Re: Experiments With Human Subjects

Ira Brodsky (
Mon, 23 Sep 1996 14:52:34 -0600

Robin Hanson wrote:

>>By "objective," I mean that most reasonable people would agree the
>>experiment is fair from the outset. By "repeatable," I mean any
>>disinterested party could recreate the experiment and come up with the
>>same results.
>I'd say these criteria are met by most of the experiments in the
>tradition I'm involved with (experimental economics).

That may be the case -- it would be more convincing if you provided some

And would you claim the same is true for most experiments in sociology and
political science?

>>Nope, there is plenty of experimentation in astronomy and geology. Didn't
>>astronomers prove that gravity can bend light waves through an experiment?
>Um, no.

Um, Albert Einstein predicted what was later confirmed:

"Since the fixed stars in the parts of the sky near the sun become visible
during a total eclipse, it is possible to check this theoretical conclusion
[a ray of light coming from a fixed star and just grazing the border of the
sun will be deflected by 0.83 seconds of an arc] by experiment."

>From one of Einstein's papers as quoted in "Einstein: His Life and Times"
by Philipp Frank (Alfred A. Knopf, 1972, New York)

>>In the physical sciences, you can usually test one variable at a time. I
>>don't dispute your claim that often you need to vary more than one thing at
>>a time. The point is you shouldn't start doing that until after you have a
>>firm understanding (verified through experimentation) of what happens when
>>you vary each thing alone.
>>The problem with the social sciences is that there are external forces
>>varying many things *all* of the time. It's virtually impossible to
>>isolate any single factor. For example, how do you design a rigorous
>>experiment to determine whether giving welfare to unwed, teenage mothers
>>will reduce, increase, or have no impact on criminal activity among their
>>children when they grow up?
>You can bring a small number of people into a lab and run an
>experiment on them, and then do it again tommorow and get similar
>results. You can also vary just one aspect of your experiment.

Your first statement may be true for psychology and microeconomics. But is
it true for sociology, political science, and macroeconomics?

As to your second statement, it is certainly true *you* can vary just one
aspect of your experiment. What I am doubting is whether you can reliably
prevent *other* aspects from being varied.

> Of course the new people are different, and even the same
>people would be in different moods, etc. But you're going to say you
>can't do social science because of that, you'll have to dump medical
>science too. Same people, same variance, just asking different questions.

Well, medicine is really a mixture of art and science. Some medical
research is based purely on statistical correlation, while some is based on
cause and effect. But note that most medical research relies on objective
measurements (e.g., size of a tumor, number of white blood cells per CC,
etc.). I would think (but I could be wrong) most social science
experiments on human subjects conducted in a lab rely primarily on what the
subjects say.

>How do you run a rigorous experiment to say what any specific welfare
>bill would do in any specific state? Maybe you can't. But that
>doesn't mean you can't do other things.

We agree.

Ira Brodsky
Datacomm Research Company
Wilmette, Illinois