The Sense Of Being Stared At

There’s been something a minor discussion of Rupert Sheldrake’s ideas going on in the comments, so it was on my mind when I sat down with a beer in a sunny pub garden today, lit a cigarette, and started vaguely thinking about The Sense of Being Stared At.

There are two main reasons for the conventional dismissal of the sense of being stared at. First, it is classified as ‘paranormal’. It is normal in the sense that most people have experienced it for themselves. But it falls foul of the general taboo against psychic phenomena. For generations, educated people have dismissed it as a superstition.

Second, it conflicts with the orthodox scientific theory of vision, first published in 1604 by Johannes Kepler (1571–1630), best known for his discoveries in astronomy. Kepler’s was an ‘intromission’ theory, according to which light came into the eyes, but nothing went out of them. Vision was not in the outer world where it seemed to be, but inside the head…

On Kepler’s theory, the sense of being stared at ought not to exist. Hence it has generally been ignored by scientifically educated people, or dismissed as a superstition.

I’d thought about it before. But this afternoon I suddenly realised that we always think about eyes solely as recipients of external light, with the light going from outside the eye to inside the eye and onto the retina. Never mind Kepler, we don’t think of light going the other way, with the eye acting like a cine projector, only because we don’t have any light source inside our eyes to shine out onto the world outside.

Except that we do have such a light source inside our eyes.

It’s just that it’s not a visible light source. It’s an infra-red light source. And this infra-red light source is the warm retina at the back of our eyes. This is radiating infra-red light back out through the eye’s lens onto the outside world. Assuming the retina is at the same 37°C temperature as the body tissue surrounding it, this warm retina will be radiating heat out onto the cooler outside world (about 17° C in the pub garden). So while our eyes are receiving visible light from the outside world, they should also be emitting IR light onto the outside world. But it won’t be very much.

In fact, we can estimate roughly how much power our eyes are emitting by using the Stefan-Boltzmann equation, q = σT4A, where σ is the Stefan-Boltzmann constant 5.6703 10-8 W/m2K4, T is the temperature difference between the eye and its surroundings ( 20° K), and A is the area of the eye retina. The human eye has a diameter of 24 mm, and the area of the retina is given as 1,094 square mm or 0.001094 m2. So power q = 9.92 10-6 watts. And given two eyes, 19.8 10-6 watts, or 19.8 microwatts.

Could anyone possibly sense something as small as 20 microwatts?

Well, if (and it’s a very big if) those 20 microwatts can be focused on one single point on somebody’s skin for a period of several seconds or minutes while they are being stared at, there will be a very small localised temperature gain. If the single point was a single human cell, for example a fibroblast cell with a volume of 2000 μm3, a density of 1000 kg/m3 (water), and a specific heat of 4.183 kJ/kg °K (water), it will rise 1.25°C after half a minute of receiving a 20 microwatt heat input.

And maybe somebody could feel that, as a burning or pricking sensation or something.

That’s the radiative physics of it, to the best of my knowledge. And there’s nothing ‘paranormal’ about it.

It might be possible to devise an empirical physical experiment to check this. One experiment might be to have a frozen droplet of water (or a temperature sensor) surrounded by 10 or 20 people who keep their eyes fixed on it for 10 minutes, and see whether its temperature rises. Another experiment might be to stare into an IR camera, although I somehow doubt they can register microwatts.

Rather more speculatively, it might be wondered whether retinal temperatures rise when someone is staring very intently at something, and their retinas are working harder, just as body temperatures rise when muscular work is being done. If so, retinal IR emissions would be correspondingly high. Maybe there’s something to the lyrics of Lana del Rey’s Blue Jeans?

Blue jeans, white shirt.
Walked into the room, you know you made my eyes burn

Even more speculatively, when rock stars (like Lana del Rey) are ‘bathed in adulation’ in front of thousands of rapt, adoring fans, maybe they’re getting a storm blast of infra-red from their massed fans’ eyes.

Cats’ eyes have a reflective layer – the tapetum lucidum – behind the retina, which means that any incoming light that passes through the retina is reflected back through the retina a second time, effectively doubling its intensity. But this same reflective layer would act to double the intensity of infra-red light being radiated by the eyes. Might cats be able to hunt in complete pitch darkness, using their eyes as searchlights?

Anyway, the microwatt power levels of infra-red eye emissions look as though they’re probably far too low for anyone to ever notice them. But given that dogs can detect odours at 1 part in one trillion, maybe some animals can detect radiant heat at microwatt levels when they’re being watched, and be able to tell from what direction. For them it would be like standing in sunshine.


About Frank Davis

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29 Responses to The Sense Of Being Stared At

  1. At first I thought, well, the whole body will be radiating that heat, so why would we register something different from the retina.

