68 Comparative Psychology
This was followed by a postwar period of decline, as younger
comparative psychologists were unable to sustain careers,
and then by a resurgence of activity between the world wars.
The field has remained active since World War II and
has been strongly influenced by developments in European
ethology, sociobiology, and cognitive science.
EARLY HISTORY
Humans have a long history of interest in animal behavior.
Perhaps the first evidence of this is from the cave paintings
depicting animals in southern Europe dating from the Upper
Paleolithic period, 35,000 to 10,000 years before the present.
Domestication of animals began about 11,500 years ago in
the Middle East and Asia (Singer, 1981). Among the ancient
Greeks, Herodotus (c. 425 B.C.) described habits and behav-
ior of animals and made observations on animal physiology.
Interest in animals was brought to a new level by Aristotle
(384–322B.C.). He relied on observation and inductive rea-
soning, not just speculation, to develop a natural history of
many species. Aristotle believed in the continuity of species,
though he believed species to be fixed rather than evolving.
He also proposed the notion of a Scala naturae,a single di-
mension along which all species could be ordered. Although
this idea, transformed from dealing with the characteristics of
the animals’ souls to their level of intelligence, is still popu-
lar today, it is widely regarded as fallacious. Evolution is
branching, and species do not lie along a single continuum.
During the long period from the ancient Greeks to the
mid-nineteenth century, interest in animal behavior was
strong in three areas. Such individuals as Frederick II of
Hohenstaufen (1194–1250), John Ray (1627–1705), and
Charles George Leroy (1723–1757), studied animal behavior
in nature and developed the area of natural history. A second
area was applied animal behavior,where domestication and
selective breeding of livestock, dogs, and other species con-
tinued and was perfected. Falconers developed remarkable
skills in the control of behavior (Mountjoy, 1980).
Finally, the relation between human and nonhuman
animals became an area of interest to philosophers. The
seventeenth-century French philosopher René Descartes is
credited with popularizing the view that there is an absolute
gulf between humans and all other species. According to
Descartes, humans are the only ones to possess the immate-
rial rational soul that enables abstract reasoning and self-
awareness; animals are automata that can carry on simple
mental functions but cannot think or have language. Darwin’s
work would discredit this dichotomy. An interesting di-
chotomy developed between the British and continental
philosophers regarding the developmental origins of ideas.
British philosophers such as John Locke and David Hume be-
lieved that all knowledge originated in experience. For Locke,
the mind was atabula rasa,or blank slate. Continental philoso-
phers, such as Immanuel Kant, proposed the existence of an ac-
tive mind with a priori properties, such as categories, that acted
on experience to produce knowledge. This geographic differ-
ence can be seen in contrasting the British and continental ap-
proaches to the field of ethology in the twentieth century.FORERUNNERS OF COMPARATIVE
PSYCHOLOGYThe intellectual grounding for a comparative psychology was
provided in the nineteenth century with the development of
the theory of evolution. The notion that evolution had oc-
curred did not originate with Charles Darwin but rather de-
veloped with the work of such individuals as Erasmus
Darwin (his grandfather), Jean-Baptiste Pierre Antoinne de
Monet de Lamarck, and Robert Chambers. Darwin provided
a viable mechanism, the theory of natural selection, and es-
tablished that no mystical forces affected the direction of
evolutionary change. Change is the result of differential re-
production under prevailing circumstances. What was critical
for comparative psychology was the solidification of the idea
that human and nonhuman animal behavior is continuous and
thus both can be studied and compared with similar methods.
This need not imply that there are no important differences
between humans and nonhuman animals (henceforth called
animals), but only that there are similarities and that any dif-
ferences will best be revealed through careful comparisons.
Although his Origin of Species(1859) and Descent of Man
(1871) are Darwin’s best-known works, The Expression of
the Emotions in Man and Animals(1872) was especially im-
portant for comparative psychology because it showed how a
comparative study of behavior might be conducted. Among
Darwin’s many contributions to comparative psychology, we
should remember that in the 1871 work Darwin laid out im-
portant principles of sexual selection, the manner in which
individual males and females find mates and achieve repro-
ductive success. Sexual selection has been an important topic
in the field of comparative psychology in recent years.
Darwin’s protégé was George John Romanes, an excellent
scientist, who worked with jellyfish, starfish, and sea urchins
(Romanes, 1885). He was also committed to demonstrating
Darwin’s principle of continuity in instinct and mind in hu-
mans and animals. In Animal Intelligence(1882), Romanes,
like most of his contemporaries, relied heavily on anecdotes,
reports of single instances of behavior provided by various