Nearly the worst air disaster and using phones while driving: A grim connection
How the pilot of Air Canada Flight 759 could not see four large aircraft in front of him is intriguing
Most of the laws banning cell phone use while driving have focused inappropriately and exclusively on handheld phones. Whether or not cell phone use while driving should be regulated is a political question, but the cause of the distraction is an empirical one. Public officials do a disservice when they fail to convey the real reasons why using a cell phone while driving is dangerous.
According to Christopher Chabris and Daniel Simons, authors of the book The Invisible Gorilla, "The enforcement campaign spreads misinformation by implying that it’s the 'handheld' aspect of cell phone use that causes the problem. In reality, the real distraction has nothing to do with having both hands on the wheel — it’s the conversation itself (coupled with the challenge of communicating with someone not in the car). Using a hands-free phone doesn’t eliminate the distraction, and it might even be giving people a false sense of confidence if they think that switching to a hands-free phone makes them safer." The brain does not register unexpected events.
A trained driver is proficient in managing a car and driving with one hand on the steering wheel is not an exception. There are times when one completes a journey and at the end of it is unable to recall the route taken to reach the destination whereas all turns and stops were executed safely. In this scenario, the driver would have been lucky that another vehicle or a pedestrian did not appear in front of him unexpectedly since the brain will not register these unexpected events. This phenomenon is called inattentional blindness (IB).
The pilot of Air Canada Flight 759 approaching to land at San Francisco on July 7, 2017, aligned the aircraft to land on a taxiway that had four big jets carrying over 1,000 passengers.
The pilot mistook the taxiway for the landing runway and continued to descend over the taxiing aircraft to reach the lowest height of 60 feet before realising the mistake and taking evasive action. How the pilot could not see such large aircraft in front of him is intriguing.
Flight profile of Air Canada Flight 759 (Image courtesy: Open source NTSB report)
Inattentional blindness (IB)
Everyone has some awareness of the limited capacity of attention, and our social behaviour makes allowances for these limitations. Intense focusing on a task can make people effectively blind, even to stimuli that normally attract attention (Kahneman, 2011). When engaged in a demanding task, attention can act as a set of blinders, making it possible for salient unexpected stimuli to pass unnoticed right in front of our eyes (Neisser and Becklen, 1975).
This phenomenon of 'sustained inattentional blindness' is best known from Simons and Chabris’ (1999) study in which observers attend a ball-passing game while a human in a gorilla suit wanders around. Despite having walked through the centre of the action, the 'gorilla' is not reported by a substantial portion of the observers.
Does IB still occur when the observers are experts highly trained on the primary task? By some estimates, medical errors, including missed radiological abnormalities, are the third leading cause of death in the US. "We’ve known for a long time that many errors in radiology are retrospectively visible," University of Utah researcher Trafton Drew says. "This means if something goes wrong with a patient, you can often go back to the imaging for that patient and see that there were visible signs — say, a lung nodule — on something like a chest CT."(Drew, Vo and Wolfe, 2013)
In computed tomography (CT) lung cancer screening, radiologists search a reconstructed 'stack' of axial slices of the lung for lung nodules that appear as small light circles. In a series of experiments conducted with 24 radiologists (mean age: 48; range 28–70), they had up to three minutes to freely scroll through each of the five lung CTs, searching for nodules as their eyes were tracked. Each case contained an average of 10 nodules and the observers were instructed to click nodule locations with the mouse. On the final trial, a gorilla with a white outline was inserted into the lung.
'Gorilla in the lung'
In the experiment, 20 of 24 expert radiologists failed to note the gorilla, the size of a matchbook, embedded in a stack of CT images of the lungs. This is a clear illustration that radiologists, though they are expert searchers, are not immune to the effects of IB, even when searching medical images within their domain of expertise. Potchen (2006) showed that radiologists could miss the absence of an entire bone.
Why do radiologists sometimes fail to detect such large anomalies? Of course, as is critical in all IB demonstrations, the radiologists were not looking for this unexpected stimulus. Though detection of aberrant structures in the lung would be a standard component of the radiologist’s task, our observers were not looking for gorillas. Presumably, they would have done much better had they been told to be prepared for such a target. Moreover, the observers were searching for small light nodules.
The reason the Air Canada crew did not sight the four large passenger jets can be attributed to IB. The fatigued crew had aligned the aircraft with a taxiway due to an expectation and confirmation bias.
With limited cognitive capacity and analytical skills due to fatigue and biases, the crew further got a confirmation from the Air Traffic Control (ATC) that the runway was clear. During the approach to land, the pilot’s attention was focused to keep the aircraft on the lateral and vertical profile that is, maintain the centreline and aim for the touchdown point.
Pilots do not normally expect or look out for aircraft on the runway since they assume that the ATC is controlling the access to the runway. IB sets in when maximum attention is focused on a particular activity.
Here the crew members were focused on the dimly-lit taxiway and trying to fly a vertical profile with limited guidance, as a result of which they were blinded to unexpected objects in their field of vision. It relates to the gorilla in the CT scan experiment, which could not be detected since the radiologists did not expect it to be there and were focused on looking for smaller-sized images.
These are human cognitive limitations, which have been highlighted in other transport accidents. The crew members need to be aware of their limitations, especially when a task demands too much attention and/or when they are fatigued. Awareness of one’s limitations, trusting the instruments and having adequate cross-checking with the crew members and ATC can help to prevent bias.
(This article first appeared in safetymatters.co.in)