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The genetic contribution to canine personality
P. Saetre
†,‡
, E. Strandberg
§
, P.-E. Sundgren
§
,
U. Pettersson
†
, E. Jazin
‡
and T. F. Bergstro¨m
†,{,
*
†
Department of Genetics and Pathology, Rudbeck Laboratory,
‡
Department of Evolutionary Biology, Uppsala University,
§
Department of Animal Breeding and Genetics, Swedish
University of Agricultural Sciences,
¶
The Linnaeus Centre for
Bioinformatics, Uppsala University, Uppsala, Sweden
*Corresponding author: T. F. Bergstro¨ m, Department of
Genetics and Pathology, Rudbeck Laboratory, S-751 85
Uppsala, Sweden. E-mail: tomas.bergstrom@genpat.uu.se
The domestic dog may be exceptionally well suited for
behavioral genetic studies owing to its population his-
tory and the striking behavior differences among breeds.
To explore to what extent and how behavioral traits are
transmitted between generations, heritabilities and
genetic correlations for behavioral traits were estimated
in a cohort containing over 10 000 behaviorally tested
German shepherd and Rottweiler dogs. In both breeds,
the pattern of co-inheritance was found to be similar for
the 16 examined behavioral traits. Furthermore, over
50% of the additive genetic variation of the behavioral
traits could be explained by one underlying principal
component, indicating a shared genetic component
behind most of the examined behavioral traits. Only
aggression appears to be inherited independently of
the other traits. The results support a genetic basis for
a broad personality trait previously named shyness–
boldness dimension, and heritability was estimated to
be 0.25 in the two breeds. Therefore, breeds of dogs
appear to constitute a valuable resource for behavioral
genetic research on the normal behavioral differences in
broad personality traits.
Keywords: Behavioral genetics, behavioral test, Canis famil-
iaris, dog, genetic correlations, heritability, personality trait
Received 16 March 2005, accepted for publication 28 April
2005
Personality refers to the behavioral characteristics of individ-
uals that describe and account for consistent patterns of
normal behavior that are stable across time and situations
(Plomin & Caspi 1999). There are several working models for
human personality traits, including the three-factor models
proposed by Eysenck and Eysenck (1985) and Tellegen
(1985) and the five-factor model proposed by Goldberg
(1990). Research focused on comparative animal personality
has revealed a number of trans-species personality traits
including fearfulness, exploration, sociability, aggressiveness
and activity level, suggesting that some personality traits
have been evolutionary conserved (Gosling 2001; Gosling &
John 1999). The complex personality phenotypes are
thought to be influenced by many environmental factors
and multiple genes (Bouchard 1994; Plomin et al. 1994).
Currently, only a handful of genes have been associated
with personality traits in humans, and their effect on the
variation of normal behavioral phenotypes is usually limited
(Benjamin et al. 1996; Caspi et al. 2002; Murphy et al. 2001).
However, animal models offer a promising approach to
detect the genetic components of complex behavioral traits
(Flint 2003).
An often-overlooked resource for behavioral genetics is
the domestic dog. This species is an exceptional organism
in that it has been bred specifically for different behaviors
(Ostrander et al. 2000). During the domestication of dogs,
there have been a variety of selective pressures (Clutton-
Brock 1999), and as a result, modern breeds of dogs display
striking behavioral differences such as emotionality, aggres-
siveness, activity and predatory behavior (Coppinger &
Schneider 1995; Coppinger et al. 1987; Hart & Miller 1985;
Murphree et al. 1977; Overall 2000; Scott & Fuller 1966;
Shekhar et al. 2001). Moreover, the recent history of many
breeds is characterized by narrow bottlenecks and population
expansions (Ostrander et al. 2000; Ostrander & Kruglyak
2000), and the existing population of purebred dogs (>300
breeds recognized by both Fe´de´ ration Cynologique
Internationale and the American Kennel Club) may be
described as a collection of partially inbred genetic isolates.
Some of the breed-specific morphological characteristics,
inherited diseases and behaviors are likely to be the result
of pronounced founder effects (Chase et al. 2002; Ostrander
& Kruglyak 2000; Ostrander et al. 2000; Overall 2000).
