Never metamer I didn’t like

I saw a great talk this evening by Eero Simoncelli, who gave a broad overview of the research going on in his computational neuroscience lab at NYU. He started with a diagram showing the overlap between three fields: Perception, Engineering and Physiology. The first is the science of what exactly we are able to see, hear, taste, etc. The second helps us create practical tools based on those perceptions. The third dives into the brain itself to understand the mechanism inside us that causes perception to happen the way it does.

The key to studying perception is finding metamers — two or more things that seem the same to our senses even though we know they are different. The classic example of this is how we see colors. In 1853 the great mathematician Hermann Grassmann, working in the field of Perception, showed that everything we see, no matter how rich its color spectrum, is reduced in our perception to just red, green and blue — three colors. Which means that humans can’t see the difference between many objects in the world which actually have wildly different spectra. In a sense, we all suffer from metameric blindness.

By 1931 engineers had codified this knowledge into the CIE color standards that underlie the technology of modern movies, photography, television and computer displays. Yet it wasn’t until 1987 — more a century after Grassmann’s perceptual results — that physiologists in D.A. Baylor’s lab at Stanford were finally able to measure the behavior of a single color receptor cell, showing the actual mechanism inside our bodies that makes all this happen.

It had taken 134 years to go from knowing exactly what our brain is doing, to knowing exactly how our brain is doing it.

This was a great story, but it nearly got waylaid right at the beginning, when a prof in the audience who studies Physiology objected to putting all three fields on an equal footing. “After all,” he said, “Perception is completely subsumed by Physiology”.

Eero said the comment reminded him of that famous New Yorker magazine cover A New Yorker’s View of the World, a cartoon showing that to a New Yorker, the rest of the world seems small and insignificant. Which may or may not be true, but now we know that if you’re Physiologist, the rest of science seems small and insignificant.

After the talk I complimented Eero on a great presentation, and I told him it could also go the other way: Maybe Physiology is completely subsumed by Perception. After all, without our perception we wouldn’t be able to study anybody’s physiology.

Eero replied, sensibly enough, that both fields are subsumed by Physics.

I was about to point out that to a Creationist, Physics would be subsumed by Engineering. But then I thought better of it.

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