October 2, 2012
Study Examines How Memory Load Causes ‘Inattentional Blindness’
Alan McStravick for redOrbit.com - Your Universe Online
How many times have you driven a route that you were familiar with, made it safely to your destination, and then realized that you can´t recall any of the specifics of your journey? Maybe you were focusing on the music on the radio or the stress of the day. Perhaps in our increasingly digital existence, you were paying attention to incoming texts or listening to the turn-by-turn directions of your GPS unit.
This psychological condition, known as ℠inattentional blindness´, occurs when we increase our memory load with information that deflects our attention from the task at hand. When we are focused on tasks or specific information, we can sometimes be effectively blind to things that are in plain sight.
Numerous real-world examples have been documented over the years. Workers in the medical or law enforcement fields — professionals regarded as educated, intelligent and even methodical — have botched their jobs in a manner that appeared careless or negligent and often led to dangerous or even fatal outcomes on account of inattentional blindness or the related phenomenon known as 'inattentional deafness'.
According to a new study commissioned by the Wellcome Trust, when we try to keep an image we´ve just seen in our memory, we can blind ourselves to things we are actually looking at.
A fun example, the now famous 'invisible gorilla' experiment, involves observers who are watching a video of basketball players passing around a basketball. They are asked to focus on and count the number of times the players pass the ball to one another. While focused on this task the observers fail to see a man in a gorilla suit who walks directly across the center of the screen.
While the ℠invisible gorilla´ experiment is an interesting way to explain this phenomenon, not all examples are so light-hearted. In 1995, while responding to a downed officer, several police cars began to pursue four suspects who had fled in a car. According to Dick Lehr, a reporter for the Boston Globe, “Cops were flying in from all over. There were more than 20 cruisers involved at different points in the chase.” The vehicle chase finally came to an end in a cul-de-sac when all four suspects fled on foot in different directions.
According to reports, the first officer to give chase on foot was undercover officer Michael Cox. As a gang unit officer, Cox was in plain clothes. Cox was also black. In the heat of the moment, other officers mistook Cox for one of the suspects and gave chase, eventually catching him and knocking him to the ground.
Lehr´s report of the incident stated, “Suddenly he´s hit in the head from behind. And they do a Rodney King on him. He´s beaten in the head, and beaten on all fours, he´s down and the cops are whaling away on him.”
This instigating incident is where we meet Officer Kenneth Conley. Because of what he saw, or more accurately, didn´t see, he was eventually convicted of perjury and obstruction of justice. Though he passed within remarkably close range of the beating of Cox, Conley claimed that he did not see the brutal police beating as he was giving chase to one of the murder suspects.
"Common sense would say that he had to see something," Lehr says. "Whether it's two feet away or five yards away, [the beating] is in his area, his radar, so to speak."
It was only after Conley ran by the other officers beating that Cox came to the realization that they had made a tragic error. The beating of Officer Cox finally ceased, but the officers didn´t rush in to help their victim.
"Those cops sort of disappeared into the shadows of the night," Lehr says.
According to the numerous investigations conducted in the aftermath of this night, no officer present would admit they had participated in the beating of Officer Cox or even that they´d seen the beating.
"There were like 20 or 30 police reports written that night," Lehr says. And they all essentially said, “℠I was over here, I don't know what happened, I didn't see anything, all I know is that we found Mike there.´”
All, save one. Officer Conley was the only officer who admitted to being near where they the beating occurred. He testified in court that he was right there. The only similarity between Conley´s testimony and the other officers was his insistence that he hadn´t seen a thing.
Lehr reported, "Conley kept saying over and over again, 'I didn't see anything, I don't know why I didn't see anything, I wish I had seen something.'"
Due to the culture of protection within the law enforcement community, investigators had serious doubts about the truthfulness of Conley´s story and suspected that he was lying to protect his fellow officers.
At trial, Conley was eventually found guilty on counts of perjury and obstruction of justice and sentenced to serve 34 months in prison.
It was only after a re-enactment of the crime scene by two psychologists whose area of study focused on inattentional blindness that enough evidence was found to overturn Conley´s conviction.
While these examples are drastic by their very nature and focus on how inattentional blindness is affected by clutter in our visual field, a new study aims to show that the condition does not always require visual focus on one specific point. Rather, evidence indicates that we can also experience inattentional blindness while we mentally focus on trying to remember something we have just seen.
Professor Nilli Lavie from the UCL Institute of Cognitive Neuroscience in London led the study and explains: “An example of where this is relevant in the real world is when people are following directions on a sat nav [GPS navigator] while driving.”
"Our research would suggest that focusing on remembering the directions we've just seen on the screen means that we're more likely to fail to observe other hazards around us on the road, for example an approaching motorbike or a pedestrian on a crossing, even though we may be 'looking' at where we're going."
Study participants whose brain activity was being monitored via functional magnetic resonance imaging (MRI), were given a visual memory task to complete. Researchers found that while the participants were focused on remembering an image they had just been shown, they failed to notice a flash of light they had been asked to detect despite the fact that there was absolutely nothing else in their visual field at the time. In control trials where they were not asked to remember anything, the flash of light was easily detected.
Researchers have termed this phenomenon ℠load induced blindness´. They also noted that there was a significant reduction in activity in the primary visual cortex — the area of the brain that processes incoming visual information — when the participants´ minds were not ℠loaded´ with the task of remembering the image.
Professor Lavie adds: "The 'blindness' seems to be caused by a breakdown in visual messages getting to the brain at the earliest stage in the pathway of information flow, which means that while the eyes 'see' the object, the brain does not."
First proposed more than a decade ago by Professor Lavie, load theory is the idea that there is competition in the brain for limited processing power. It helps to explain just how the brain can mysteriously fail to detect even the most conspicuous events that cross the visual field, like the above mentioned ℠invisible gorilla´.
These findings, published in the Journal of Cognitive Neuroscience, reveal a pathway of competition in the brain between new visual information and our short-term visual memory that wasn´t understood or appreciated previously. In other words, the act of remembering something we´ve seen that isn´t currently in our field of vision can mean that we literally don´t see what we´re looking at.