Richard Feynman - CARGO CULT SCIENCE

from the Caltech commencement address given in 1974.

During the Middle Ages there were all kinds
of crazy ideas, such
as that a piece of rhinocer
os horn would increase potency. Then a
method was
discovered for separating the ideas--which was to try
one to see if it worked, and if it didn't wo
rk, to eliminate it.
This method became organized
, of course, into science. And it
developed very
well, so that we are now in the scientific age. It
is such a scientific age, in fact that we have d
ifficulty in
understanding how witch doctors coul
d ever have existed, when
nothing that they propo
sed ever really worked--or very little of
it did.

But even today I meet lots of people who soon
er or later get me
into a conversation about UFOS
, or astrology, or some form of
mysticism, expand
ed consciousness, new types of awareness, ESP, and
so forth. And I've concluded that it's not a sci
entific world.

Most people believe so many won
derful things that I decided to
investigate why t
hey did. And what has been referred to as my
osity for investigation has landed me in a difficulty where I
found so much junk that I'm overwhelm
ed. First I started out by
investigating various
ideas of mysticism, and mystic experiences.
I wen
t into isolation tanks and got many hours of hallucinations,
so I know something about that. Then I
went to Esalen, which is a
hotbed of this kind o
f thought (it's a wonderful place; you should
visit there). Then I became overwhelmed. I didn't realize how
much there was.

At Esalen there a
re some large baths fed by hot springs situated
n a ledge about thirty feet above the ocean. One of my most
pleasurable experiences has been to sit
in one of those baths and
watch the waves crashi
ng onto the rocky shore below, to gaze into
the c
lear blue sky above, and to study a beautiful nude as she
quietly appears and settles into the bath
with me.

One time I sat down in a bath where
there was a beautiful girl
sitting with a guy who
didn't seem to know her. Right away I began
king, "Gee! How am I gonna get started talking to this
beautiful nude babe?"

I'm trying to figu
re out what to say, when the guy says to her,
, uh, studying massage. Could I practice on you?"

"Sure," she says. They get out of the bath and
she lies down on a
massage table nearby.

I t
hink to myself, "What a nifty line! I can never think of
anything like that!" He starts to rub her
big toe. "I think I feel
it, "he says. "I feel a
kind of dent--is that the pituitary?"

I blurt
out, "You're a helluva long way from the pituitary, man!"

They looked at me, horrified--I had bl
own my cover--and said, "It's

quickly closed my eyes and appeared to be meditating.

That's just an example of the kind of thi
ngs that overwhelm me. I
also looked into extrase
nsory perception and PSI phenomena, and the
t craze there was Uri Geller, a man who is supposed to be able
to bend keys by rubbing them with hi
s finger. So I went to his
hotel room, on his inv
itation, to see a demonstration of both
ng and bending keys. He didn't do any mindreading that
succeeded; nobody can read my mind, I guess.
And my boy held a key
and Geller rubbed it, and
nothing happened. Then he told us it
works better
under water, and so you can picture all of us standing
in the bathroom with the water turned on an
d the key under it, and
him rubbing the key with
his finger. Nothing happened. So I was
unable to
investigate that phenomenon.

But then I began
to think, what else is there that we believe? (And
I thought then about the witch doctors, and how
easy it would have
been to cheek on them by notic
ing that nothing really worked.) So
I found thing
s that even more people believe, such as that we have
some knowledge of how to educate. There are b
ig schools of reading
methods and mathematics met
hods, and so forth, but if you notice,
you'll see
the reading scores keep going down--or hardly going up
in spite of the fact that we continually us
e these same people to
improve the methods. There
's a witch doctor remedy that doesn't
work. It ou
ght to be looked into; how do they know that their
method should work? Another example is how to tr
eat criminals. We
obviously have made no progress
--lots of theory, but no progress--
in decreasing
the amount of crime by the method that we use to
handle criminals.

Yet these things are said t
o be scientific. We study them. And I
think ordin
ary people with commonsense ideas are intimidated by
this pseudoscience. A teacher who has some goo
d idea of how to
teach her children to read is fo
rced by the school system to do it
some other way
--or is even fooled by the school system into
nking that her method is not necessarily a good one. Or a parent
of bad boys, after disciplining th
em in one way or another, feels
guilty for the re
st of her life because she didn't do "the right
hing," according to the experts.

