78 Comparative Psychology
implications and permitted reinterpretation of many phenom-
ena. If a nest of eggs is left unguarded in a colony of gulls, for
example, other members of the colony will eat the eggs. This
makes little sense if all were there to perpetuate the species but
is easy to understand if competition was at the level of the in-
dividual, with each selected to get its genes into the next gen-
eration. It had been believed that, at high densities, some
species temporarily curtail reproduction in order not to over-
exploit the available environmental resources. This became
reinterpreted as a temporary “strategy” that could benefit the
lifetime reproductive success of an individual by preserving
energy during hard times. The extreme form of this approach
was Richard Dawkins’s (1976) selfish gene theory.
The second new principle concerned inclusive fitness. The
termfitnessrefers to the relative contribution of different in-
dividuals to future gene pools. It was noted that an individual
shares more genes with close relatives than with those to
which one is unrelated. There are thus at least two ways in
which one’s genes can be transmitted to the next generation.
One is through reproduction (direct fitness); the other is
through facilitating the reproduction of close relatives (indi-
rect fitness or kin selection). Inclusive fitness is, essentially,
the sum of the two. Thus, what might appear to be altruistic
behavior, which might lower one’s fitness, might be adaptive
in the long run. One might lower one’s direct fitness but gain
even more indirect fitness in the process. The bottom line
became lifetime inclusive fitness.
These two principles, and some others associated with
them, led many students of animal behavior, both inside and
outside of psychology, to reorient their research programs.
Many students became interested in the study of the evolu-
tionary causes of behavior (ultimate causation) as opposed to
the immediate and developmental causes (proximate causa-
tion). There were many studies of the role of kinship in be-
havior. A large number of species were found to modulate
their behavior depending on the degree of kinship shared
with others with which they interacted (e.g., Holmes &
Sherman, 1982; R. H. Porter, 1988). Sexual selection, a topic
emphasized by Darwin in 1871, became a major focus of
research, with psychologists emphasizing studies of mate
choice (e.g., Beauchamp, Yamazaki, & Boyse, 1985) and
male–male competition for mates (e.g., LeBoeuf, 1974). Oth-
ers sharpened evolutionary interpretations of phenomena of
research on learning (e.g., Hollis, 1990; Kamil & Clements,
1990; Timberlake, 1990). Evolutionary perspectives had
been a part of comparative psychology since its founding;
now studies became more refined and were addressed more
specifically to evolutionary principles.
This orientation had been somewhat diffuse until E. O.
Wilson (1975) organized and named the field in his Sociobi-
ology: The New Synthesis. Although Wilson predicted the
demise of comparative psychology, the field was, in fact,
strengthened by the new perspective. The first 26 chapters of
Wilson’s book provided a synthesis of much work related to
the ultimate causation of animal behavior. In the final chap-
ter, however, Wilson applied these principles to human be-
havior. This approach proved highly controversial. Although
some careful research on human behavior stemmed from this
approach (e.g., Daly & Wilson, 1978), other writings rested
on less solid ground. A split developed between the contro-
versial studies of human behavior and those less controver-
sial studies of animals. The term behavioral ecologywas
coined, in part, so that students of animal behavior could dis-
tance themselves from some of the more speculative studies
of humans.
More recently, sociobiology has been reborn asevolu-
tionary psychology. An emphasis in the older sociobiology
had been upon the ways in which existing patterns of
human behavior enhanced fitness. In the newer perspective,
the focus shifted to adaptiveness at the time that mecha-
nisms of behavior evolved in the ancestors of humans, and
it was recognized that many behavior patterns and tenden-
cies, such as our attraction to sweet foods, might not be as
adaptive under present conditions (e.g., Cosmides & Tooby,
1987).Comparative CognitionThe third major influence on comparative psychology since
World War II was from the “cognitive revolution.” According
to the received view, the hegemony of behaviorism precluded
cognitive approaches to behavior prior to the 1960s and a
major revolution occurred thereafter. In fact, however, re-
search with a cognitive orientation has long been a part of
comparative psychology (e.g., Dewsbury, 2000; Wasserman,
1993). Although a case can be made that there was no true
revolution (Leahey, 1992), it is clear that in recent years cog-
nitive perspectives have achieved a prominence in compara-
tive psychology that had not been apparent previously.
This increased emphasis on cognitive perspectives was a
part of the broad upsurge of interest in cognitive processes
throughout psychology and related disciplines. Develop-
ments in information processing, computers, and mathemati-
cal logic fostered a reconstruction of psychology as a science
of information as well as behavior. Some psychologists
moved to overcome what they perceived as the counterpro-
ductive constraints imposed by more behavioristic theories.
Interest was directed in the manner in which animals
represent their worlds and the consequences of such repre-
sentation for behavior.
Among the topics receiving renewed interest were atten-
tion, memory, timing, concept formation, counting, social