Motion Induced Blindness – SMIDSY

The following is an email discussion about the problem, well illustrated at

Another visual effect that can lead to drivers not seeing other road users, if they scan too quickly, is called Saccadic Masking and is explained at


From: Idris Francis []
Sent: Thursday, September 20, 2012 7:08
To: Recipient list suppressed:
Subject: Re: Fwd: Re: Re: Motion Induced Blindness – IMPORTANT

thanks, Mike, interesting, circulating for comment. I wonder whether any IT reader can modify the software to remove or prevent the blue background rotating – or perhaps easier write software that omits it?

Just before reading yours I was thinking about how I look ahead when driving – and it’s not constantly scanning as pilots do. Instead I think I relax my gaze to cover a wide area, and focus on a small area on when something happens there – like the bonnet of a car coming around a blind bend, or a child’s feet beneath a parked car.

The danger then seems to be that once focused on whatever it is, I get blind spots elsewhere. This suggests that one problem ahead at a time is fine, more than one is dangerous.

The scale of importance of this blind-spot problem is indicated by the Derbyshire primary causal factor report for 2010/11, showing that “failed to look properly” (aka “looked but did not see”) accounted for 690 out of 2,220 injury accidents or 31%.

This incidentally compares to 69 (2.7%) for speeding - confirming yet again that the authorities have the wrong priority.

One curious aspect of the report is that “loss of concentration” is not specifically identified despite year-long experiments in the USA with many cars fitted with CCTV monitoring the driver confirm that (even momentary) loss of concentration preceeds about 70% of all road accidents. I must check again what the Stats19 forms and Stats20 instructions specify



At 06:51 20/09/2012, you wrote:

On 20/09/2012 03:48, Idris Francis wrote:

Douglas, as you might get, is an optician…….


From: Douglas <>
To: info <>
Date: Wed, 19 Sep 2012 16:37:41 -0400
Subject: Re: Re: Motion Induced Blindness  – IMPORTANT


The phenomenon of fading perception of stabilised retinal images was known from 1950 and mentioned when I was a student in the late 1960s.

If the image on the retina does not move around significantly (as it does normally with micromovements called saccades – i.e. the eyball ‘jiggles’ about naturally all the time) then the image perceived fades and disappears. The person becomes blind in effect.   In the case of the illusion shown, peripheral vision is affected and fades with close central fixation,  but is probably a more sophisticated mechanism than just simple retinal image stabilisation.

It is just another of the amazing psycho/physiological phenomena of vision. But there are many others more astonishing.

Take for instance the fact the light rays have to pass through the blood vessels from the central retinal artery and veins which sit on top of the retina (in front towards the lens and pupil where the light is coming from) in a tree-like pattern right across the retina – yet are not perceived at all – but where they must necessarily reduce the light passing through them and thus give a ‘negative’ effect on the retina like the method in photography of putting a leaf on photographic paper in sunlight to give a leaf with veins pattern on the photo. If however the light rays pass slightly to one side – such as when I use an ophthalmoscope to look into someones eye and look into the periphery at an angle – suddenly they see in full relief the retinal blood vessel tree as the light strikes retinal receptors not normally under the retinal blood vessel tree. The retinal blood vessels are completely cancelled by the retinal receptor cells somehow,  in all their exactness of colour and light pattern density in the brain.

Visual science knowledge of perception is still in its infancy.

Stabilized Images are images on the retina that are unaffected by microsaccade or ocular microtremor (OMT). Experiments by Riggs and Ratliff (1950)[1]) established the remarkable finding that stabilized images result in the fading and disappearance of the visual percept. Some think that this demonstrates adaptation of the sensory retinal cells, but it may have a more profound involvement in the functioning of neural cliques, cell assemblies (cf. Hebbian theory) and patterns for memory. Images can be stabilized mechanically with optics mounted on the eye itself, or the eye can be braced mechanically so that its motion is drastically reduced.


—– Original Message —–

From: Idris Francis

To: Recipient list suppressed:

Sent: Wednesday, September 19, 2012 1:10 PM

Subject: Fwd: Re: Motion Induced Blindness – IMPORTANT

I realised years ago that if I concentrate on a single area for any length of time I then find myself concentrating on a single part of that area, and so on and so on.

This is also relevant to trying to fly radio control models when there is more than one in the air, or when there are obstructions such as trees or bushes.It might also explain a photograph I heard of years ago, of a French army truck piled into a tree – the only one in a vast expanse of desert!


From: Paul Withrington <>

To: Paul Withrington <>

Date: Tue, 18 Sep 2012 09:21:11 -0400

Subject: FW: Motion Induced Blindness

Very relevant to the significant number of “looked but did not see” causal factors of accidents in Stats19 reports -



Subject: Re: Motion Induced Blindness


Motion Induced Blindness

In a motor accident, wherein a speeding car hits a slower moving vehicle coming from the side, the speeding car drivers often swear that they just didn’t see the vehicle coming from the left or right.

Well, they aren’t lying. They really don’t see the vehicle coming from the side, in spite… of broad daylight. This phenomenon on the car drivers’ part is known as Motion Induced Blindness. It is unbelievable but it is true, and it is definitely frightening. Armed forces pilots are taught about motion induced blindness during training, because it happens faster at high speeds; and to some extent it is applicable to car drivers also, especially the fast ones. So, if you drive a car, please read this carefully.

Once airborne, pilots are taught to alternate their gaze between scanning the horizon and scanning their instrument panel, and never to fix their gaze for more than a couple of seconds on any single object. They are taught to continually keep their heads on a swivel and their eyes always moving. Because, if you fix your gaze on one object long enough while you yourself are in motion, your peripheral vision goes blind. That’s why it is called motion induced blindness. For fighter pilots, this is the only way to survive in air; not only during aerial combat, but from peacetime hazards like mid-air collisions as well.

Till about three decades ago, this ‘heads on swivel & eyes moving technique was the only way to spot other aircraft in the skies around.

Nowadays they have on-board radars, but the old technique still holds good. Let me give you a small demonstration of motion induced blindness. This is the same demonstration that is used for trainee pilots in classrooms before they even go near an aircraft. Just click on the link below. You will see a revolving array of blue crosses on a black background. There is a flashing green dot in the center and three fixed yellow dots around it. If you fix your gaze on the green dot for more than a few seconds, the yellow dots will disappear at random, either singly, or in pairs, or all three together. In reality, the yellow dots are always there. Just watch the yellow dots for some time to ensure that they don’t go anywhere!

(You can alter the background color or the rpm of the array by clicking the appropriate buttons.

so, if you are driving at a high speed on a highway and if you fix your gaze on the road straight ahead, you will not see a car, a scooter, a buggy, a bicycle, a buffalo or even a human being approaching from the side. Now reverse the picture. If you are crossing a road on foot and you see a speeding car approaching there is a 90% chance that the driver isn’t seeing you, because his/her peripheral vision may be blind! And you may be in that blind zone!



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