Inattentional Blindness in Psychology

Take-home Messages

  • Inattentional blindness (also called perceptual blindness) is the failure to notice something that is completely visible because of a lack of attention.
  • The phenomenon of inattentional blindness seems to have been discovered in the 1970s; however, it was first introduced as a concept in 1992 by Irvin Rock and Arien Mack.
  • A want of either sensory conspicuity or cognitive conspicuity, a lower working memory capacity, and a higher mental workload may cause inattentional blindness.
  • Consequences of inattentional blindness in the real world may include automobile collisions, aircraft accidents, and material threats to the safety of police officers during vehicle stops.

What Is Inattentional Blindness?

Inattentional blindness occurs when one fails to notice a readily visible yet unexpected visual stimulus in one’s sight (Simons & Chabris, 1999).

This temporary unawareness is likely to stem from an abundance of visual stimuli meriting one’s notice.

In such a scenario, one may fail to perceive even salient yet unanticipated objects.

The criteria below are essential to identify an occurrence of inattentional blindness (Rock, Linnet, Grant & Mack, 1992):

  1. The observer fails to recognize a visual event or object.
  2. The optic stimulus is fully visible.
  3. The stimulus would be readily identifiable if the observer consciously noticed it.
  4. The stimulus is unanticipated, and the failure to recognize it stems from a collapse of attention and not from any drawbacks of the visual scene or the optic stimulus.

It is important to note that inattentional blindness is distinct from other drawbacks of visual recognition, such as attentional blinking, repetition blindness, visual masking, and change blindness (Driver, 1998).

What fundamentally distinguishes inattentional blindness from the aforementioned phenomena is the unforeseen character of the optic stimulus, which escapes the observer’s attention.

The earliest discovery of the phenomenon seemed to have been made by the father of cognitive psychology, Ulric Neisser, and his fellow researchers during the 1970s (Neisser, 1979; Neisser & Becklen, 1975).

In a research study they conducted, the participants watched two superimposed yet distinct videos of individuals engaged in various activities (e.g., throwing a basketball or hand slapping).

When the participants fixated their attention on one event, an unexpected occurrence in the other event was more likely to evade their notice.

Despite these discoveries, however, it was much later, in 1992, that ‘inattentional blindness’ was introduced as a psychological concept by Irvin Rock and Arien Mack (Rock, Linnet, Grant & Mack, 1992; Mack & Rock, 1998). Their book titled “Inattentional Blindness” sought to detail the phenomenon by employing various procedures.


The following are some instances of inattentional blindness from everyday life.

  • While watching a movie supposedly depicting a scene from ancient Israel, you fail to spot a blooper, an anachronistic jet flying in the background.
  • You drive while carrying a conversation on the cell phone. You fail to pay attention to a cab swerving into your lane and end up having a collision.
  • You are mentally working on a math problem while walking on the sidewalk. You fail to notice a ditch in front of you and end up falling into it.

Research Findings

Probably the most famous study on inattentional blindness, also known as the “Invisible Gorilla Test,” was carried out by Daniel Simons and Christopher Chabris (Simons & Chabris, 1999).

In this study, participants watched a video of people dressed in black and white passing basketballs. Participants were asked to count the number of times the team in white passed the ball. During the video, a person dressed in a black gorilla costume walks between the two teams.

Subsequently, the participants were asked whether they had seen anything unusual in the video. Nearly half of the participants provided negative responses.

Despite its evident salience, the sight of the gorilla had evaded the attention of many of the observers who were focused on the demanding task of tracking throws and passes.

Because participants were so focused on the number of times the white team was passing the ball, they completely tuned out other visual information

In a similar experiment, researchers tested inattentional blindness by asking participants to observe images moving across a computer screen.

They were instructed to focus on either white or black objects, disregarding the other color. When a red cross passed across the screen, about one-third of participants did not notice it (Most, Simons, Scholl, & Chabris, 2000).

inattentional blindness experiment

Figure 1. Nearly one-third of participants in a study did not notice that a red cross passed on the screen because their attention was focused on the black or white figures. (credit: Cory Zanker)

The cross remained on the screen for 5 seconds and was readily distinguishable from the black and white objects on account of both shape and color (see Fig. 1)

The outcome of the experiment seemed to suggest that people’s awareness might be attuned to distinct perceptual dimensions and that unforeseen stimuli resembling the environment are more likely to induce inattentional blindness.

Moreover, a study that investigated the impact of divided attention while walking unveiled notable findings (Hyman, Boss, Wise, McKenzie & Caggiano, 2009). The participants of the experiment were categorized based on whether they were listening to an MP3 player, talking on a phone, being accompanied by another person, or merely walking without any electronics.

