I am not I: The fastest biochemical event and the speed of light, or, The Bathroom Mirror phenomenon

Stumbling to my bathroom in the morning and surveying my beard in the mirror one foot away from me, it occurred to me that who I was seeing was actually the person who I was 23.6 nanoseconds ago: one light beam out, one trip back.

I am considering my face and the mirror perfect reflectors. Also, luckily, I do not shave in a vacuum. Any adjustments to these figures would be greatly appreciated.

After I recovered from this too-early-in-the-morning mind fuck, I began to think in what ways I had changed in that interval.

Submitted for your approval and comments.


Well, you got older during that interval.

Unless your bathroom mirror’s made of some bizarre metamaterial, it shouldn’t be taking that long. 1 light-ns is 30 cm, or about a foot, as Admiral Hopper was fond of pointing out. But there is the fact that it takes time to process the image in your brain, so when you “see” something it’s even older.

Consider also that almost everything you see of yourself externally — your eyes being the main exception — is dead.

That may be true of you. It isn’t true of regular human beings.

You don’t witness *any *event at the same time it happens. Whether it’s a supernova a million light years away, or an apple falling off a table in front of you - you’re experiencing history only.

The outer layer of the epidermis - the stratum corneum is composed of dead cells, is it not?

Perhaps you mean that we can see through it to living structures below? (it really would help if you elaborated, in that case)

The actual dead layer of the skin is only microns thick, and the material is is highly translucent, making it effectively perfectly transparent. Saying that what you see of yourself externally is dead exept for the eys is simply not true. Either you can’t see living tissue in your eyes either, because of the transparent film of tears, or else you can see living tissue perfectly clearly everywhere in the body.

Your brain and nervous system can’t process data instantly. You can add somewhere around 50 ms of signal delay for your eyes to get the data to the brain and the brain to interpret it. Your brain is also taking the data from your eyes and combining it with memories already in your brain to produce what you “see” so what you see isn’t even reality, completely.


I’ve got to go put my pants on!

If we assume you stand half a meter away from your mirror, the image you see back will be from 3.33564 nanoseconds ago. Perhaps, though, you have an unusually large bathroom.

Or just slow light.

Yeah, I know I’m not at my best before I’ve had caffeine. I don’t know how much I’d need if I were bending time and space to my whims.

Any visible part of your body has been replaced several times since you were a child. The face you see in the mirror now is not the face you remember from a few years ago.

Perception is mostly anticipatory. We experience most things fractionally before they happen, not fractionally after. If that was not true, nobody would be able to catch a ball or get out of the way of an onrushing train. Just occasionally, what actually happens is different from what our brains anticipate and we are disconcerted, or fumble something, and our brains adjust their expectations in order to have a better chance of anticipating correctly next time.

The OP shows a fundamental (but very common) misunderstanding of how visual (and other) perception works. It is not a one-way flow of information from what is out there into your brain. It is a constant back and forth between your brain seeking out information from the environment (via strategies that include moving your eyes, several times a second, in order to pick up useful information from where the brain expects to find it) and the information out there, available to be picked up, in the structure of the ambient light.

And in my case, I’m mostly dead on the inside.

Incidentally, if perception were a one way flow if visual information starting from the perceived object and flowing into some center of experience in the brain, then the delay would be much greater than that arising from the time that light takes to travel from your mirror to your eyes. It would be more on the order of several tenths of a second, rather than nanoseconds. The speed that electrochemical impulses travel down the optic nerve, and through all the other neurons that would presumably have to be involved, the speed of information transmission (via diffusing chemicals) across the synapses between neurons, and the speed at which the receptors in the retina convert incoming light into electrochemical nerve impulses, are all very, very much slower than the speed of light. To repeat, you would never be able to catch a ball, or do anything else that requires even moderately fast reaction to external events, unless perception were mostly anticipatory rather than merely reactive.


Reaction time to random stimuli is well under a second, including not only visual processing but actual voluntary muscle reaction. It’s physically impossible for your brain to anticipate a random event and perceive it before it happens. You can catch a ball because your brain projects its path, not because you see it coming before it’s actually coming.

Which is caused by cheap light bulbs. You need quality bulbs to get the full speed light.

For the OP, there are a few things you can do to change the interval. Step closer to the mirror is one way, of course, or you can do like I do and start shaving a few nanoseconds before you were originally planning to.

