178 II. BIOLOGICAL  FOuNDATIONS
estimates, was based on 31 studies of dogs, 
and found a mean stability correlation of 
.43 for traits classified as belonging to one 
of six personality dimensions, namely activ -
ity, sociability, aggression, submissiveness, 
responsiveness to training, and fearfulness/
reactivity (Fratkin, Sinn, Patall, & Gosling, 
2013).
Animal personality studies based on be -
havioral observations or ratings often assess 
interjudge agreement reliability among the 
observers or raters. Reviews of the literature 
on multiple taxa (Freeman & Gosling, 2010; 
Gartner, 2014; Gartner & Weiss, 2013; 
Gosling, 2001; Jones & Gosling, 2005) all 
find interrater or interobserver reliability es -
timates comparable to those for established 
measures of human personality, such as the 
Revised NEO Personality Inventory (Costa 
& McCrae, 1992).
Studies that examine a broad range of 
traits have also found that, for a given spe -
cies, data reduction techniques tend to yield 
the same personality dimensions, regardless 
of the method used to collect the personal -
ity data (i.e., rating instruments or behav -
ioral observations). For example, studies of 
chimpanzees show that different rating in -
struments (Dutton, 2008; Dutton, Clark, & 
Dickins, 1997; Freeman et al., 2013; King & 
Figueredo, 1997) and behavioral measures 
(Koski, 2011b; Massen, Antonides, Arnold, 
Bionda, & Koski, 2013; van Hooff, 1970) 
identify the same dimensions or subsets of 
these dimensions. Similar results have been 
found in rating-  based studies of brown ca -
puchin monkeys that rely on different ques -
tionnaires developed on the basis of different 
principles (Morton, Lee, Buchanan-  Smith, 
et al., 2013; Uher, Addessi, & Visalberghi, 
2013). Rating-  based studies (Stevenson- 
Hinde & Zunz, 1978; Weiss, Adams, Wid -
dig, & Gerald, 2011) and observation-  based 
studies (Brent et al., 2014) of rhesus ma -
caques also yield similar sets of dimensions 
(see Weiss, 2017, for other examples). In 
short, for a given species, all the different 
types of personality instruments appear to 
measure the same set of constructs.
Validity
Attempts to establish the validity of rat -
ings of personality have met with success in nonhuman primates (Freeman & Gosling, 
2010), felids, the taxonomic group that in -
cludes cats (Gartner & Weiss, 2013), dogs 
and other household pets (Gartner, 2014; 
Jones & Gosling, 2005), and other species 
(Gosling, 2001). Much of the evidence for 
validity has been based on studies examining 
relationships between individual behaviors 
and ratings of single personality items or per -
sonality dimensions. However, recent stud -
ies have found associations between animal 
personality measures, based on either ratings 
or behaviors, and what would be referred to 
as “consequential outcomes” (Ozer & Benet-
Martínez, 2006) or “life outcomes” (Roberts, 
Kuncel, Shiner, Caspi, & Goldberg, 2007) 
in studies of humans. In Barbary macaques 
and barnacle geese, for example, personality 
traits are related to achieving high rank (e.g., 
Konečná, Weiss, Lhota, & Wallner, 2012; 
Kurvers et al., 2009). Moreover, personality 
traits are related to whether dogs can be suc -
cessfully trained to for certain “jobs,” such 
as being a detector dog (e.g., Harvey et al., 
2016; Maejima et al., 2007; Sinn, Gosling, 
& Hilliard, 2010). There are even links be -
tween primate personality and cognitive per -
formance measures analogous to “scholastic 
aptitude” (e.g., Altschul, Wallace, Sonnwe -
ber, Tomonaga, & Weiss, 2017; Altschul, 
Weiss, & Terrace, 2016; Carter, Marshall, 
Heinsohn, & Cowlishaw, 2014; Hopper et 
al., 2014; Morton, Lee, & Buchanan-  Smith, 
2013). For example, chimpanzees that were 
rated as higher in conscientiousness and 
openness 3 years earlier performed better 
on a touchscreen learning task, and higher 
openness predicted engaging in the learning 
task even when no reinforcers were delivered 
(Altschul et al., 2017).
In addition to the aforementioned at -
tempts to validate personality ratings, some 
researchers have used validity studies to 
challenge assumptions about measures of 
personality, such as behavioral tests or be -
havioral observations. For example, Cart -
er, Marshall, Heinsohn, and Cowlishaw 
(2012b) examined two purported behavioral 
measures of boldness (a novel object test and 
responses to a stuffed snake) in wild chacma 
baboons. They found that these measures 
were related to each other only weakly and 
probably defined separate constructs. As a 
consequence of these and related findings, 