Inattentional blindness: What captures your attention?

ISMP error alert


A pharmacist enters a prescription for daily methotrexate into the pharmacy computer. A dose warning appears on the screen. The pharmacist reads the warning, bypasses it, and dispenses the medication as entered. The patient receives an overdose of the medication and dies.

This error, and many others, happen because the person performing the task fails to see what should have been plainly visible; later, the person cannot explain the lapse.1 People involved in these errors have been labeled careless and negligent, but these types of accidents are common, even in intelligent, vigilant, and attentive people. The cause is usually rooted in inattentional blindness.1

Processing information

Most mental processing occurs outside of conscious awareness. The amount of information that can be taken in by our senses is limitless. But the brain has very limited resources when it comes to attentiveness. To combat information overload, the brain allows large amounts of information through almost entirely unassimilated, peeling off just a few pieces of selected information for a closer look.2

Accidents happen when one’s attention mistakenly filters away important information and the brain fills in the gaps with what has been aptly referred to as a “grand illusion.”2 In the example above, the brain of the pharmacist filtered out important information on the computer screen and filled in the gaps with erroneous information that led him to believe he had read the warning appropriately.

Mental workload and task interference

Inattentional blindness is more likely to occur if part of your attention is diverted to secondary tasks, such as answering the phone while entering prescriptions into the computer or even thinking about dinner plans while transcribing an order.

Low workload causes boredom and reduces the mental attention given to tasks, as does carrying out highly practiced tasks, such as counting out medications. We spend a large majority of our waking life functioning with the equivalent of an automatic pilot, with occasional conscious checks to ensure that tasks are carried out properly. This makes us particularly prone to inattentional blindness.


Expectation has a powerful effect on our ability to pay attention and notice information. Our past experiences also teach us what is relevant. Errors occur when new or unusual circumstances happen in highly familiar situations.

The pharmacist who did not notice important information on a computer warning had rarely encountered a clinically significant computer alert and had subconsciously learned that there was nothing important to see when reading alerts. Nothing had ever happened, so attention was automatically filtered away from the details to conserve mental processing.


The capacity to pay attention is variable and influenced by age and mental aptitude. In addition, attention is variable within an individual because of distractions, alcohol, drugs, and fatigue.


A pharmacy technician working in a stockroom reported a product packaging problem that she thought was a medication error waiting to happen. The products involved are polymyxin B, trimethoprim ophthalmic solution; and neomycin, polymyxin B, and gramicidin ophthalmic solution (Figure 1), both manufactured by Bausch & Lomb. Conspicuity is the degree to which an object or piece of information “jumps out” and captures your attention. The best way to achieve this effect is through use of contrast, color, or shape to call attention to differences in packaging. The packaging of these two products has none of these features.

Confirmation bias can occur when packaging is similar and we think we have the correct product in our hand. In that case, the brain may “ignore” information that would disagree with what we believe we see on the label. The brain processes words as a whole, not by the individual letters. This can lead to misreading of labels when the print is similar.

Error prevention

It is difficult to reduce the risk of inattentional blindness, as it is an involuntary and unnoticed consequence of our adaptive ability to defend against information overload. Error-reduction strategies such as education, training, and rules are of little value. Instead, efforts should center on increasing conspicuity of critical information and decreasing diversions of attention and secondary tasks when carrying out complex tasks.


  1. Green M. “Inattentional blindness” and conspicuity. Visual Expert. Accessed at, March 1, 2012.
  2. Angier N. Blind to change, even as it stares us in the face. New York Times. April 1, 2008. Accessed at, March 1, 2012.