Oct 02 2012

More Inattentional Blindness

If you have never seen the basketball video – take a look at it now.

This is a demonstration of inattentional blindness (or attentional blindness) – when we are focused on one task this interferes with our processing of other information. This is exactly why you should not text while driving, or even talk on the phone while driving.

The cause of this is conceptually simple: our brains have limited processing power, more limited than we would like to think. When we use some of that processing power for one task it is not available for other tasks, even basic tasks like seeing obvious things right in front of our eyes. This concept is called load theory, and researchers have documented numerous ways in which it manifests. A related concept is that of interference Рwhen we perform one task it reduces our performance on other tasks. In fact, the act of multitasking itself causes interference because multitasking requires processing power (it takes brain power to switch among more than one task)  which is taken away from each task.

Interference is probably greater for tasks that are vying for the same parts of the brain. It seems that different areas or modules in the brain participate in multiple networks engaging in different tasks. Placing a processing load on one module for different tasks causes significant interference. Some modules participate in very basic functions, like perception, attention, and memory, and therefore become overloaded very easily.

A recent study has demonstrated a new aspect of this phenomenon. Up to now research demonstrating inattentional blindness has used visual clutter to distract from seeing the target – following the basketball interfered with the ability to detect the gorilla. The new research creates the same effect without visual clutter but instead using visual memory:

Participants in the study were given a visual memory task to complete while the researchers looked at the activity in their brains using functional magnetic resonance imaging. The findings revealed that while the participants were occupied with remembering an image they had just been shown, they failed to notice a flash of light that they were asked to detect, even though there was nothing else in their visual field at the time.

This research suggests that remembering an image uses similar resources to seeing an image – that visual memory and perception are similar in terms of the brain resources that are used (which is in line with previous research).

Assuming the results of this study are reproducible, it extends the implications of inattentional blindness. Not only is texting or using a cell phone distracting while driving, the researchers suggest that trying to visualize directions or remember that image on a navigational GPS system can cause interference and reduce a driver’s ability to detect obstacles in front of them.

There are a few take-home messages from this line of research I would like to emphasize. Our brains do have limited processing power, which means if you want to optimize your performance you really should minimize distractions and forget about multitasking. While driving or performing a similarly important task where the prices of error can be extreme, it is especially important to minimize distractions. If there is someone else in the car, have them navigate, change the music channel, or do anything other than driving so that the driver can use all of their mental resources for the task at hand. If you alone and have to perform a significant task, like figuring out directions, then pull over.

All of this applies even more so to people who have any form of cognitive impairment, including those who have suffered a head injury or are in the early stages of dementia. It’s important to minimize visual and cognitive clutter and to take steps to reduce processing load.

I would also apply this principle to everyday tasks. For example, we use an electronic medical record system at my institution. In my opinion, the interface of this system is incredibly suboptimal – there is a high degree of information clutter on the screen at any one time. I find myself using a large amount of brain processing power sorting through the visual information, most of which I do not need. It’s almost as if the system were designed to be a psychological experiment in which processing load and interference were maximized. This adds to the processing load of actually practicing medicine, which itself is quite high.

In other words, this research provides neuroscientific evidence and justification for some basic principles of programming – to keep output and the user interface as clean as possible, to minimize clutter, and also to keep contrast between different pieces of information high and help draw the user’s attention to where it needs to be while avoiding popups or other distractions. I can attest to the cognitive load of systems that violate these principles.

This line of research also highlights the fact that humans are inherently bad at tasks that require maintaining focused attention for long periods of time, especially when there is a long time between significant events. While driving we are paying attention for unexpected events (like being cut off, or a sudden obstacle in the road) that rarely occur. Every time we let our attention lapse or be distracted by another task we are playing Russian roulette, hoping that nothing unexpected happens at that time, and most of the time it doesn’t. This lulls us into a false sense of security, until the day we get unlucky.


Machines, on the other hand, are excellent at maintaining consistent vigilance. They never tire or become distracted. This is why, in my opinion, self-driving cars have so much potential to reduce car accidents and improve traffic flow. Already Google has cars driving around the city going many miles between the need for driver intervention. Eventually we will likely have fully automated cars, but very soon we will likely have computer assisted driving. A human will still be in control, but an onboard system will help avoid collisions and keep cars in line and at a proper distance from other cars.

The only downside of this I can see is that drivers will become lazy and complacent behind the wheel, comfortable in the knowledge that the onboard system will take over if they lapse. It’s just another way in which we are delegating our cognitive tasks to computers. Perhaps this is not a downside, however. If we can offload a lot of our daily cognitive tasks to computers we can free up human brain power for more important or creative tasks. We may become increasingly dependent on our machines, but also have increasing potential to create and think.

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