor visibility, e.g., in bad weather.
- Physical features, such as other cars, can be perceived, while animals cannot.
- If you are doing a difficult task while driving.
In psychology, inattentional blindness is important because it explains that we cannot focus as well as we think. People who text and drive think it's fine because they can pay attention to their phones while driving.
Simons and Chabris' research, and all other research built upon this, shows the existence of inattentional blindness. This concept, coupled with the other types of selective attention and blindnesses, teaches us just how blind we can be, even when we think we are paying attention.
Inattentional Blindness - Key takeaways
- Inattentional blindness is when someone fails to perceive a stimulus that is obviously present because they are not paying attention.
- Change blindness happens when someone does not notice a change in their visual field.
- Unilateral hemispatial neglect happens when someone with damage in one brain hemisphere leads to the individual no longer being able to attend to stimuli on the opposite side of vision.
- The intentional blindness experiments conducted by Simon and Chabris (1999) measured the extent of inattentional blindness under different conditions when viewing dynamic video clips.
- The results showed people are inattentive when watching dynamic events.
Explanations 
Textbooks 
Exams 
Magazine 