Since 1989, the Swedish Working Dog Association has
carried out a standardized behavioral test called Dog
Mentality Assessment (DMA), and each year, thousands of
dogs representing more than 180 breeds are being scored in
six test situations called social contact, play, chase, sudden
appearance, metallic noise and ghost. In each test situation,
the animal is presented to a stimulus, and several behavioral
traits are scored simultaneously. Svartberg and Forkman
(2002) used factor analysis to explore the phenotypic correl-
ation structure of DMA test results from a wide array of
breeds and aggregated the scored behavioral traits into
higher order composite traits. However, in animal research
where behavior is assessed across several test situations,
Genes, Brain and Behavior (2006) 5: 240–248 Copyright #Blackwell Munksgaard 2005
240 doi: 10.1111/j.1601-183X.2005.00155.x
the correlation of behavioral traits scored in the same test
situation tend to be larger than the correlation of behavioral
traits scored in different test situations, presumably due to
environmental events that occur just before or during the
test situations. Thus, factor analysis on phenotypic correl-
ations can result in factors mainly discriminating between
test situations, which may obscure less-pronounced cross-
test behavioral consistencies (Henderson et al. 2004).
An alternative way to define higher order behavioral traits
is to use information on the genetic structure of the meas-
ured behavioral responses for the definition of composite
traits (Flint 2003). When the genotype of animals is
unknown, the co-inheritance (or genetic correlation) of two or
more behavioral traits indicates that there are shared genetics
and possibly a common biological mechanism underlying the
behavioral traits. In this study, the genetic correlations
between 16 measured behavioral traits were estimated in a
cohort of DMA-tested German shepherd and Rottweiler dogs,
using the pedigree register kept by the Swedish Kennel Club
(Egenvall et al. 1999). The genetic correlation structure was
compared between the two breeds and to previously defined
personality traits. This data set, containing over 10 000 related
and behaviorally tested dogs, is to our knowledge the largest
data set that has been used for this purpose.
Materials and methods
The Dog Mentality Assessment test
This study is based on German shepherd and Rottweiler
dogs that have been tested in a standardized behavioral
test called DMA by the Swedish Working Dog Association.
They initiated their testing of dogs in 1989, and in September
2001, more than 24 000 dogs from more than 150 breeds
had been tested. The test was originally developed as a tool
for selective breeding of working dogs and is today consid-
ered as a general behavioral test by many breeding clubs in
Sweden. In the test, dogs are exposed to several test situ-
ations, and in each test situation, the intensity of one or more
reactions (behavioral traits) are scored from 1 to 5 by an
official observer, according to a standardized score sheet
(see Supplementary material for details). All functionaries
(observers and test leaders) have been trained and certified
by the Swedish Working Dog Association, and the perform-
ance of the observers has been tested to assure a maximum
of inter-rater reliability.
In 1997, the test was modified, and the number of test
situations, as well as the number of scored behavioral traits,
was expanded. In this study, personality trait scores have
been calculated from the 16 behavioral traits that were
scored in six test situations (social contact, play, chase,
sudden appearance, metallic noise and ghost) that existed
and were similar before and after the revision of the test. The
scoring scale for four of these behavioral traits had been
slightly altered after the revision of tests, and thus, the
score from the earlier version of the test was adjusted to
the intensity scale of the second version (for details see
Strandberg et al. 2005).
Sampling and data preparation
German shepherds and Rottweiler were the two most
numerous breeds, constituting over 50% of all tested dogs.
The sample was restricted to dogs that had a complete score
in all 16 investigated behavioral traits and dogs that had been
scored by a judge that had scored at least 9 other dogs. In
total, 182 official observers (judges) were involved scoring
the dogs for this data set. For the dogs that had been tested
twice, only the results from the first test occasion were
analyzed. Because no more than 10 Rottweiler and nine
German Shepard dogs had been tested more than once,
the repeatability was not estimated. Furthermore, because
the test occasions were typically separated by 12 months or
more for dogs that had been tested twice, the results from a
second test could not be expected to be a good repeated
measure, owing to the possible learning effect and the possibi-
lity of specific training in the intervening period. These criteria
resulted in a sample of 5964 German shepherds and 4589
Rottweilers (Table 1). To estimate the genetic correlations and
heritabilities, untested relatives to the tested dogs were
included to the level of grandparents. As a result, 3646 untested
German shepherds and 1255 untested Rottweiler dogs were
added to the pedigree files including all tested German shep-
herds and Rottweilers respectively. The pedigree information
was retrieved from the registries of the Swedish Kennel Club.
