Epstein’s Dollar Bill and What it Doesn’t Prove About the Brain

I hate to pick on poor confused Robert Epstein again, but after thinking about it some more, I’d like to explain why an example in his foolish article doesn’t justify his claims.

Here I quote his example without the accompanying illustrations:

In a classroom exercise I have conducted many times over the years, I begin by recruiting a student to draw a detailed picture of a dollar bill – ‘as detailed as possible’, I say – on the blackboard in front of the room. When the student has finished, I cover the drawing with a sheet of paper, remove a dollar bill from my wallet, tape it to the board, and ask the student to repeat the task. When he or she is done, I remove the cover from the first drawing, and the class comments on the differences.

Because you might never have seen a demonstration like this, or because you might have trouble imagining the outcome, I have asked Jinny Hyun, one of the student interns at the institute where I conduct my research, to make the two drawings. Here is her drawing ‘from memory’ (notice the metaphor):

And here is the drawing she subsequently made with a dollar bill present:

Jinny was as surprised by the outcome as you probably are, but it is typical. As you can see, the drawing made in the absence of the dollar bill is horrible compared with the drawing made from an exemplar, even though Jinny has seen a dollar bill thousands of times.

What is the problem? Don’t we have a ‘representation’ of the dollar bill ‘stored’ in a ‘memory register’ in our brains? Can’t we just ‘retrieve’ it and use it to make our drawing?

Obviously not, and a thousand years of neuroscience will never locate a representation of a dollar bill stored inside the human brain for the simple reason that it is not there to be found.

Now let me explain why Epstein’s example doesn’t even come close to proving what he thinks it does.

First, the average person is not very good at drawing. I am probably much, much worse than the average person in this respect. When I play “pictionary”, for example, people always laugh at my stick figures. Yet, given something to look at and copy, I can do a reasonable job of copying what I see. I, like many people, have trouble converting what I see “in my mind’s eye” to a piece of paper. So it is not at all surprising to me that the students Epstein asks to draw a dollar bill produce the results he displays. His silly experiment says nothing about the brain and what it “stores” at all!

Second, Epstein claims that the brain stores no representation of a dollar bill whatsoever. He is pretty unequivocal about this. So let me suggest another experiment that decisively refutes Epstein’s claim: instead of asking students to draw a dollar bill (an exercise which evidently is mostly about the artistic ability of students), instead give them five different “dollar bills”, four of which have been altered in some fairly obvious respect. For example, one might have a portrait of Jefferson instead of Washington, another might have the “1” in only two corners instead of all four corners, another might have the treasury seal in red instead of the typical green for a federal reserve note, etc. And one of the five is an ordinary bill. Now ask them to pick out which bills are real and which are not. To make it really precise, each student should get just one bill and not be able to see the bills of others.

Here’s what I will bet: students will, with very high probability, be able to distinguish the real dollar bill from the altered ones. I know with certainty that I can do this.

Now, how could one possibly distinguish the real dollar bills from the fake ones if one has no representation of the real one stored in the brain?

And this is not pure speculation: thousands of cashiers every day are tasked with distinguishing real bills from fake ones. Somehow, even though they have no representation of the dollar bill stored in their brain, they manage to do this. Why, it’s magic!


  1. brucegee1962 says

    What Epstein really seems to be trying to prove here is that the brain is not a digital camera. It memorizes things in terms of systems and relationships, not a bitmap.

  2. shallit says

    I think we have to be cautious about universal claims about how the brain represents things, especially when we are still struggling to understand it. Consider, for example, prodigious feats of memory, like the people who memorize pi to many digits (I think the current record is 70,000). Or the people who can multiply 20-digit numbers in their heads. Do you really think these things are achieved by “systems and relationships” alone? Personally, I doubt it.

    • mk says

      “Do you really think these things are achieved by “systems and relationships” alone?”

      Of course.

      “Personally, I doubt it.”


  3. tcmc says

    The cruder drawing in Epstein’s article is a representation of a one dollar bill. The second part of the experiment in which the subject creates an image from the actual bill neither adds to or detracts from the fact.

    • shallit says

      Yes, that’s so, tcmc. But I would add even more is true: the ability of subjects to draw a dollar bill says little about how many bits of representation about the dollar bill they store. Simple information theory, combined with a more elaborate experiment of the type I described, would suffice to estimate how many bits the average person has. Epstein doesn’t seem to understand this at all.

  4. smrnda says

    Your proposed experiment reminds me of some studies in cognitive psychology when they try to figure out what characteristics of things people use to categorize, particularly with children as they begin to understand categories. An example is kids will quickly get that wheels are on vehicles, and not animals.

    Speaking of computers, machine learning often involves (simple explanation) training a computer to categorize things based on features rather than ‘storing’ any complete representation in memory. In fact, to be useful in recognizing items which are not all identical, a computer has to recognize them by key features instead of matching them to an example. So Epstein seems a bit out of date on machine intelligence if he thinks they recognize dollar bills by matching them to a stored picture. If that was the case, than a program for recognizing bills would be easily thwarted simply by defacing George’s face. Epstein should try the following experiment : take a crisp, clean one dollar bill, draw sunglasses on George Washington, and see if a machine will still accept his currency.

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