Russell Hurlbert and David Likely mention a possibly apocryphal set of stories
(one involving Newton, the other involving Aristotle), the moral of which is that
an empirical attitude is necessary in science. For no good reason other than I got
here earlier than usual and I find the topic interesting, I can relate to you a
fascinating (and definitely true) story making a similar point from the field of
human genetics. According to Daniel Kevles (1985; _In the name of eugenics:
Genetics and the uses of human heredity_, New York: Knopf), from the 1920s until
1955, the number of human chromosomes was believed to be 48. In 1955, two plant
cytologists by the names of Joe-Hin Tjio and Albert Levan established beyond a
doubt that the number of human chromosomes was 46, two less than the number that
had been reported in paper after paper since the 1920s.
The story begins in the 1890s, with the first counts of human chromosomes in
corpses:
"The very early counts had yielded numbers that varied around twenty-four, which
was consistent with those obtained for other mammals. The trouble then was that
cytologists made their counts with tissue taken from corpses, often those of
executed criminals; upon the death of mammalian cells, the chromosomes tend to
clump together rapidly, thus deceiving even the microscope-aided eye into falsely
low counts." (p. 238)
The problem of the clumping of chromosomes occurred, however, even in the best
preparations using fresh tissue from surgical operations. Nevertheless, if one
took great care in preparing one's slides, it seemed that there was enough
separation of chromosomes to get fairly accurate counts. In 1912, one cytologist
counted 47 chromosomes in males and 48 in females. During the early 1920s,
Theophilus Painter obtained testes from institutionalized mentasl patients (who
had been castrated because of "excessive self-abuse coupled with certain phases of
insanity"). He found what he thought were unambiguous counts of 48 chromosomes,
and thereby established that the number of chromosomes was equal in males and
females. Not until Tjio and Levan used better techniques for preparing slides in
1955, was the number corrected to 46 chromosomes for both males and females.
Why was the incorrect number obtained by so many cytologists for over a 30-year
period? Why did no one ever disagree with this count? There seems little doubt
that other researchers sometimes found the correct number (see below).
Nevertheless, they all reported that they had found 48 chromsomes. Why? Kevles
offered the following explanation:
"The human cytogeneticist often had to wait...outside operating rooms or...at the
foot of the gallows. Once obtained and fixed, the specimens were sliced into thin
sections with a fine blade--the blade cutting through the nucleus of a given cell
as a knife might cut through an egg in the middle of a meat loaf.... [S]uccessive
sections of cell...would include serial slices of the complete nucleus.... The
cytologist added the number found in each section to reach the total in the cell.
But because of the imprecision in where the blade happened to cut, fragments of a
chromosome located--and already counted--in one section might turn up as
candidates for counting in the next.... They [the chromosomes] appeared to
cytologists of Painter's era as something like the noodles in a soup--some lying
beneath others and difficult to count accurately." (pp. 239-40)
Thus, cytologists who looked at such preparations could not be certain if any two
black lines on two successive slides were pieces of one chromosome or two separate
ones:
"Every enumeration of human chromosomes required judgement, AND JUDGEMENT LEFT
ROOM FOR CONFORMATION TO ORTHODOXY. Human chromosomal counts sometimes suggested a
figure different from forty-eight, but most cytologists, EXPECTING TO DETECT
PAINTER'S NUMBER, VIRTUALLY ALWAYS DID SO." (p. 240; emphasis added)
For example, the cytologist Tao-Chiuh Hsu, who was instrumental in developing part
of the technique that eventually allowed the correct count of human chromosomes,
was led by his preconceptions to report 48 chromosomes, even when he had counted
46. In 1952, in slides that he had prepared using an improved technique that led
to more dispersed chromosomes, he often was able to see relatively clearly that
there might be only 46 chromsomes:
"In many cells, he recalled with some irony, 'I had difficulty getting the count
to equal forty-eight.' Nevertheless, his vision filtered through the prevailing
preconception, Hsu managed to count Painter's figure. He later confessed to
feeling like a football player who returns an interception forty yards only to
find himself 'fumbling the ball at the three-yard line.'" (p. 241)
Three years later, when Tjio and Levan used further improvements to prepare their
slides, they found an unambiguous count of 46 chromosomes. Nevertheless, they
still felt some "residual anxiety about challenging Painter's much-confirmed
number" (p. 241).
Ever since I first read this account 14 years ago, I have been fascinated by this
story. For me, it takes on added significance when one realizes that such a
mistake (thought to be based on the most careful empiricism) was transmitted down
the scientific lineage, thereby influencing the observations of later scientists.
Just think how much more of a problem this might be for a discipline such as
psychology where the subject matter often is not anything physical at all. Most
psychological research involves the study of phenomena that cannot be directly
observed--research that is much more complex than the simple counting of physical
objects. It makes me realize how difficult our science is, and how easily mistakes
might get propagated (Freudian psychoanalysis is only one extreme example of
this).
Well, I guess I should do something useful,
Jeff
--
Jeffry P. Ricker, Ph.D. Office Phone: (480) 423-6213
9000 E. Chaparral Rd. FAX Number: (480) 423-6298
Psychology Department [EMAIL PROTECTED]
Scottsdale Community College
Scottsdale, AZ 85256-2626
"The truth is rare and never simple."
Oscar Wilde
"No one can accept the fundamental hypotheses of scientific psychology
and be in the least mystical."
Knight Dunlap
