Ch. 5— The Use of Animals in Research • 101 
age, epilepsy, schizophrenia, depression, learn- 
ing disorders, smoking, anorexia nervosa, stomach 
ulcers, mental retardation, and a variety of other 
psychological disorders. 
Why Are Animals Used in 
Behavioral Research ? 
Control 
The use of animals under laboratory conditions 
enables the manipulation and control of a vari- 
ety of factors that in different settings would con- 
fuse, contaminate, and confound any attempt to 
interpret a behavioral outcome. Animal models 
also allow the control of genetic background, 
prior experience, temperature, humidity, diet, 
and previous social encounters. When these vari- 
ables are uncontrolled, observed behavioral re- 
sponses can be virtually impossible to interpret. 
Objectivity 
Two prerequisites to any research are objec- 
tivity and impartiality. When humans study hu- 
mans, as can be the case in behavioral research, 
unique problems may arise. Not only can it be dif- 
ficult for the investigator to remain objective in 
interpreting behavioral phenomena, but a vari- 
ety of other complications can arise from the so- 
cial relationship among those conducting the re- 
search and those participating as subjects (50). 
The use of nonhuman species partially amelio- 
rates this problem. 
Developmental Effects 
Among many species behavior changes as a 
function of age. The problem this poses for hu- 
man research is one of time. Human development 
continues for many decades. To chart behavioral 
changes within the same persons would take 
many years, involving exhaustive followup studies 
and the ever-present danger of losing research 
subjects, for example, because of death or relo- 
cation. The alternative to such longitudinal work 
is to conduct cross-sectional studies, where simul- 
taneous samples are drawn from different age 
groups. A problem in this case is that sociologi- 
cal and cultural changes over time (e.g., 50 years 
ago, an eighth-grade education was the norm) 
confound apparent differences between people 
of different ages. Because a range of lifespans is 
available among laboratory species, the use of ani- 
mal models can minimize or circumvent al- 
together some problems associated with the study 
of behavior over time. 
Genetic Effects 
There is growing evidence of a variety of ge- 
netic effects on behavior (23). With animal models, 
selective breeding studies can establish, pinpoint, 
and quantify genetic effects on behavior. The op- 
portunity for human research in this area, apart 
from studies of identical twins, is limited. 
Methodology 
The fact that animals cannot talk seems at first 
to constitute a serious disadvantage to conduct- 
ing behavioral research with animals. Yet, the 
stark limits of trans -species communication help 
to keep human investigators unbiased in their 
work. The use of animal models forces the be- 
havioral scientist to develop objective, operational 
definitions and research techniques that may later 
be applied to humans. 
Lower Complexity 
Behavior, notably human behavior, can be ex- 
tremely complex. The use of animals that appear 
to be structurally and functionally less complex 
presents a way to identify some of the basic ele- 
ments and principles of behavior that might other- 
wise remain inextricably embedded in a mosaic 
of other factors. 
Species-Specific Behaviors 
Certain behavioral phenomena fall outside the 
realm of human sensory or motor abilities. For 
example, flight, echolocation, infrared detection, 
and homing require the use of nonhuman spe- 
cies as subjects for research purposes. 
Heuristic Value 
Research on the behavior of animals has been 
an important source of hypotheses about human 
behavior and an impetus to research on humans 
(35). Much of what is now known about the prin- 
