Pete’s Blog

Sheffield Advanced Motorcycling - Pete Harley (National Observer

Editors note: Here is the second article, sorry it’s a couple of days later than planned, written by Pete Harley (Observer). We are very grateful to Pete for taking the time to produce these well-researched articles. Share them with your friends to that the SAM Club rich with very talented bikers. Thank you.

Hello again

In the last article I was talking about what could probably be grouped as “illusions”.  In particular, I am interested in those situations where the brain has “interfered”.  In the model from the diagram in the previous article it is clear that there are (at least) three parts contributing to what you see: your eyes; your optic nerves; and your brain – as I mentioned there I want to explore the third contributor, your brain.

The reason for this is a basic idea that I’ll probably return to again and again: What you ‟see” isn’t necessarily what’s there or, alternatively, What you see may not be there at all.  I’m sure that you’ll agree that either situation might be worrying in the context of riding a motorcycle so let’s explore these possibilities a bit more.

First of all, I ought to mention one input to you vision that happens before any information is transferred into your brain – your blind spot”.  This occurs because at the point where the optic nerve attaches to the eye there are no rods or cones – the fundamental constructions that react to the presence (or lack) of light and pass that information to the brain via the optic nerve.  This means that anything in your line-of-sight that “coincides” with that blind spot could be “invisible”, at least partially.  This effect can be demonstrated using the following diagram (remember, clicking on the diagram takes you to the appropriate website):

Sheffield Advanced Motorcyclists -
(Flip the diagram from left to right or turn it upside down so that you can check the effect on your other eye.)

One lesson we can draw from this diagram concerns the size of the spot that disappears – this is more than large enough to cover the sight in your off-side mirror of a fast-moving car in the outside lane of a motorway.  The obvious solution to this problem is not to fix your gaze on one spot – make sure that you are scanning continually so that you blind spot will also be moving and the chance of it hiding something important is reduced.  This is a “solution” that may appear again in these articles.

Now, on to your brain. I’m going to start with an illusion that we’ve not mentioned before:

Keep staring at the black dot…

After a while the grey haze around it will appear to shrink.  If your eye moves then the haze will reappear.

The next one is called Motion Induced Blindness; to get the benefit of this one you really have to have a look at the demonstration on the linked website (there are lots of other illusions there as well.)  The Point of this one is that things that are, quite clearly, in the picture disappear from time to time. 

Sheffield Advanced Motorcyclists - motion induced blindness
2. Can you see the triangles?

The hows and whys of this illusion I’ll leave to others but, as before, if you scan continually then the illusion itself disappears.

The point of these illusions is to emphasize the importance of scanning continually – don’t let your eyes fix on a single point for any length of time.  This may be why your eyes move in saccades1:

Sheffield Advanced Motorcyclists - scanning the road
http://suncityvision.com/eyemovements

Now, I think it’s time for some entertainment:

Sheffield Advance Motorcyclists - learning whilst having fun!
https://www.sciencealert.com/watch-this-awesome-illusion-turns-rectangles-into-circles-in-the-mirror

Go to the website to see something amazing!

Until next time, keep your eyes moving, take care and stay safe!

Pete

 

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