Quick – think of the location of the nearest fire extinguisher to where you work (your office, desk, station, or whatever). Fire extinguishers are fairly large and usually conspicuously red objects that are deliberately placed in an obvious and accessible location. Their design and placement is meant to make you notice them, so that you know where they are in an emergency.

However, in a recent study, only 13 out of 54 subjects (24%) we able to recall the location of the nearest fire extinguisher to their office. In some cases subjects worked in the same location for years and walked by the fire extinguisher multiple times per day. How could they not notice something so obvious after hundreds of encounters?

Psychologists have identified a number of phenomena related to how people attend to the world around them. By now you have probably seen the famous basketball passing video (if not, take a look before reading further). This is an example of inattentional blindness – we can only attend to a small percentage of all the sensory information that is coming our way. Our brains evolved to sift through this information and pick out the bits that are likely to be important or relevant. Further, we can consciously direct our attention at certain details of the environment, and when we do we become relatively blind to other aspects of our environment to which we are not attending.

We are also subject to change blindness – even major changes that occur right before our eyes can be missed. This appears to be due to attention and visual processing. Change blindness is less for foreground objects than background objects, for approaching objects than for receding objects, and for new objects in our visual field than for existing objects. These all suggest that we are more likely to detect change for  those things in our visual field that also tend to have a stronger grip on our attention.

The new study possibly identifies a third distinct phenomenon known as inattentional amnesia. It is likely that the subjects in the study noticed the fire extinguisher at some point over the years (probably many times) but for some reason they still did not remember it. This implies that memory for such details is not automatic for most people, even through extreme repetition. There has to either be a trigger or a conscious effort to remember the detail.

There are many examples of this from everyday life. Try to recall the details of a common object. lan Castel, an associate professor of psychology at UCLA and lead author of the study, notes:

“If I asked you to draw the front of a dime or the front of a dollar bill from memory, how well could you do that? You might get some elements right. Do you know who the president is? On the dime, is he facing left or right? Does it say ‘In God We Trust’ on the front of the dollar or the back? Do you know what else it says? You’ve seen it so many times, but you probably haven’t paid much attention to it.”

We tend to notice and remember details that are important to us. Chess masters are better at remembering the location of pieces on a chess board. Physicists are better at remembering the details of a physics equation, and noticing small changes. Think of something at which you have a great deal of knowledge, experience, or interest. After I started studying birds I began to notice small details of bird coloring and anatomy to which I was previously blind. Architects likely notice and remember details of buildings that most people could not recall.

This all makes sense from an adaptive point of view – why waste brain power on small details that are not important to us? It is helpful to recognize the role of conscious effort in noticing and remembering details. Remembering even important details, like the location of life-saving equipment, is not likely to happen automatically.

It is worth noting that in a follow up a few months later every one of the 54 subjects in the study were able to remember the location of the fire extinguisher. Once their attention was drawn to its location, with the further reinforcement of being surprised and perhaps embarrassed by not remembering its location, that detail was encoded in their memory. This research, therefore, justifies all those tedious training sessions, fire drills, airplane lectures, and instructional videos that we have been subjected to over the years. You really should practice and study emergency procedures, locate the nearest exit, and make a conscious effort to remember important details.

This study also adds further evidence to the larger concept that our brains are highly flawed instruments. Perhaps the most important aspect of being a good critical thinker is simply recognizing that there are many ways in which we cannot rely upon our brains to be accurate and unbiased observers and recallers of reality. We need to be forever skeptical of what we think we remember, and rely more on objective external sources of information and valid processes of evaluation.

So add inattentional amnesia to your list of the many various ways in which the human brain is fallible, and think of ways to compensate for this weakness.