9 SMIDSY – looked but not perceived; inattentional blindness

SUMMARY – ‘inattentional blindness’ does not mean that drivers are “not paying attention”… it occurs when we are tightly focused on one particularly demanding task at the expense of other, apparently less-demanding tasks… we fail to notice anything that’s not part of that immediate task…


In the last post, I looked at the effect of workload and how when involved in a difficult and potentially stressful task, objects that we would otherwise likely see actually go unnoticed. As Pammer et al (2017) noted:

“When we are driving, there is a huge amount of sensory information that our brain must deal with. We can’t attend to everything, because this would consume enormous cognitive resources and take too much time.”

It’s actually more complicated than that. They continue:

“So our brain has to decide what information is most important. The frequency of LBFTS crashes suggests to us a connection with how the brain filters out information.”

The team recruited fifty-six adults and asked them to examine a series of photographs depicting routine driving situations taken from the driver’s perspective. The respondents were to determine whether the image represented a safe or unsafe driving environment. In the final photograph, the researchers manipulated the image to include an unexpected object, either a motorcycle or a taxi, and asked participants if they noticed either object. A total of 48% of all participants failed to notice ANY additional object. But significantly more failed to detect the motorcycle (65%) than didn’t spot the taxi (31%).

It’s been known for a long time that when we are focused on performing a ‘high load’ task where we are processing some specific information, it reduces our response to other objects which are unexpected but in plain sight. Take a look at this YouTube video – you may have seen it before:

The task the viewer is required to perform is moderately complex, involving focusing our eyes carefully on the ball, whilst adding up in our head. This has become a classic experiment, and it turns out round 50% of people are taken by surprise by the events. Now, if you are amongst that 50% (and for what it’s worth I was the first time I saw it!), you might begin to find it a little easier to believe that a driver performing the complex task of monitoring the movements of other vehicles whilst deciding if there is a safe gap to turn into, might fail to spot a motorcycle approaching a junction. (It’s also worth mentioning that some of the subjects, on being told what they had missed and viewing the video a second time, were convinced that it was a trick and that the object they missed had been added to the second video. They had as much difficulty believing they’d been fooled as the motorcyclist who refuses to believe that a driver could ‘look but fail to see’.)

Rather unfortunately, this phenomenon is known as ‘inattentional blindness’. The term  ‘inattentional’ unfortunately leads motorcyclists to believe it confirms what they think they already know – that drivers “aren’t paying attention”, and that if drivers were ‘attentive’ instead of ‘inattentive’ it would fix the problem. It’s a complete misunderstanding. Inattention blindness occurs when we ARE paying attention but tightly focusing on on a particular part of the visual field and performing a highly-demanding task. As a result, we fail to perceive an unexpected stimulus that is in plain sight. In short, we simply don’t have the brain power to spare. (The term itself dates back to 1992 and a book by the same name which might more usefully have called it ‘attentional blindness’.)

In an article on the University College London website, researchers under Professor Nilli Lavie of the UCL Institute of Cognitive Neuroscience, looking at just why our brain becomes ‘blind’ under high load. Lavie says:

“Engaging attention on a high load task has a strong effect on the brain’s response to the rest of the world. It reduces both the level and precision, or ‘tuning’, of neural response to anything else around us that is not part of the task.“These effects of load on neural response explain inattentional blindness. Although our environment hasn’t changed, the change in our brain response under load leads to inability to perceive otherwise perfectly visible stimuli outside our focus of attention.”

So here’s a second video to watch. The task is the same. Count the passes.

Even though I KNEW there would be some kind of new event happening in the video – after all, I had been mentally primed to be on the alert after seeing the first one, I still failed! That’s because there’s even more going on, and even more of a cognitive load on my brain. Even though I knew I needed to pay attention to the big picture, my brain STILL shut down any visual input it thought was irrelevant to the task in hand. And because I was looking so hard for the other events, I miscounted the passes.

Back to Lavie:

“When we perform a task which demands processing a high information load, it takes up most or all of our brain capacity for perception of any other information, so our processing becomes selective. We’re able to continue attending to the relevant task, but our brain no longer responds to irrelevant information.“These effects of load are beneficial when it comes to distraction; we can ignore irrelevant distractions more effectively under high load. But it also leads to inattentional blindness, where we can’t perceive unattended stimuli that are not part of the task – even in cases when it’s quite important to perceive them – for example, an animal on the road while we’re driving.”

One theory is that our eye movements are controlled by two processing centres that are in constant competition. Crundall (2008) explains:

“The fixate centre keeps the eyes in one place, and continues to process the current stimulus, while the move centre continually places demands on the oculomotor system for the eyes to move to a new area of interest. These two centres actively inhibit each other, so if the information at the point of fixation is extremely important the fixate centre will inhibit the move centre. However, if the move centre is more active, then the eyes will be dragged away from the point of fixation, potentially before the viewer has finished processing what they were looking at.”

In other words, when looking at an environment with a number of moving objects, we can look right at an object and have our eyes drawn away from it towards something that demands more visual attention. Inattentional blindness should not be seen as a criticism of drivers. Instead we should recognise that the human brain was never designed for driving and the only way ALL road users (motorcyclists included) can make the best use of the human brain’s limited attentional and/or processing capacity is to be selective in where to concentrate attention.

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References:

Crundall, D., Clarke, D., Ward, P., Bartle, C. (2008) “Car Drivers’ Skills and Attitudes to Motorcycle Safety: A Review – Road Safety Research Report No. 85, Department for Transport: London” School of Psychology, University of Nottingham

Pammer, K., Sabadas, S., Lentern, S. (2017) “Allocating Attention to Detect Motorcycles: The Role of Inattentional Blindness. Human Factors”: The Journal of the Human Factors and Ergonomics Society

UCL News ‘Inattention blindness’ due to brain load 17 July 2012
http://www.ucl.ac.uk/news/news-articles/1207/17072012-Inattention-blindness-due-to-brain-load-Lavie

Last updated:

Friday 23 November 2018 – minor edit for clarity

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