Happy Fechner Day!

158 years ago today, Gustav Theodor Fechner awoke from a dream which would change his life, and the course of science itself. In his dream, Fechner had discovered the key to studying sensation and perception, the method to measure the mind itself. Of course we cannot simply turn up some switch and increase your awareness, or your sensitivity, or anything about your experience of the world; prior to Fechner's dream, the only way to study your thoughts was... to think about them. Introspection, essentially. It could not be systematically controlled-indeed, the very thought of controlling the mind, that non-physical part of Descartes dualistic view of Man, was ludicrous.

But Fechner found a method that, in hindsight, was simplicity itself. He would vary the external stimulus systematically, and an observer would report whether a perceptual change was noticed. Can you tell the difference in brightness between this light and this one? Can you tell a difference in saltiness between this solution and this one? Can you tell a difference in weight between this cylinder and this one? By reducing the subject's responses to a simple choice, and varying stimulus materials, Fechner could measure sensitivity and bias separately, and could determine both absolute thresholds (the dimmest light, quietest sound, lightest weight, that one can detect 50% of the time) and difference thresholds (how much brighter, louder, heavier, must a stimulus be in order for that difference to be detected) for a number of different sensations and stimuli.

And he found that our perceptions are describable by mathematical equations--initially a simple linear function (Weber's Law), improved to a logarithmic function (Fechner's Law), suggesting that just maybe our minds are not working under separate and distinct rules than our bodies. Fechner's work laid the groundwork for the science of Psychophysics, and pretty much all of experimental Psychology owes a debt to his methodology.

For this Fechner Day, I am re-posting a portion of an older post, from last February. You will see why.

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Parenthetically, I note with sheer joy the fact that the paper cites Fechner (1877). And it is relevant. How cool do you have to be, to have your work cited 131 years after you wrote it? As cool as Fechner, that's how cool. Fechner more-or-less invented the science of psychophysics, managing to capture sensation and perception scientifically for the first time. And here he is, cited in a 2008 paper. On machines tasting espresso.

On second thought, that might be my problem right there. I am still impressed by Fechner, and I live in a world where machines can meaningfully taste coffee. Food... or espresso... for thought.


I have a machine to smell my coffee,
To see if it’s any good;
I asked it to make me the perfect cup,
But I think it misunderstood—
It analyzed alkaloids, sampled aromas,
Tried seventeen samples of beans,
Then told me I clearly had no taste at all:
I never was good with machines.

My pre-owned car has an onboard computer—
It measures my driving, you see.
I guess I don’t drive like the previous owner;
My car likes him better than me.
It spits out a spreadsheet of technical numbers—
I don’t know what much of it means,
Except that my car thinks it’s better without me:
I never was good with machines.

Of course, at my office, I have a computer—
The one I am using right now;
It laughs at my grammar and sneers at my spelling,
Although I’m not really sure how.
Just one tiny part of a cubicle farm
Where we’re packed like so many sardines—
Do we use computers, or do they use us?
I never was good with machines.

I’m worried that someday my household appliances,
Sitting at home on my shelves,
Finally realize there’s nothing I offer
That they can’t do better themselves.
They make better coffee, they get better mileage,
Their words rarely stink up their screens—
And I’ll be left out in the cold and the dark:
I never was good with machines.