Saccadic masking, also known as saccadic suppression, is a fascinating and essential phenomenon in visual perception that affects us all. Our eyes move incredibly fast when shifting gaze from one point to another, for example, from left to right. This rapid eye movement is known as saccadic eye movements, also referred to as saccades.
What is a saccade?
Saccades are the rapid, jerky, ballistic movement of the eyes when we shift focus from one point or object to another. They happen frequently, up to three times per second, and help us to process visual information efficiently for tasks such as reading, following a moving object, or scanning the environment around us.
During a saccade, we have blind spots, which means we are momentarily blind to new visual input. We never notice this gap because our brain integrates information seamlessly from before and after the gap. Our eyes move incredibly fast when we shift our gaze from one point to another, and due to this high-speed movement, the image on the retina becomes blurred. This is where saccadic masking comes in.
What is Saccadic Masking?
Saccadic masking is the brain’s way of preventing saccades, motion blur during ballistic eye movements. To counteract this and ensure that we don’t perceive the gap or blur in our vision, the brain temporarily suppresses visual processing. What we are unaware of is that during saccadic masking, we are effectively blind for a split second, but the brain fills the gaps seamlessly. Although we may think we have seen all the information around us, we haven’t, due to the brain editing the information we receive.
Road Safety
In areas like road safety, saccadic masking has practical implications. The driver’s brain momentarily suppresses visual input when glancing quickly from left to right at junctions, potentially causing them to miss pedestrians and fast-moving objects such as cyclists and motorbikes.
According to Bournemouth University and DocBike, ‘A research project exploring motorcycle collisions and injury prevention has found that there are differences in motorcyclists’ and car drivers’ visual attention because they may be viewing completely different things despite being on the same stretch of road. For example, the brain naturally sees larger objects, like lorries, as threats as opposed to smaller objects such as motorcycles. To help improve awareness and encourage safer driving habits, it is important to have an understanding of this phenomenon.
The project, led by Bournemouth University’s PhD researcher Shel Silva, was match-funded by DocBike, assessed the neurological and cognitive influences of motorcyclists and car drivers. Data indicates that car drivers and motorcyclists have different visual attention patterns, due to the different types of hazards according to the vehicle type. Additionally, motorcyclists’ identification, perception, and knowledge of potential risk changes depending on their motorcycling qualifications and experience.’ https://www.bournemouth.ac.uk/news/2022-01-24/bu-docbike-research-suggests-motorcycle-collisions-could-be-caused-riders-car-drivers-seeing-different-things?utm_source=chatgpt.com#:~:text=A%20research%20project,qualifications%20and%20experience.
Our vision would be filled with distracting motion blur every time we moved our heads if it weren’t for saccadic masking. Rather than being overwhelmed by visual noise, this suppression helps to maintain a stable and continuous perception of our surroundings, allowing us to focus on important details. What we see isn’t always what is there, but what our brain allows us to see. Given the high frequency of saccades, processing every frame of visual input would be overwhelming and cause sensory overload.
Observations at Junctions
For many consecutive years, not making effective observations at junctions has been the number one reason for driving test failures. I’ve often wondered why this is the case and who/ what is to blame. Since finding out about saccadic masking and researching further, it makes sense to consider the implications of how this can be a major reason for the failings. However, outside pressures such as impatient drivers and learners also feeling under pressure not to hinder others can also be a factor as to why they may make a rash decision to emerge from junction, or enter a roundabout when it’s not safe, especially when having the added pressure of an examiner sitting next to them and they don’t want to be perceived as being hesitant.
It is important to pause and scan at junctions to ensure comprehensive scanning and make deliberate eye movements, pausing at three given points. These points should be once to the left, once directly ahead, and once to the right to check your long, middle, and short distance. If you get into the habit of doing this, your eyes will adjust faster, and you can complete the procedure quicker. This then stops the eyes from sending incomplete images to the brain. It is recommended that this be completed at least twice each time you are looking to turn. If every driver carried this out, it could reduce the risk of road accidents by one quarter. https://www.eyesite.co.uk/news/saccadic-masking-raising-awareness-in-road-safety-week.
Quick head and eye movements at junctions can lead to saccadic masking, causing drivers to miss critical visual information. When we pause, it gives our eyes and brain a chance to identify a moving vehicle/person and work out distance and approaching speed. When identifying the object, we are able to acknowledge it and determine whether it’s safe to proceed. The results could be devastating if we don’t supply our brain with this information in the first place.
The UK Parliament has acknowledged that saccadic masking may contribute to accidents where drivers fail to look properly.
Research suggests that up to 25% of such accidents could be prevented with proper driver training to mitigate saccadic masking effects. UK Parliament Committees
