Is seeing something that just happens to you when light hits your retina, or is it a mental process?  In two books I’ve read recently scientists describe what it’s like to see things, and they describe it more as an art than a simple sensory function.

The first is William Herschel, a self-taught astronomer from the late eighteenth century.  He made his own telescopes and became the most skillful astronomer of his generation.  Working together with his sister Caroline, he discovered the planet Uranus and lots of other things.

He described his “art of seeing” like this: 

“The eye is one of the most extraordinary Organs...I remember a time when I could not see with a power beyond 200, with the same instrument which now gives me 460 so distinct that in fine weather I can wish for nothing more.”  So visual images didn’t simply fall on the eye like an exposure on film, the eye  interpreted what it saw.  He had to learn to see, and over time became more skillful at it [1].

His son, John Herschel also became an eminent astronomer, and after trying to show something to one of his friends commented, “An object is frequently not seen from not knowing how to see it, rather than from any deficit in the organ of vision...I will instruct you how to seem them” [2].

Another example is Barbara McClintock, a geneticist whose career spanned the 1930s to the 1980s.  She made a name for herself very early in her career for being able to see corn chromosomes under the microscope better than anyone else, and by connecting genetic studies of corn with cytological studies (that is, looking at corn cells under the microscope).  Her work clarified the fact that the things geneticists had observed about the way traits are inherited is based on what physically happens to chromosomes.

After her success with corn, a fellow scientist asked for help with the organism he was working on - Neurospora, or bread mold.  His group had success in studying the genetics of Neurospora, but their work was hindered by the fact that no one could see its chromosomes under the microscope.  So they asked McClintock to help.  She spent three days looking, but got nowhere.  So she realized she had to “do something” with herself, and went for a walk.  She sat on a bench under some eucalyptus trees at Stanford for a while, then, “Suddenly I jumped up, I couldn’t wait to get back to the laboratory.  I knew I was going to solve it - everything was going to be all right.” 

And within 5 days she’d identified all seven Neurospora chromosomes and followed them through cell divisions.  How did she do it?  She said, “I found that the more I worked with [the chromosomes] the bigger and bigger they got, and when I was really working with them I wasn’t outside, I was down there.  I was part of the system.   I was right down there with parts of the chromosomes - actually everything was there.  It surprised me because I actually felt as if I were right down there and these were my friends” [3]. 

I never had an epiphany like that while I was doing research in grad school.  In fact, from what I’ve read, I think things like that are extremely rare (the story of Newton thinking of gravity when he saw an apple fall is apocryphal).  I also don’t think I ever acquired exceptional skills as a microscopist, although I spent a lot of time looking through microscopes.  But there is a certain amount of skill needed before you can look through an eyepiece and get any work done on a microscope.  So I appreciate what the Herschels and McClintock said.

I can think of other examples where knowing what you are looking for helps you see more than someone with an inexperienced eye - seeing camouflaged animals, cracking secret codes, or detecting fake pieces of art, for instance.  But people also sometimes see things that aren’t really there.  For example Herschel was convinced he saw inhabitants on the moon, and McClintock made an even bigger mistake.  She observed that certain kinds of genes in corn are inherited in an unconventional way (they were transposable, or “jumping” genes), and became convinced that corn used these genes to control development.  She was wrong about that, but believed it to the end, even when she was awarded the Nobel Prize for discovering transposable genes and everyone else in the field at the time had totally rejected her interpretation of them.  The Nobel Prize was in a way a repudiation of her ideas, and she knew it [4].

I guess there’s a bit of a cautionary tale here.  We have to be able use our experience and skills to interpret what we see, but it’s possible to become so confident in our abilities to perceive things correctly that we can’t tell when we’re wrong.  Something to be aware of, I think.

1. 1.The Age of Wonder: How the Romantic Generation Discovered the 
   

    Beauty and Terror of Science by Richard Holmes, page 116.

2. 2.Ibid, page 440.
   

3. 3.A Feeling for the Organism: the Life and Work of Barbara McClintock by Evelyn Fox Keller, page 117.
   

4. 4.The Tangled Field by Nathaniel Comfort, page 11.