Inattentional blindness

In Legal Lines, October 20216 MinutesBy Danielle BestonNovember 8, 2021

Inattentional blindness (“IB”) occurs when we fail to notice an unexpected object or event, which is fully visible. We readily see the object if we look for it, but we fail to see it when our attention is on other things. The failure to perceive an unexpected stimulus in plain sight results from a lack of attention rather than any visual defects or deficits.

This concept is important in the context of professional drivers because it can explain why you didn’t see a smaller vehicle that turned in front of you until there was a collision.

The invisible gorilla

Humans have a limited mental capacity which makes us incapable of attending to all the sights, sounds and other inputs that rush the senses every moment. Inattentional blindness is beneficial in the sense it has evolved to help filter out irrelevant input, allowing only important information to reach consciousness. This allows humans to focus our limited mental resources more efficiently in our environment.

One of the most well-known demonstrations of IB is a video that shows a group of people passing a basketball back and forth. Half the group is wearing white uniforms, and the other half black. Participants in the study are asked to watch one team or the other and count how many times the ball is passed from one player to another. Almost one-third of the people watching the video fail to see a person in a gorilla suit walk through the middle of the game. It is not a trick – once you are told about the gorilla, you see it. We are so busy looking at and counting the passes between players that we fail to notice the gorilla because its presence is unexpected. This effect is IB.

The item that is not seen is referred to as the incongruent stimuli. It is hiding in plain sight. In my experience as a traffic lawyer, there seems to be a disproportionately large number of accidents involving motorcycles and cyclists. One explanation for this could be that they are the incongruent stimuli on New Zealand roads: they are there, but some drivers don’t see them. Studies show us that intersections are among the most dangerous places for motorcycle collisions due to other vehicles violating their right of way, which could be due to IB.

Looming and motion camouflage

Due to the small front profile of motorcyclists and cyclists, they do not benefit from an effect called ‘looming’ as larger vehicles do. When an object is moving towards or away from the human eye it is called Z-motion. When an object is moving laterally across the field of vision of the human eye, it is called X-motion. The human eye picks up and perceives X-motion much easier than it does Z-motion. Looming is the rate of expansion of an object that is exhibiting Z-motion. An object will double in size with each halving of the distance from the viewing point. Due to the small front profile of a smaller vehicle when it is approaching you from a distance, its perceptual size does not increase as rapidly as a larger vehicle, and the human eye has trouble perceiving its approach.

Further complicating things is something called ‘motion camouflage’. This phenomenon has been studied in the animal kingdom by observing dragonflies. Research has demonstrated that a dragonfly can move rapidly towards its prey while appearing stationary and remaining undetected. By following a prescribed pattern of motion that continually places the dragonfly between the target and some landmark, the bug doesn’t create any X-motion and exploits its minimal Z-motion. This explains why motorcycles and cyclists may inadvertently be camouflaged into background landscapes and therefore be hidden from view.

The pitfalls of experience

Being aware of IB means that we should do everything we can to prevent getting into a situation where we may fail to notice an unexpected object or event. Alarmingly, experienced drivers are more susceptible to IB because studies show that they adapt through time to perform driving as an automated process, neglecting uncommon vehicles encountered on the roads even if they are conspicuous. The ‘experience’ a driver accumulates develops their ‘perceptual set’. This means that what you expect to see determines to a large extent what you actually see.

Recent studies have also looked at age differences and inattentional blindness scores, and the bad news is that results show that the effect increases as humans age. So, to avoid an IB episode, be vigilant to ensure that you’re not just driving on autopilot because you are familiar with the route.

Please note that this article is not a substitute for legal advice, and if you have a particular matter that needs to be addressed, you should consult a lawyer. Danielle Beston is a barrister who specialises in transport law. Contact her on (09) 379 7658 or 021 326 642.