The Twentieth Century 327experimental work, which was published from 1895 onward
in his series of volumesPsychlogischen Arbeiten,still remains
untranslated (Kraepelin, 1915).
Kraepelin’s work was guided by the basic assumption that
all psychopathological behaviors arise from some defect in
nervous system function. The task was to measure nervous
system functions as carefully and quantitatively as possible.
The kind of defect discovered could help explain the clinical
phenomena that had led to the diagnosis. Measuring proce-
dures were limited to those that could be applied externally
(i.e., without invasion of tissue). The use of experimental
methods and quantitative measurement in medical research
generally was still in an early stage. It is noteworthy that
Kraepelin had no method for observing or measuring brain
functions in the living human being. Modern methods of
electroencephalography and brain imaging lay far in the fu-
ture. Postmortem examination of the brain provided opportu-
nity to measure structure, but not function.
Kraepelin and his colleagues regarded experimental psy-
chology and experimental physiology as a unitary domain of
study. The functions examined included motor movements,
reaction time to various kinds of stimulus, memory, word
associations, and mental work (simple calculations). Control
comparisons were made between patients and nonpatients.
The diagnostic categories of the patients involved included
paresis, dementia praecox (schizophrenia), neurasthenia, and
epilepsy. Although Kraepelin emphasized quantitative mea-
surement, no statistical tests available could assess the relia-
bility of the differences that he found, which limited him to
reporting absolute differences. In this respect, too, his situa-
tion was the same as that generally prevalent in medical
research at that time.
The investigation of psychophysical and physiological
factors in mental illness became a continuing theme in the
ensuing decades. Psychological laboratories were estab-
lished in the early twentieth century at McLean Hospital in
Massachusetts, the Worcester State Hospital, and the New
York State Psychiatric Institute. Some laboratories were situ-
ated in academic institutions, notably at Yale University,
where Edward Scripture conducted studies on reaction time
in various diagnostic groups. Hunt (1936) and Shakow
(1971) include useful reviews of the development of experi-
mental psychopathology during this period.
With increasing hegemony of psychoanalysis in American
academic psychiatry in the period immediately following
World War II, experimental research into psychopathology
experienced a decline. One triumphant analyst chronicled
this change with the assertion that “psychological apparatus
had found its way to the lumber rooms of psychiatric clinics,
covered with dust and rusting away without having left
behind any gap in the resources of the research worker and
the practitioner” (Maher & Maher, 1979).The Conditioned ReflexRussian physiologist Ivan Pavlov (1849–1936) was one of
the most influential scientists of his time. Although his work
was almost exclusively concerned with animals, he made sig-
nificant contributions to human psychopathology. In 1914, in
the course of conducting an experimental investigation of
discrimination in a dog, Pavlov made a finding of signifi-
cance to the understanding of neurosis. While investigating
the dog’s capacity to discriminate between different shapes,
the shapes were progressively altered until no discrimination
could be made. When the hitherto quiet dog was brought
back into the laboratory room, it struggled when harnessed in
its stand, whined, and bit at the apparatus. “In short,” wrote
Pavlov, “it presented all of the symptoms of a condition of
acute neurosis.” (Pavlov, 1927/1960, p. 291). Further re-
search was undertaken with dogs differing in temperament,
one type being extremely excitable, the other type extremely
inhibitable. The results led Pavlov to conclude that experi-
mental neurosis develops only in animals of extreme types,
and the symptoms of neurosis differ in the two types and
relate to the characteristics of the animals’ different nervous
organizations.
Coincidentally, a violent storm flooded Petrograd, and the
dogs had to swim from the kennels to the laboratory. After
this experience some of them displayed disturbed behavior
similar to the “experimental neuroses” obtained in the labo-
ratory. Pavlov concluded that “...a development of a
chronic pathological state of the hemispheres can occur
from... first a conflict between excitation and inhibition
which the cortex finds itself unable to resolve; second the ac-
tion of extremely powerful and unusual stimuli.” (Pavlov,
1957, p. 318). Pavlov linked the phenomena seen in labora-
tory studies of animals with those seen in human psy-
chopathology in a manner that was to influence experimental
psychopathology for several decades to come.
Much later, Howard Liddell at Cornell University investi-
gated the adaptive behavior of sheep and goats in which the
thyroid had been removed. Using a mild shock, Liddell was
interested in how long the animal would require to make a
conditioned anticipatory response. Both animals with and
without thyroid glands learned this quite readily. Because of
time pressure to complete his experiments, he increased
the number of trials at each testing session. This had the
unexpected effect of producing an experimental neurosis in
certain sheep. They showed excitement, alarm, struggled to
escape, showed rapid heart rate and breathing, micturation