    But then it occurred to me: our skin is likely much cooler than our core body heat, and our retina is going to be significantly warmer than our skin. Soooo…. your pinpoint radiation is quite possible! And if we saw in the infrared then we’d see those two glowing little hot spots when they were focused on us.

    Now how closely do they have to be aimed? If you and I are standing right next to each other and 3 feet away from a pretty gal, we can easily tell who she’s looking at. But what if she’s 30 feet away? Or 100? At what distance are we unable to tell if someone is staring AT us or is staring at something NEAR us? And at what distance would that retinal heat focus lose such definition? Our “focus circle” if you think about it is a bit smaller than the moon, and the moon is, I believe, a half degree? Am I remembering that correctly?

    So what if someone a hundred feet from us was staring not quite at us but at someone a foot to our side. Our eyes might not be able to pick up that difference, BUT… that hypothetical awareness of the retinal energy might be focused enough for us to know… if indeed we could sense it!

    Heh… ok… enough wild speculation for the day. You DO have interesting ideas Frank!


    • Frank Davis says:

      Our “focus circle” if you think about it is a bit smaller than the moon, and the moon is, I believe, a half degree? Am I remembering that correctly?

      The angular diameter of both sun and moon is about half a degree.

      So what if someone a hundred feet from us was staring not quite at us but at someone a foot to our side. Our eyes might not be able to pick up that difference, BUT… that hypothetical awareness of the retinal energy might be focused enough for us to know… if indeed we could sense it!

      I almost wrote something like that in my piece. Never mind someone staring at the back of your neck, what happens when eyes meet? It’s something that we sense readily every day. And eyes seem to be able to meet at quite long ranges, like maybe up to 100 feet. It makes sense that you can know that someone is looking into your eyes when you’re a few feet away, and looking into their eyes. But I seem to sort of know that someone is looking at me if I can’t see their eyes at all. How does that work? Well, if someone is projecting a beam of IR along the line of sight, then my eyes could be picking it up and registering it (except that my retina is at the same temperature as theirs).

      Anyway, even if I’ve got the radiative physics right, there are several big problems with this idea. One of these is that eyeballs are full of vitreous humour, which is 98% water, and water is quite strongly absorptive of IR. Same for the cornea. The IR beam (with a peak wavelength of 9.66 microns) would never get through it.

      And there are problems with the optics. When we focus on some distant object, I believe the eye simply changes the focal length of the eye lens so that objects at that distance are brought into focus on the retina. It doesn’t mean that all the light coming into an eye is coming from (or going towards) the object on which we are focusing our attention. We still have peripheral vision. So even if the IR leaving the retina manages to get through the vitrous humour in the eye, it would then spray out in all directions, just like the light coming in. The narrow beam would be coming from the central field of vision, where most of our eye’s rod and cone receptors are located.

      It seemed like a good idea when I’d had a couple of beers (as things always tend to), but I’m getting increasingly doubtful about it.

      • click clock ... says:

      • “It seemed like a good idea when I’d had a couple of beers (as things always tend to), but I’m getting increasingly doubtful about it.”

        Dr. Michaellious would prescribe a few more beers normally, but in your case I believe you may have built up a drug resistance. As a result I will refer you to my Colleague, Dr. PFA (Perambulatory Ferrous Appendage) who will discuss further treatment options with stronger, more highly distilled medications.

        Love Dr. Lilith btw Roobee ‘n Click! Now I’m off to find my WD-40!


  2. junican says:

    Richard Feidmann (?), in his ‘lectures on physics’, suggested that light is not reflected. That when light hits a surface, all of it is absorbed. What happens then is that the surface, depending upon its composition, emits light as a consequence of the prior absorption. Thus, a surface painted with red pigment, will absorb all the light which hits it, but emit only red light as a consequence. Thus, it is entirely possible for eyes to emit ‘light’ of any kind.
    Nice though your calculations are, Frank, it is hardly likely that person would be conscious of such minute differences among all the ‘noise’ of variations in infra red, visible light and ultra violet which occur instant by instant. For example, it is hardly likely that a person will stare at a precise cell for half a minute.
    If it is true that people can be conscious of being stared at, and there are many reports of such phenomena, then there must be other perceptions at work. There again, I have never had a young, fit woman turn round and ask me why I am staring at her bum – never, never, ever, ever.
    It seems more likely that those people who claim that they are conscious of someone staring at them do so because they expect someone to be staring at them, and look for someone staring at them.
    To me, what is more interesting is that people sometimes experience a sense of unease – that something awful is about to happen, or even that something nice is about to happen. The classic was that there were some people who were uneasy before the tsunami which hit Thailand. There were visual prompts, such as the sea retreating.
    But it may well be true that we have built-in awarenesses of which we are not consciously aware due to evolution. How do we know that variations in light levels, barometric pressure differences and the rapidity of changes therein, do not impinge upon our subconscious?

    Fun, is it not?

