Conclusion: Persistent Issues 79cognition, and language (Roitblat, 1987; Shettleworth, 1998;
Vauclair, 1996). The most publicized research in this field
has been that of language learning. Although there had been
earlier attempts to teach language to apes, such as that of
Cathy and Keith Hayes at the Yerkes Laboratories (Hayes,
1951), three major approaches developed during the 1960s
and 1970s. Gardner and Gardner (1969) taught American
sign language to chimpanzee Washoe; Rumbaugh (e.g.,
Rumbaugh & Gill, 1976) studied acquisition of a computer-
based language in chimpanzee Lana; and Premack (1971)
used a system of sentence formation using pieces of plastic
with chimpanzee Sarah. This groundbreaking research was
both heavily criticized and staunchly defended. This pro-
duced a fallow period, due largely to an absence of funding,
during which little language research was conducted. This
period was followed by a reformulation and rebirth of studies
of animal language, the most remarkable of which were of
bonobo Kanzi, who learned a symbol-based language with-
out overt training and became efficient in interpreting human
speech (e.g., Savage-Rumbaugh et al., 1993). Other studies
of language acquisition were conducted with an African grey
parrot (Pepperberg, 1999), dolphins (Herman, 1987), and sea
lions (Schusterman & Krieger, 1984).
Many of the studies in animal cognition were derived
from, and closely related to, traditional research in animal
learning. Other scientists made an effort to more completely
revolutionize the field of animal cognition using language
suggestive of conscious processes in animals. Leading the
latter effort was American ethologist Donald R. Griffin (e.g.,
Griffin, 1976b); the field became known as cognitive ethol-
ogy. Advocates of this approach contended that, with ad-
vances in methodology, there are now available methods that
can provide windows to the minds of animals. According to
Griffin (1976a), “the hypothesis that some animals are indeed
aware of what they do, and of internal images that affect their
behavior, simplifies our view of the universe by removing the
need to maintain an unparsimonious assumption that our
species is qualitatively unique in this important attribute”
(p. 534). Critics disagreed, contending that no methods were
yet available that enable scientists to observe the internal
processes of animal minds.
Among the focal areas of research in cognitive ethology
have been studies of self-recognition in mirrors (e.g., Gallup,
1985). According to Gallup, humans, chimpanzees, orang-
utans, and some gorillas are the only species to show evi-
dence of self-recognition when presented with mirrors. The
key evidence comes from “dot tests,” in which a dot is painted
onto the forehead of an anesthetized animal to see if the ani-
mal selectively touches the dot when awakened and presented
with a mirror. Gallup believes that such behavior suggests
awareness, self-awareness, and mind in chimpanzees. Critics
disagree (Heyes, 1994). In some ways, the field had returned
to questions addressed a century ago. Psychologists disagree
as to whether the results achieved during that century now
permit a return to these questions in a more sophisticated
manner or whether it is regressing to an earlier state.CONCLUSION: PERSISTENT ISSUESLooking back over a little more than a century of compara-
tive psychology, a number of characteristics are apparent.
The conceptual foundations of comparative psychology have
changed greatly. Some of these changes have been generated
from within the field; many more have been stimulated from
related fields. Comparative psychologists have excelled in
doing research and greatly expanded the body of data avail-
able. It is this mass of information, sometimes well organized
and sometimes rather scattered, that has enabled a century of
change. Comparative psychologists have been empiricists
working to expand the observational and experimental foun-
dation of the field; there are few postmodern comparative
psychologists. In spite of the changes that have occurred,
however, throughout the century there have been some per-
sistent issues that have characterized the field.
Surely the first issue lies in the very definition of compar-
ative psychology. Although comparative psychologists have
written much about this problem, few have been truly both-
ered by it. Even lacking a clear definition, most comparative
psychologists have ignored the fuzzy boundaries of the field
and concentrated on the business of studying animals and
building general principles of behavior.
Underlying the research effort have been issues of method-
ology. The field has been characterized by eclecticism, as
most researchers have used whatever methods have appeared
appropriate for the problem under study. Although some com-
parative psychologists, such as Carpenter, Schneirla, Yerkes,
Mason, and others, have conducted field research, most have
preferred the controlled conditions of the laboratory. Not all
comparative psychologists make overt comparisons among
species; the goal is not one of comparison for the sake of com-
parison but rather the development of principles of generality.
Although some, such as Kline, Schneirla, and James V.
McConnell, have studied invertebrates, most have concen-
trated on vertebrates, especially mammals. Some, such as
Beach, Lehrman, and Carpenter, have concentrated on natu-
rally occurring behavioral patterns; others have turned their
attention to the study of learning and motivation in a compar-
ative context. Although experimentation is the preferred
method, many observational and correlational studies have
been important. The anecdotes that characterized early re-
search disappeared as laboratory methodology became more