176 
Whether looking at people or animals, two 
observations have been made by psycholo -
gists, biologists, and lay observers. First, 
individuals differ consistently in how they 
behave and react toward, and think about, 
the world around them. Second, not all these 
differences are independent of one another: 
Individuals who are high (or low) on some 
traits tend to be high (or low) on other traits. 
In more formal language, individuals can be 
characterized by stable individual differenc -
es in personality traits, and these traits have 
a structure to them.
Scientific studies of human personality 
can be traced back at least to the work of 
Sir Francis Galton (1884) who lived from 
1822 to 1911. For a long time, this work 
was predominantly descriptive (see also 
John, Chapter 2, this volume). Researchers, 
for example, would identify and categorize 
personality traits, whether by studying the 
natural language of populations (Allport 
& Odbert, 1936) or by analyzing data de -
rived from questionnaires, naturally occur -
ring behaviors, and behavioral tests (Cattell, 
1946). The descriptive flavor of this early 
research was, and continues to be, criticized 
by some authors (e.g., Block, 1995; Eysenck, 
1992; Uher, 2013). However, gathering de -tailed, descriptive data is a crucial first step 
in any scientific discipline (Chamberlin, 
1890/1965). In fact, that description should 
come before theory has been recognized for 
a long time in the field of animal behavior 
(Tinbergen, 1959, 1963), and this recogni -
tion likely contributed to the emergence of 
animal personality research in that field.
This chapter examines how the study of 
personality in nonhuman animals contrib -
utes to our understanding of personality in 
general and of human personality in par -
ticular. For one, animal research has helped 
elucidate the evolutionary bases of person -
ality variation and structure by the method 
of exclusion (Platt, 1964). In other words, 
this research has shown that some proposed 
evolutionary explanations for personality 
are not likely to be true. In addition, per -
sonality research on animals contributes to 
our understanding of the neuroanatomical 
bases of personality variation, informs the 
debate about the origins and magnitude of 
age differences in personality, and addresses 
why the personalities of some people predis -
pose them to be happier than others. Read -
ers of this chapter who are familiar with 
Gosling’s (2001) review of the literature will 
thus see that research in animal personality CHAPTER 7
Personality in  Animals
What Can We Learn from  
a Species‑Comparative Approach?
Alexander  Weiss