That’s why I use Neutrino bulbs - the light is emtted before I switch them on (allowing me to change my mind - not turn them on - and thus save money)

I didn’t say random stimuli, most stimuli do not occur at random. Most perceptible events (including seeing yourself in a mirror when you look in a mirror) follow in an orderly, predictable way from the perceptible events that preceded them. Most events that we percieve are anticipated, a few of them, random events, are not, which is precisely why we often can’t react quickly enough to them. And no, you don’t see the ball is coming before it is coming (although you may well anticipate that it will if say, you are a fielder and are paying attention to the game), but you see where it is going to be when it is coming, well before it gets there, and that prediction/projection is what enables you to catch it. The finite speed of light is no impediment.

You want citations that vision is anticipatory, do you? Have at it:

Aloimonos, Y. (Ed.). (1993). Active Perception. Hillsdale, NJ: Erlbaum

Ballard, D.H. (1991). Animate Vision, Artificial Intelligence, 48, 57-86.

Blake, A., & Yuille, A. (Eds.). (1992). Active Vision. Cambridge, MA: MIT Press.

Bressler, S.L., Tang, W., Sylvester, C.M., Shulman, G.L., & Corbetta, M. (2008). Top-Down Control of Human Visual Cortex by Frontal and Parietal Cortex in Anticipatory Visual Spatial Attention. Journal of Neuroscience (28 #40) 10056-10061.

Castelhano, M.S., Mack, M.L., & Henderson, J.M. (2009). Viewing Task Influences Eye Movement Control During Active Scene Perception. Journal of Vision, 9(3):6, 1-15: Viewing task influences eye movement control during active scene perception | JOV | ARVO Journals

Findlay, J.M. & Gilchrist, I.D. (2003). Active Vision: The Psychology of Looking and Seeing. Oxford: Oxford University Press.

Hayhoe, M. (2000). Vision Using Routines: A Functional Account of Vision. Visual Cognition (7) 43-64.

Kveraga, K., Ghuman, A.S., & Bar M. (2007). Top-down predictions in the cognitive brain. Brain and Cognition, 65(#2) 145-168. Online: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2099308/

Land M.F. & McLeod P. (2000). From eye movements to actions: How batsmen hit the ball. Nature Neuroscience, 3, 1340-1345.

Landy, M. S., Maloney, L. T., & Pavel, M. (Eds.). (1996). Exploratory Vision: The Active Eye. New York: Springer-Verlag.

Li, W., Piëch, V., & Gilbert, C.D. (2004). Perceptual Learning and Top-down Influences in Primary Visual Cortex, Nature Neuroscience, 7 #6, 651-657.

Liu, T., Larsson, J., & Carrasco, M. (2007). Feature-based attention modulates orientation-selective responses in human visual cortex. Neuron, 55, 313-323.

Munneke, J., Heslenfeld, D.J., & Theeuwes, J. (2008). Directing Attention to a Location in Space Results in Retinotopic Activation in Primary Visual Cortex. Brain Research (1222) 184-191.

Neisser, U. (1976). Cognition and Reality. San Francisco: Freeman.

Noë, A. (2004). Action in Perception. Cambridge, MA: MIT Press.

O’Regan, J.K. & Noë A. (2001). A Sensorimotor Account of Vision and Visual Consciousness, Behavioral and Brain Sciences, 24, 939-1031. (Online: http://nivea.psycho.univ-paris5.fr/OREGAN-NOE-BBS/ORegan;Noe.BBS.pdf)

O’Regan J.K. Myin E. Noe A. (2005.) Skill, corporality and alerting capacity in an account of sensory consciousness. Progress in Brain Research (150) 55-68.

Thomas, N.J.T. (1999). Are Theories of Imagery Theories of Imagination? An Active Perception Approach to Conscious Mental Content. Cognitive Science, 23, (1999) 207-245: http://www.imagery-imagination.com/im-im/im-im.htm

Roelfsema, P.R., Lamme, V.A.F., & Spekreijse H. (2000). The Implementation of Visual Routines. Vision Research (40) 1385–1411.

Rothkopf, C.A., Ballard, D.H., & Hayhoe, M.H. (2007). Task and Context Determine Where You Look. Journal of Vision (7 #14:16) 1-20. Online, open access publication: Task and context determine where you look | JOV | ARVO Journals

Sirotin, Y.B. & Das, A. (2009). Anticipatory Haemodynamic Signals in Sensory Cortex Not Predicted by Local Neuronal Activity. Nature (457 #7228) 475-479.