The unusual visual stimulus for the experiment was a unicycling clown garbed in vivid attire. The results indicated that the participants engaged in phone conversations were the least likely to recognize the clown on the unicycle.

The outcome seemed to suggest that the use of cell phones may induce inattentional blindness even in elementary tasks like walking.

Why It Occurs

Because our attentional and processing resources are limited, our brain dedicates them to what fits into our schemas, or our cognitive representations of the world (Cherry, 2020).

Thus, when an unexpected stimulus comes into our line of sight, we might not be able to process it on the conscious level. The following explanations illustrate how this might happen.


Conspicuity holds that certain sensory stimuli (such as bright colors) and cognitive stimuli (such as something familiar) are more likely to be processed, and so stimuli that don’t fit into one of these two categories might be missed (Mack, 2003).

One of the reasons why people so often “miss the gorilla” is because the sight of a gorilla in a basketball match constitutes a rare occurrence in the real world. Consequently, while occupied in the cognitively demanding work of observing certain details of the game, one might fail to perceive such unusual visual stimuli.

The conspicuity of a visual stimulus stems from its physical attributes, which determine its level of salience. In contrast, its cognitive conspicuity stems from its familiar associations with the observer’s autobiographical history (Mack, 2003).

When a stimulus’s sensory conspicuity or cognitive conspicuity drastically lessens, inattentional blindness is likely to ensue. For instance, when an object is visible yet not visually prominent, it may likely evade notice. On the other hand, even a visually striking object may fail to capture an observer’s attention if it is irrelevant to the observer’s interests.

Mental Workload

The mental workload theory describes how when we focus a lot of our brain’s mental energy on one stimulus, we are using up our cognitive resources and won’t be able to simultaneously process another stimulus (Mack, 2003).

Similarly, some psychologists explain how we attend to different stimuli with varying levels of attentional capacity, which might affect our ability to process multiple stimuli simultaneously.

For instance, when an individual focuses highly on a particular stimulus (e.g., the content of a cell phone conversation while driving), less attention is bestowed upon other stimuli (e.g., the other cars on the road).

Consequently, in such a situation, the individual may fail to observe an unforeseen yet salient occurrence (e.g., a deer in front of the individual’s car).

Alternatively, however, when the mental workload is small, one is more likely to become cognizant of the appearance of unanticipated stimuli.

Working Memory

Although the evidence is inconclusive, some research findings suggest that those with a lower working memory capacity are more susceptible to inattentional blindness.

An example is a study that investigated whether variability in working memory capacity (which reflects attentional control) influences susceptibility to inattentional blindness (Seegmiller, Watson & Strayer, 2011).

The experiment utilized the same video of the gorilla in Simons’ and Chabris’ study. Additionally, however, the participants participated in a mathematics examination that would gauge their working memory capacity.

The results indicated that those with a lower capacity were less likely (36%) than those with a higher capacity (67%) to notice the gorilla. The outcome implies that variability in attentional control is a possible mechanism undergirding the seeming modulation of inattentional blindness across various individuals.


While the results of inattentional blindness in research experiments may sound benign or even humorous, its implications in real-life can be tragically devastating.


Research shows that focusing on a particular object may result in inattentional blindness (Simons, 2000). This means when an individual is texting or carrying a conversation while driving, his or her primary focus may be veered off the roadway.

This may result in a failure to notice objects on the road, such as stop signs, speed limit indicators, or even other cars. Inattentional blindness herein can result in accidents and potentially even death.


A heads-up display (HUD) utilized in aviation too, may induce inattentional blindness (Green 2002).

HUD projects information onto a helmet-mounted screen or the windshield while simultaneously enabling pilots to keep looking ahead through the windshield.

Simulator studies have shown, however, that HUD may lead to incursion accidents on the runway. Given the increasing prevalence of HUD in tanks and automobiles, the discovery has serious implications even outside aviation.

Law Enforcement

A study that investigated inattentional blindness among the police shows that even experienced officers might fail to notice a firearm positioned in plain sight inside a stopped vehicle (e.g., such as on the dashboard) (Simons & Schlosser, 2015).

Even though they are trained to recognize dangers in their environment, in the study, the officers did not notice the gun, regardless of whether the driver’s style of interaction was aggressive or cooperative.

This type of inattentional blindness can endanger the safety of police officers encountering potentially hostile drivers.


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Simons, D. J., & Chabris, C. F. (1999). Gorillas in our midst: Sustained inattentional blindness for dynamic events.  perception 28 (9), 1059-1074.

Saul Mcleod, PhD

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Educator, Researcher

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.

Ayesh Perera


B.A, MTS, Harvard University

Ayesh Perera has worked as a researcher of psychology and neuroscience for Dr. Kevin Majeres at Harvard Medical School.