Three Important Postwar Influences 77Darwinian principles that led to sociobiology, behavioral
ecology, and evolutionary psychology. Finally, the so-called
cognitive revolution had important effects on the field.
European Ethology
Three major influences have affected and reshaped compara-
tive psychology since World War II. The first was the full-
blown arrival of European ethology. Ethology is as difficult
to define as comparative psychology. It is a school of animal
behavior studies that was developed in Europe by Konrad
Lorenz, Niko Tinbergen, and their associates (Thorpe, 1979).
According to a common, though greatly exaggerated, way of
differentiating ethology from comparative psychology, the
former developed in European zoology with birds, fish, and
insects as subjects in observational studies and field experi-
ments designed to understand instinct and evolution. Com-
parative psychology is said to have developed within North
American comparative psychology with mammals, espe-
cially laboratory rats, as subjects in laboratory research
emphasizing experimental control and statistical analysis de-
signed to understand learning and development. Although
these differences in emphasis are instructive, the extent to
which they are exaggerations of comparative psychology
should be apparent to the reader. On the other side, Lorenz
himself conducted little field research.
Although European ethologists and American compara-
tive psychologists had numerous interactions prior to World
War II, it was only after the war that contact became exten-
sive. The two disciplines that had each developed as “the ob-
jective study of behavior” along different lines came into
direct conflict. Ethologists criticized psychologists for em-
phasizing laboratory research that may produce results irrele-
vant to the natural habitat; psychologists bemoaned the lack
of experimental control in fieldwork of the ethologists.
The most critical issues, however, centered about behav-
ioral development and the nature of instinctive behavior. The
battle over instinct had gone on in the United States for most
of the century, and during the 1950s, few psychologists ac-
cepted the concept; most emphasized the complex interaction
of genes and environment in epigenesis. Based on their field
observations, ethologists, by contrast, were quite comfortable
with discussions of instinctive behavior (e.g., Lorenz, 1950).
Lehrman (1953) wrote a scathing rebuttal to Lorenz’s ap-
proach, with particular criticism directed at the instinct con-
cept. On the one hand, the critique shocked ethologists and
polarized the fields; on the other hand, however, it placed the
issues out in the open where they could be debated and re-
solved. At a series of conferences, many of the differences
were softened and mutual understanding increased. One
anecdote is revealing. Lehrman was discussing the issues in a
rather stiff and formal disagreement with two ethologists,
Gerard Baerends and Jan van Iersel, in a hotel room in
Montreal. At one point, van Iersel’s attention was distracted
by a birdsong coming from the garden. Lehrman, a lifelong
bird-watcher, replied that it was a hermit thrush. Van Iersel
wanted to observe it, so the three went off on a birding expe-
dition. When they returned to the debate, their shared feeling
for animals lessened the hostility and fostered give-and-take
discussion (Beer, 1975).
Although some psychologists, such as Schneirla, saw little
value in ethology, others, like Lehrman and Beach, saw
much. Beach and Carpenter facilitated interaction by agree-
ing to serve on the founding editorial board of the ethological
journalBehaviour. Many students were attracted to the natu-
ralism of the ethological analyses and traveled to Europe to
work in ethological laboratories (Dewsbury, 1995). The two
fields changed in each other’s directions. Tinbergen moved
from the Netherlands to Oxford University and developed a
program with English-speaking ethologists. In general, they
moved more toward the American position than did the
German-speaking ethologists. The result of this activity was
a more unified approach to animal behavior studies, with
more psychologists even more concerned with naturally oc-
curring behavior and principles that would be valid in nature
and more ethologists concerned with control and experimen-
tal procedures. More and more psychologists participated in
the biannual International Ethological Conferences, and more
Europeans came to the United States for either short or ex-
tended periods of time. In the process, both fields benefited.Sociobiology, Behavioral Ecology,
and Evolutionary PsychologyThe second major postwar influence came from the field that
has become known as sociobiology. Many scientists had been
studying behavior from an evolutionary perspective for many
years. However, some of the implications of Darwinian theory
had not been fully thought through; this led to some question-
able interpretations. During the 1960s and early 1970s, theo-
rists such as William D. Hamilton, John Maynard Smith, and
Robert Trivers reinterpreted Darwinian principles. Although a
number of principles were reevaluated, two were critical. One
principle concerns the level at which natural selection acts.
Much had been written about how behavior evolves for the
good of the species or group. Thus, for example, reproduction
had been thought to have evolved for the perpetuation of
the species. On reinterpretation, it was concluded that
natural selection works primarily at the level of the individual
or gene, not the group or species. This had many important