So we really
ought to look into theories that don't work, and
science that isn't science.

I think the educat
ional and psychological studies I mentioned are
xamples of what I would like to call cargo cult science. In the
South Seas there is a cargo cult of
people. During the war they saw
airplanes land w
ith lots of good materials, and they want the same
thing to happen now. So they've arranged to imit
ate things like
runways, to put fires along the s
ides of the runways, to make a
wooden hut for a m
an to sit in, with two wooden pieces on his head
like headphones and bars of bamboo sticking out like antennas--he's
the controller--and they wait f
or the airplanes to land. They're
doing everythin
g right. The form is perfect. It looks exactly the
way it looked before. But it doesn't work. No ai
rplanes land. So
I call these things cargo cult s
cience, because they follow all the
apparent prec
epts and forms of scientific investigation, but
hey're missing something essential, because the planes don't land.

Now it behooves me, of course
, to tell you what they're missing.
But it would
be just about as difficult to explain to the South Sea
Islanders how they have to arrange things so
that they get some
wealth in their system. It is
not something simple like telling
them how to im
prove the shapes of the earphones. But there is one
feature I notice that is generally missing in c
argo cult science.
That is the idea that we all h
ope you have learned in studying
science in schoo
l--we never explicitly say what this is, but just
hope that you catch on by all the examples of sci
investigation. It is interesting, therefo
re, to bring it out now
and speak of it explicitl
y. It's a kind of scientific integrity,
a princip
le of scientific thought that corresponds to a kind of
utter honesty--a kind of leaning over backwa
rds. For example, if
you're doing an experiment,
you should report everything that you
think might
make it invalid--not only what you think is right about
it: other causes that could possibly expla
in your results; and
things you thought of that y
ou've eliminated by some other
experiment, and ho
w they worked--to make sure the other fellow can
tell they have been eliminated.

Details that c
ould throw doubt on your interpretation must be
iven, if you know them. You must do the best you can--if you know
anything at all wrong, or possibl
y wrong--to explain it. If you
make a theory, for
example, and advertise it, or put it out, then
ou must also put down all the facts that disagree with it, as well
as those that agree with it. The
re is also a more subtle problem.
When you have p
ut a lot of ideas together to make an elaborate
heory, you want to make sure, when explaining what it fits, that
those things it fits are not just
the things that gave you the idea
for the theory;
but that the finished theory makes something else
come out right, in addition.

In summary, the
idea is to try to give all of the information to
help others to judge the value of your contributi
on; not just the
information that leads to judgme
nt in one particular direction or

e easiest way to explain this idea is to contrast it, for
example, with advertising. Last night I h
eard that Wesson oil
doesn't soak through food. W
ell, that's true. It's not dishonest;
but the thi
ng I'm talking about is not just a matter of not being
dishonest, it's a matter of scientific integ
rity, which is another
level. The fact that shoul
d be added to that advertising statement
is that
no oils soak through food, if operated at a certain
temperature. If operated at another temperature
, they all will--
including Wesson oil. So it's t
he implication which has been
conveyed, not the f
act, which is true, and the difference is what
have to deal with.

We've learned from experie
nce that the truth will come out. Other
ters will repeat your experiment and find out whether you
were wrong or right. Nature's phenomena w
ill agree or they'll
disagree with your theory. A
nd, although you may gain some
temporary fame and
excitement, you will not gain a good reputation
as a scientist if you haven't tried to be very careful in this kind
of work. And it's this type of
integrity, this kind of care not to
fool yourself
, that is missing to a large extent in much of the
research in cargo cult science.