Estimation of genetic correlations and heritability
To estimate the heritability of the 16 scored behavioral traits
and the degree to which they are co-inherited (genetic correl-
ations, R
A
), we analyzed the behavioral traits in all possible pair-
wise combinations with a bivariate variance component model.
This is a mixed linear model in which the column vector of
phenotypic values of nindividuals (y) is expressed in terms of
its additive genetic value and other random and fixed effects:
y¼XbþZaþWcþeð1Þ
where b,a,cand eare vectors of fixed effects, additive
polygenic effect (breeding values), litter effect and residuals,
respectively, with all observations for trait 1 coming first,
followed by all for trait 2, and X,Zand Ware the corres-
ponding design matrices (Henderson 1984; Mrode 1996).
A statistical analysis package (DMU, version 6, release 4)
developed for quantitative genetics analysis (Madsen &
Jensen 2000) was used to fit the models.
The fixed effects included in bwere sex, age at test in
months (12–25), test version (1 or 2), test year (1989–2001),
calendar month of testing (1–12) and judge scoring the dog
(1–182). The expectation of random effects were all zero
with the following distributions:
The genetic contribution to canine personality
Genes, Brain and Behavior (2006) 5: 240–248 241
varðaÞ¼ s2
a1sa1a2
sa2a1s2
a2
A;varðcÞ¼ s2
c1sc1c2
sc2c1s2
c2
Ic
and varðeÞ¼ s2
e1se1e2
se2e1s2
e2
I
where the two traits are indexed by 1 and 2, Ais the additive
relationship matrix including available information on all rela-
tionships among all individuals, and I
c
and Iare identity
matrices of sizes equal to number of litters and observations,
respectively. The genetic correlation was defined as
sa1a2.ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
s2
a1s2
a2
q. The heritability was calculated as
s2
a=ðs2
aþs2
cþs2
eÞ, averaging over all 15 bivariate analyses of
the behavioral variable. The fixed effects included in the
model were selected from a preliminary analysis using a
linear model excluding the additive polygenic and litter
effects with the GLM procedure (Proc GLM) in the SAS soft-
ware (SAS/STAT
Ò
software, version 8.02, SAS institute Inc.,
Cary, NC). Typically, three to five of the six fixed effects
included in the model had a significant influence on the
score of a behavioral trait. The effect of judge was always
highly significant (P<0.0001). For German shepherd, the
effect of sex was significant for 12 of the 16 behavioral traits,
and the effects of age, test, year and month were significant
for 11, 2, 15 and 11 of the 16 behavioral traits, respectively.
For Rottweiler, the effect of sex, age, test, year and month
were significant for 14, 7, 1, 7 and 7 of the 16 behavioral
traits, respectively. For simplicity, the same model was used
for all behavioral traits. The random factors (direct genetic
and litter effects) were selected based on previous model
evaluation of DMA personality traits in German Shepard
(Strandberg et al. 2005).
Analysis of genetic correlation matrix
The significance level of a¼0.01 was chosen for the esti-
mated genetic correlations. Under the null hypothesis, we
expect to find approximately one significant correlation in
each breed by chance, because we are studying 120 genetic
correlations. This corresponds to a false discovery rate of
approximately 0.016 in German shepherd and 0.023 in
Rottweiler. Principal component analysis (Proc Princomp,
SAS/STAT
Ò
software, version 8.02, SAS institute Inc.) was
used to explore the structure of the genetic correlation
matrix. The relative importance of principal components
was assessed with a scree diagram (Cattell 1965).
Evaluation of personality rating model
In previous studies, Svartberg (2002) and Svartberg & Forkman
(2002) used phenotypic correlations to group the behavioral
variables scored in the DMA test into several specific per-
sonality traits and one higher-order personality trait called
Shyness–Boldness. We used five of these predefined com-
posite personality traits (Table 2) to predict the genetic correlation
pattern and compared it to the observed genetic correlation.
For the predictions, it was assumed that the behavioral traits
contributing to a composite personality trait are co-inherited
and that the contribution of each trait is equally strong.
