COGNITIVE SCIENCE 14, 281-312 (1990)
Laboratory Replication
of Scientific Discovery Processes
YULIN QIN AND HERBERT A. SIMON
Carnegie-Mellon University
Fourteen subjects were tape-recorded while they undertook to find a law to sum-
marize numerical doto they were given. The source of the data was not identified,
nor were the variables lobeled semantically. Unknown to the subjects. the data
were measurements of the distances of the planets from the sun and the periods
of their revolutions obout it-equivalent to the doto used by Johonnes Kepler to
discover his third low of planetary motion.
Four of the 14 subjects discovered the some low as Kepler did (the period
varies OS the 3/2 power of the distance), and a fifth come very close to the
answer. The subiects’ protocols provide a detatled picture of the problem-solving
searches they engoged in, which were mainly, but not exclusively, in the space of
possible functions for fitting the data. and provide explanations OS to why some
succeeded and the others foiled.
The scorch heuristics used by the subjects ore similar to those embodied in
the BACON program, a computer simulation of certain scientific discovery pro-
cesses. The experiment demonstrates the feasibility of examining some of the
processes of scientific discovery by recreating, in the laboratory, discovery situa-
tions of substontiol historical relevance. It demonstrates also. that under condi-
tions rather similar to those of the originol discoverer, a low can be rediscovered
by persons of ordinory intelligence (i.e., the intelligence needed for academic
success in a good university). The data for the successful subjects reveal no
“creative” processes in this kind of o discovery situation different from those that
are regulorly observed in all kinds of problem-solving settings.
In 1618, Johannes Kepler discovered his third law of planetary motion: The
cube of a planet’s distance from the sun is proportional to the square of its
period of revolution, or:
This research was supported by the Personnel and Training Programs, Psychological Sci-
ences Division, Office of Naval Research, under Contract No. NC0014-86-K-0768; and by the
Defense Advanced Research Projects Agency, Department of Defense, ARPA Order 3597,
monitored by the Air Force Avionics Laboratory under contract P33615-81-K-1539. Repro-
duction in whole or in part is permitted for any purpose of the United States Government.
Approved for public release; distribution unlimited.
Correspondence and requests for reprints should be sent to Herbert A. Simon, Department
of Psychology, Carnegie-Mellon University, Pittsburgh, PA 15213.
281

282 QIN AND SIMON
d/PZ= c,
where D is the distance, P the period, and C a constant. This discovery, along
with Kepler’s laws of elliptical orbits and equal. areas, paved the way for
Newton’s discovery of the law of universal gravitation, from which Kepler’s
laws can be deduced logically.
The discovery of the third law provides a setting for the study of some
of the processes that people (scientists) use to find regularities in data,
especially in the frequent circumstances where there exist no bodies of rele-
vant theory to guide the search. In this instance, as in many others in the
history of natural science, the discovery requires an induction directly from
the data without help from preexisting theory. Data-driven discovery of this
kind has been simulated by the BACON program (Langley, Simon, Brad-
shaw, & Zytkow, 1987), which, using a few simple heuristics, rediscovered
Kepler’s third law, as well as Ohm’s law of electrical currents, Black’s law
of temperature equilibrium, and a substantial number of other important
laws of eighteenth and nineteenth century chemistry and physics. Langley et
al. (1987) also discuss the significance of data-driven discovery in the overall
progress of science.
The purpose of the experiments described in this article was to compare
human data-driven discovery processes with the processes embodied in
BACON, and thereby to determine their similarities and differences. Do
humans use the same heuristics as BACON when they are confronted with
the Kepler data? Unfortunately, it is too late to take a protocol from
Kepler, who left behind only a minimal record of how he found the thiid
law. As possibly inadequate substitutes for Kepler, college students were
recruited for two closely similar experiments. The data obtained from these
experiments give evidence of how human subjects respond to their task and
how their methods compare with BACON’s, and perhaps cast some light on
the history of scientific discovery in the case of Kepler’s third law. First, the
experiments and their results will be described, followed by a discussion of
their significance for the psychology of discovery viewed as problem solv-
ing, and, finally, by questions about what light they may cast on Kepler’s
discovery.
EXPERIMENT 1
Method and Material
The data used in this experiment were the average distances from the sun, and
the periods of revolution about the Sun of Mercury, Venus, Earth, Mars and
Jupiter, obtained from the 1986 World Almanac. Kepler in the seventeenth
century, used only slightly less precise data (See Harmonies of the World,
1619/1952, Chapters, 3,4.) The data given to the subjects (Table 1) were not