A great deal
of their difficulty is, of course, the difficulty of
the subject and the inapplicability of the sc
ientific method to the
subject. Nevertheless it
should be remarked that this is not the
only diff
iculty. That's why the planes didn't land--but they don't

We have learned a lot from exp
erience about how to handle some of
the ways we f
ool ourselves. One example: Millikan measured the
charge on an electron by an experiment with falli
ng oil drops, and
got an answer which we now know
not to be quite right. It's a
little bit off, be
cause he had the incorrect value for the
y of air. It's interesting to look at the history of
measurements of the charge of the electron, af
ter Millikan. If you
plot them as a function of t
ime, you find that one is a little
bigger than Mi
llikan's, and the next one's a little bit bigger than
that, and the next one's a little bit bigger
than that, until
finally they settle down to a nu
mber which is higher.

Why didn't they discover
that the new number was higher right away?
a thing that scientists are ashamed of--this history--because
it's apparent that people did things
like this: When they got a
number that was too hi
gh above Millikan's, they thought something
be wrong--and they would look for and find a reason why
something might be wrong. When they got a n
umber closer to
Millikan's value they didn't look
so hard. And so they eliminated
the numbers that
were too far off, and did other things like that.
We've learned those tricks nowadays, and now we
don't have that
kind of a disease.

But this l
ong history of learning how not to fool ourselves--of
having utter scientific integrity--is, I'm so
rry to say, something
that we haven't specificall
y included in any particular course that
I know o
f. We just hope you've caught on by osmosis.

he first principle is that you must not fool yourself--and you are
the easiest person to fool. So y
ou have to be very careful about
that. After you'
ve not fooled yourself, it's easy not to fool other
scientists. You just have to be honest in a con
ventional way after

I would like to add
something that's not essential to the science,
ut something I kind of believe, which is that you should not fool
the layman when you're talking as
a scientist. I am not trying to
tell you what to
do about cheating on your wife, or fooling your
girlfriend, or something like that, when you're not trying to be
a scientist, but just trying to be
an ordinary human being. We'll
leave those probl
ems up to you and your rabbi. I'm talking about
specific, extra type of integrity that is not lying, but bending
over backwards to show how you ar
e maybe wrong, that you ought to
have when acting
as a scientist. And this is our responsibility as
scientists, certainly to other scientists, and I
think to laymen.

For example, I was a little
surprised when I was talking to a
friend who was
going to go on the radio. He does work on cosmology
and astronomy, and he wondered how he would exp
lain what the
applications of this work were. "We
ll," I said, "there aren't any."
He said, "Yes, b
ut then we won't get support for more research of
this kind." I think that's kind of dishonest. If
representing yourself as a scientist, then
you should explain to
the layman what you're doi
ng--and if they don't want to support you
under t
hose circumstances, then that's their decision.

One example of the principle is this: If you've
made up your mind
to test a theory, or you want t
o explain some idea, you should
always decide to
publish it whichever way it comes out. If we only
publish results of a certain kind, we can make th
e argument look
good. We must publish both kinds
of results.

I say that's also important in giv
ing certain types of government
advice. Supposing
a senator asked you for advice about whether
lling a hole should be done in his state; and you decide it
would be better in some other state. If
you don't publish such a
result, it seems to me
you're not giving scientific advice. You're
used. If your answer happens to come out in the direction the
government or the politicians like,
they can use it as an argument
in their favor; if
it comes out the other way, they don't publish
t at all. That's not giving scientific advice.

Other kinds of errors are more characteristic of
poor science. When
I was at Cornell, I often talk
ed to the people in the psychology
department. On
e of the students told me she wanted to do an
eriment that went something like this--it had been found by
others that under certain circumstances
, X, rats did something, A.
She was curious as to
whether, if she changed the circumstances to
they would still do A. So her proposal was to do the experiment
under circumstances Y and see if th
ey still did A.

I explained to her that it was
necessary first to repeat in her
laboratory the
experiment of the other person--to do it under
ndition X to see if she could also get result A, and then change
to Y and see if A changed. Then sh
e would know that the real
difference was the thi
ng she thought she had under control.

She was
very delighted with this new idea, and went to her
professor. And his reply was, no, you cannot do
that, because the
experiment has already been don
e and you would be wasting time.
This was in abou
t 1947 or so, and it seems to have been the general
policy then to not try to repeat psychological
experiments, but
only to change the conditions an
d see what happens.

