License to Learn

Our limited bandwidth

June 1, 2010

Anyone who has flown behind a panel full of glass in a technologically advanced aircraft knows how easy it is to be overwhelmed by information. Yet many pilots seem to handle the data and their cockpit chores with grace and aplomb—and all without having extraordinary levels of brain-processing power. That’s a good thing, because on the conscious level, our mental resources are strikingly limited.

I hate to tell you this, but you have a Stone Age brain. Don’t feel bad. Everyone received the same starter package at birth. It seems that our brains haven’t really developed much over the past 100,000 years, particularly in the area of short-term (working) memory. For early man to survive, it apparently took no more than the ability to hold about seven distinct items in his working memory at a time. That’s not much, but it was enough for Fred Flintstone. Unfortunately, the number seven doesn’t always work for pilots.

Psychologist George Miller, in a now-famous study on the limits of human information processing, found that we are able to keep about seven distinct items in our head at one time (our working memory). In his book, The User Illusion, Tor Norretranders suggests that this represents a bandwidth of human consciousness of approximately 2.8 bits/sec (a binary “on-off” state represents two separate items, which is one bit. So 2, times itself 2.8 times, is nearly 7). Of course, we can perceive many things in units of time smaller than a second, which increases this bandwidth slightly—but not by much, according to many researchers. Sure, millions of bits of information may enter the brain, but the outward expression of our working memory’s seven-item limit is, in a large way, how we define consciousness. Throw a handful of pennies on the table and you’ll find it difficult to isolate and recognize more than seven “distinct” entities at once. Beyond seven pennies, we begin to perceive them as a mass of coins, in lieu of their individual states.

This is one of the big reasons we can’t “simultaneously” focus all our attention on copying a clearance and simultaneously evaluating our Nexrad readout. Both activities have data points far exceeding seven, and far exceeding our mental resources.

But wait! Aren’t pilots supposed to be good at multitasking—focusing on two or more things at once? I’m sorry to say that multitasking is an urban myth in the sense that we can’t focus 100 percent of our attention on two things simultaneously. It’s either 25 percent here and 75 percent there, or the same pie divided in differing slices. So what happens to pilots when they attempt to pay attention to several things at once? The current research on cell phone use and driving helps answer this question for us.

Researchers at Carnegie Mellon University used their melons to discover that cell phone use (hands free or not) behind the wheel reduces the brain activity associated with driving by 37 percent. And the University of Utah found that cell phone use reduced a driver’s reaction time as much as having a blood alcohol concentration of 0.08 percent (the limit at which you’re presumed legally drunk in most states). The process by which cell phones engage our brain to disengage our performance is known as cognitive capture. This results when one activity (the conversation) limits or diminishes the attention we’re paying to another activity (driving). It’s not much of a stretch to imagine how advanced cockpit instrumentation might similarly capture our attention, thereby reducing our situational awareness and reaction time.

So how is it that some pilots safely operate advanced airplanes without becoming overwhelmed? There are several answers to this question, but the most important one may surprise you. After gaining sufficient experience, these capable pilots learn how to say one very important word to themselves and others. They learn how to say “no.” It is the word, no that separates the pros from the amateurs. Those who know are those who say no. The pros say no to anything that distracts them from the prime directive of airmanship: fly the airplane first. Isn’t this the same thing that drivers should be saying to themselves regarding cell phone use? Drive now, talk later. Flying the airplane is a pilot’s first priority. Anything that distracts from this objective should be handled with a stern no, be it the demands of their navigational equipment or requests from ATC.

Once the airplane is under control (physically or via a monitored autopilot), then pilots should say no to anything that distracts them from navigating properly. With that accomplished, they say no to anything that distracts them from communicating with ATC. Expressed succinctly, they aviate, navigate, and communicate, in that order. The pros say no to anything that interferes with that priority sequence. It’s the most important step we can take to prevent cognitive capture in the cockpit. Knowing our cockpit priorities helps us allocate our limited consciousness resources in the most responsible way.

Years ago, my friend Skip Forster (when he was president of a major simulator company) offered an interesting insight into the minds of professional pilots. When displaying at an airshow, he said he could always tell when an airline captain was flying one of his simulators:“They always do two things. They stare at the attitude indicator and they don’t let anyone distract them when they fly.” Said another way, they were consistent in saying “no” to distractions.

Longtime flight instructor Rod Machado recently published his newest book. Visit the author’s blog (

Topics Pilots