    • Lepercolonist says:

      That would be Richard Feynman. Junican, you made me break out in laughter about the young, fit woman.

    • Frank Davis says:

      I have never had a young, fit woman turn round and ask me why I am staring at her bum – never, never, ever, ever.

      Perhaps they’re just used to having burning bottoms. And when they get home, about the first thing they do is to dunk their derrières in a tub of ice water.

      But how should I know. We’ll have to ask the girls.

  3. Lepercolonist says:

    I learn more real science here than all those bogus anti-smoker tracts. I do not remember Sheldrake touching on this retinal microwattage. Fascinating science. Interesting that women have a stronger sense of being stared at but men have a stronger influence from their stares.

  4. waltc says:

    Googling “sense of being stared at” and “study” I got too many dry entries to bother with but I suppose we could all do an experiment. Next time you’re on a bus or any place where people are stationary, try staring at someone from behind or from an oblique or side angle and see what happens. Do they turn and look back at you?

    I believe that in some way we “see” with more than our eyes or maybe it’s just that our brains don’t consciously register everything our eyes see. Case in point: there’s a public high school a few blocks from my house that I pass almost daily. and always passed w/o a thought. One day x yrs ago as I was about to cross the side street that would lead me to pass the school, I had one of those odd inchoate and not quite mentally articulated senses of danger–something so strong at a gut level that it mindlessly impelled me to cross the wide avenue at that corner instead of the side street. I was halfway across the avenue when gunshots went off from the school entrance– the entrance itself being about an eighth ways down the side street. I was not conscious of having “seen” anything that would even vaguely have predicted this. But… What did I see? Or how did I sense this?

    • waltc says:

      I should add that the shots were aimed towards the corner. No one was hit but people were screaming and taking off like a flock of birds.

      • Rose says:

        I’m not convinced about Frank’s eye theory, Walt, but I am convinced that we all have internal radar, in some more acute than others. Were you picking up the gunman’s thoughts in some unfocused way, could it be a bystander’s apprehension being broadcast who could actually see what you could not?

        Long ago , we would all have needed to sense the hidden predator in the undergrowth and be ready to run, fight or hide. Get caught unwares and you’d be lunch.

        Now how it works I wouldn’t like to say, but as we are all a pulsating mass of electrical signals I can’t see why those signals shouldn’t be projected outside the body routinely or even consciously.

        I was about to cross the side street

        So you would already be on the alert.

        • waltc says:

          I like your idea that I possibly saw a “bystander’s apprehension” . Dogs can smell fear and while I don’t claim to have an extraordinarily acute sense of smell, I may have caught the vibes of other people’s fear. There must have been something or other in the air and, yes, why not? something that I perceived on a primitive or even animal level. But it must have been something elusively tangible; not paranormal.

        • roobeedoo2 says:

          WaltC, could it have been second-hand smoke?

        • Rose says:

          “Paranormal events are phenomena described in popular culture, folklore and other non-scientific bodies of knowledge, whose existence within these contexts is described to lie beyond normal experience or scientific explanation”

          Paranormal or not, thank goodness whatever it was, was working well that day.

  5. Zaphod says:

    The human eye is unusual, I think. The white makes a noticeable circle when someone is looking directly at you, especially if they’re interested and “wide-eyed”.

    This very important social cue can be unconsciously spotted when your own eye is doing that constant automatic scanning (saccades?) that we are unaware of.

    It won’t work if the starer is behind you. But it will in your peripheral vision. It’s not paranormal.

    The staring tactic is regularly used for mating and aggression.
    A stares at B. B looks round.
    If B doesn’t look round, A knows that B doesn’t want to engage.

    We all know it works. We’re just not aware that we know.

  6. Furor Teutonicus says:

    XX Another experiment might be to stare into an IR camera, although I somehow doubt they can register microwatts.XX

    Is that not exactly what the Hubble does? Or any other space exploration sattelite? Surely the red shift in stars many billions of light years away, can only be measured in these frequencys?

  7. woodsy42 says:

    I thought that under the recent findings of physics the world does not exist except when we are present to perceive it? In that case we are already approaching the realm of the ‘paranormal’. Maybe if you are being stared at you become more solidly into existence than you were when nobody was taking much notice of you?

    • roobeedoo2 says:

      Ah but that investigation was paid for by ‘Big Tobacco’ …

      • beobrigitte says:

        Naw. Big Tobacco Control made sure only tobacco control&friends funded investigations:
        1. destroyed independent, and with that all valuable, research
        2. lobbied it’s way into gullible governments
        when it comes to the tobacco industry.

        Politicians really can’t be bright people. NONE of them made the effort to look into who funds what…..

        • roobeedoo2 says:

          BB, Politicians are too enamoured with the Prissy Missys at the WHO …

          Yikes Clicky! Say, don’t you think they look tired?

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