Nowadays there's a certain
danger of the same thing happening, even
in the
famous (?) field of physics. I was shocked to hear of an
experiment done at the big accelerator at
the National Accelerator
Laboratory, where a pers
on used deuterium. In order to compare his
hydrogen results to what might happen with light hydrogen"
he had to use data from someone else's e
xperiment on light
hydrogen, which was done on di
fferent apparatus. When asked why,
he said it was
because he couldn't get time on the program (because
there's so little time and it's such expensiv
e apparatus) to do the
experiment with light hydr
ogen on this apparatus because there
wouldn't be
any new result. And so the men in charge of programs
at NAL are so anxious for new results, in orde
r to get more money
to keep the thing going for p
ublic relations purposes, they are
ssibly--the value of the experiments themselves,
which is the whole purpose of the thing. It is often hard for the
experimenters there to complete t
heir work as their scientific
integrity demands.

All experiments in psychology are not of this
type, however. For
example, there have been many
experiments running rats through all
kinds of maz
es, and so on--with little clear result. But in 1937
a man named Young did a very interesting one.
He had a long
corridor with doors all along one s
ide where the rats came in, and
doors along the o
ther side where the food was. He wanted to see if
he could train the rats to go in at the third doo
r down from
wherever he started them off. No. The
rats went immediately to the
door where the food
had been the time before.

The question was, h
ow did the rats know, because the corridor was
beautifully built and so uniform, that this was the same door
as before? Obviously there was somet
hing about the door that was
different from the o
ther doors. So he painted the doors very
y, arranging the textures on the faces of the doors exactly
the same. Still the rats could tell. Th
en he thought maybe the rats
were smelling the fo
od, so he used chemicals to change the smell
r each run. Still the rats could tell. Then he realized the
rats might be able to tell by seeing th
e lights and the arrangement
in the laboratory li
ke any commonsense person. So he covered the
idor, and still the rats could tell.

He finall
y found that they could tell by the way the floor sounded
when they ran over it. And he could only
fix that by putting his
corridor in sand. So he c
overed one after another of all possible
clues an
d finally was able to fool the rats so that they had to
learn to go in the third door. If he relaxe
d any of his conditions,
the rats could tell.

Now, from a scientific standpoint, that is an A-n
experiment. That is the experiment that
makes rat-running
experiments sensible, because
it uncovers the clues that the rat
is really usin
g--not what you think it's using. And that is the
experiment that tells exactly what conditions you
have to use in
order to be careful and control e
verything in an experiment with

I looked into the subsequent history of this research. The next
experiment, and the one after that,
never referred to Mr. Young.
They never used any
of his criteria of putting the corridor on
or being very careful. They just went right on running rats
in the same old way, and paid no atten
tion to the great discoveries
of Mr. Young, and h
is papers are not referred to, because he didn't
discover anything about the rats. In fact, he discovered all the
things you have to do to discover
something about rats. But not
paying attention to
experiments like that is a characteristic of
go cult science.

Another example is the ESP ex
periments of Mr. Rhine, and other
people. As vari
ous people have made criticisms--and they themselves
have made criticisms of their own experiments-
-they improve the
techniques so that the effects
are smaller, and smaller, and
smaller until they
gradually disappear. All the parapsychologists
e looking for some experiment that can be repeated--that you can
do again and get the same effect--
statistically, even. They run a
million rats no,
it's people this time they do a lot of things and
get a certain statistical effect. Next time they
try it they don't
get it any more. And now you fi
nd a man saying that it is an
irrelevant demand t
o expect a repeatable experiment. This is

This man also speaks about a new institution
, in a talk in which
he was resigning as Director
of the Institute of Parapsychology.
And, in tell
ing people what to do next, he says that one of the
things they have to do is be sure they only tra
in students who have
shown their ability to get P
SI results to an acceptable extent--
not to waste
their time on those ambitious and interested students
who get only chance results. It is very dang
erous to have such a
policy in teaching--to teach
students only how to get certain
results, rather
than how to do an experiment with scientific

So I have just one wish for you--the g
ood luck to be somewhere
where you are free to ma
intain the kind of integrity I have
described, an
d where you do not feel forced by a need to maintain
your position in the organization, or financia
l support, or so on,
to lose your integrity. May
you have that freedom.