I think the answer is 'yes' people do have different tolerance of flickering or flashing images. I can't explain why, though.

For a few years I worked as a computer support bloke and I must have sat in front of hundreds of monitors per year. I would find it immediately irritating if the screen was refreshing at 60Hz (we're talking CRT screens here) and I would have to switch to 72Hz, which I found comfortable. It always amazed me that most users were totally unaware of the flickering even when I pointed it out.

Like Pete, I do not have a detailed explanation for you. However from personal experience I think that there are at least two or three effects at work.

Slightly to my surprise, neither of you mentioned that the effect, especially in terms of irritation, is at its worst when one sees it from the corner of one's eyes. Although I never have been more than mildly irritated by such screens, such irritation as I did experience tended to be because I would move my eyes, possibly to look down at paper, and as soon as I moved them there would be the flicker from the corners of my eyes, distracting my attention and thereby becoming irritating. Once I got used to it, though it certainly was not fun, it became more easily bearable.

I suspect that it is not so much that your son has different eyes, as that his mental processing is not so badly distracted by the effect. Mind you, I have a reservation on that point, as you will see in the next paragraph.

Now, one of the main differences between that part of your retina that receives the part of your view on which you focus, and the part that deals with peripheral vision, is that the light receptors dealing with peripheral vision tend to be less densely packed, and to have fewer cones and more rods. Accordingly they are more sensitive to low intensities of light and less sensitive to colour and detail.  I suspect that accordingly they can detect flicker (change in intensity) more sensitively than light receptors in the centre of the field of vision. However it also is a fact that men tend to have poorer peripheral vision than women. That is why I have my reservations on your son's eyes being identical to your daughter's.

The other effect has to do with the way that your eyes and brain deal with moving events. There are fundamental reasons why you cannot do that without reference to external visual clues plus your internal calculations of how you are moving and how other things are moving. To keep detailed account of such factors, your visual system largely ignores what is going on during your own movements and rationalises what you see in terms of your own control of your eyes. For a quick demonstration of the difference between what you see when your eyes are under your mental control, and when not, look at something on your screen and move your head and eyes in various ways. Everything should look consistent to you. The screen should look in focus, and stable in position.

However if you put a finger against the outer edge of your eyelid, and gently push your eyeball out of position, you will see an immediate shift in the view that eyeball presents to your brain. Specifically your to eyes will no longer see things as being in the same position and you will get obvious double vision. There are many such effects. Looking at a television set, and making suitable buzzing noises with your teeth barely parted, or rattling your tongue with a violent "rrr" noise, you can make your eyeballs vibrate and the television image will dance about wildly.

A more interesting effect based on that principle (an effect that is inclined to give some people instant nausea) is if you use binoculars, especially looking at distant bright lights in the dark. Without binoculars all the lights look perfectly stable, but with binoculars, if you shift the field of view even slightly, each light begins to leave visual trails. Incandescent lights leave more or less continuous trails, whereas fluorescent lights and LEDs leave strings of dots, or at least strings of beads. Similarly, if you take an LED device and move it rapidly in front of your eyes in pitch dark you will see that it leaves an impression of separated images. And if you ever have danced under strobe lights, you will have noticed that it is almost impossible to follow trajectories of motions. For example I cannot catch a ball in such light. Some of these effects seem to me to explain some of your puzzles, but feel welcome to discuss the matter further.

Jagged,

your reply certainly was helpful, but it also presented a more confusing picture, if you don't mind my putting it that way. Please note that whatever I say here is the purest speculation. As should become plain when you read on, I really do not know what is happening in your visual perception.

It is perfectly possible that there is a genetic component that either your daughter inherited, but not your son, or that both inherited, but only one exhibited, a genetic effect called penetrance. The question is whether the physical effect is in your eye, or in your brain. If it is in your eye, then you and your daughter probably have more acute sensitivity to brightness, and more rapid accommodation to changes of brightness. Several kinds of tests might be tried to determine your acuteness of colour discrimination and brightness discrimination and low-light vision. But I leave all such initiatives to you and any interested professionals at your disposal.

If on the other hand the effect is in your brain, then what it suggests to me in my ignorance is that you have the same physical ability to detect flicker as any other healthy person. However, as flicker and persistent visual trails both are confusing, most people have strong innate abilities to filter them out of their conscious perception or suppress them somehow. I get the impression that you and your daughter might be better at perceiving such effects, than filtering them out.

Whether to regard this as more of an asset or a liability, I leave to you. Happily it is at worst no disability and may be an actual advantage under some circumstances.

Personally however I suspect that it is neither one nor the other, but simply a personal quirk.

In either case, the effect is interesting, so do let us know if you discover any more about it.

Go well,

Jon

It might have something to do with the way you move your eyes and where your attention is. If you move your eyes to the right the trail of dots will appear briefly to the left. Your son might not be aware of this because his attention is on the other side. Anyway these flickering leds have been put to use in various diplays where a string of leds projects an image or text. There are clocks, frisbees, wands and even devices you can put in the weel of your bike to display a message. You might want to pick up one of these inexpensive gagets for fun and do some experiments yourself.

Everybody, as you may know, has a blind spot where the are no rod or cone cells present in their eyes. The younger you are the smaller the blind spot. The size of this spot also varies from person to person. 

The reason the LED's appear to flicker is due to the blind spot moving over the light meaning you cannot see the light for that split second. As the light moves back into vision you have completed the flickering cycle. This is the reason that you see the flickering, and maybe your younger son doesn't.