Similarly, it was assumed that behavioral traits that do not
contribute to the same composite personality traits are
Table 1: Background information and population structure of tested German shepherd and Rottweiler dogs
Breed
German shepherd Rottweiler
Total number of tested dogs 5964 4589
Original test (1989–96) 2180 2117
Revised test (1997–2001) 3784 2472
Test age in months 17.2 (14–17) 16.5 (14–17)
Males 3128 2248
Females 2836 2341
Fathers of tested dogs 818 434
Tested fathers 110 151
Tested dogs with tested fathers 863 2051
Mothers of tested dogs 1697 785
Tested mothers 280 343
Tested dogs with tested mothers 1465 2352
Number of litter 2265 1207
Inbred dogs (of tested dogs) 5734 4092
Inbreeding coefficient 2.9% (1.3–4.1) 3.2% (1.0–4.3)
Untested relatives included 3646 1255
Mean and range (first to third quartile) are given for age (in months) and inbreeding coefficient. Inbreeding coefficients are given for inbred
animals only, and the estimates are based on the last 10 generations.
Saetre et al.
242 Genes, Brain and Behavior (2006) 5: 240–248
inherited independently, i.e. are genetically uncorrelated.
Firstly, the genetic correlation pattern was predicted, assuming
the existence of four genetically independent personality traits
(supplementary Table S1). Next, the genetic correlation pattern
was predicted for the higher order trait shyness–boldness, imply-
ing that shared genetics is underlying all behavioral response
except aggressive behavior (supplementary Table S2). The pre-
dicted correlation pattern was fitted to the observed correlation
patterns with a regression model (Proc GLM, SAS/STAT
Ò
software,
version 8.02, SAS institute Inc.) estimating the strength of the
genetic correlations (b
i
). The model fit was assessed with the
fraction of explained to total variation (r
2
).
Results
We estimated the genetic correlation matrix corresponding
to the DMA test for two breeds, German Shepard and
Rottweiler, with a bivariate variance component models
(mixed linear models) for all pair-wise combinations of 16
scored behavioral traits (Table 3). The overall correspond-
ence of genetic correlations between the two breeds was
high, with a r
2
¼0.79, and a slope close to one (Fig. 1).
However, there were some differences between the breeds:
genetic correlations tended to be stronger in German
Shepherd than in Rottweiler, as evident from the average
genetic correlation for each breed (0.53 vs. 0.45, P¼0.01)
and from the number of significant (P0.01) correlations
(77 vs. 53). Specifically, the genetic correlations associated
with following and grabbing in the chase test situation and
with the startle reaction in the metallic noise and the ghost
test situations appeared to be weaker in Rottweiler than in
German shepherds (Table 3).
In both breeds, most of the additive genetic variance under-
lying the correlation matrix could be explained by one under-
lying trait, as revealed by principal component analysis
(Fig. 2a). The first principal component explained 58 and 53%
of the total additive genetic variance of German shepherd and
Rottweiler respectively, and the loadings of behavioral traits on
the first principal component (PC1) were very similar in both
breeds except for aggressive response (Fig. 2b). The average
(absolute) value of loadings on PC1 for all behavioral traits,
except the two associated with aggression, were 0.8 and
0.75 for German shepherd and Rottweiler, respectively.
Behavioral traits associated with playfulness, chase-proneness
and exploration had positive loadings, whereas behavioral
response associated with startle reaction or remaining fear
loaded negatively on the first principal component (Fig. 2b).
The eigenvalues and the variation explained by the remaining
principal components were very small compared with that of
the first component (Fig. 2a), and therefore, higher order
Table 2: Definition of four specific and one broad personality trait created from 16 behavioral traits scored in a standardized behavioral
test for dogs
Specific personality traits
Test situation Scored behavior Playfulness Chase-proneness Curiosity/fearlessness Aggressiveness Boldness
Social contact Greeting 0 0 0 0 þ
Play Interest þ00 0þ
Grabbing þ00 0þ
Tug-of-war þ00 0þ
Chase Following 0 þ00þ
Grabbing 0 þ00þ
Sudden
appearance Startle reaction 0 0 – 0 –
Exploration 0 0 þ0þ
Remaining
avoidance 0 0 – 0 –
Aggression 0 þ0
Metallic noise Startle reaction 0 0 – 0 –
Exploration 0 0 þ0þ
Remaining
avoidance 0 0 – 0 –
Ghost Startle reaction 0 0 – 0 –
Exploration 0 0 þ0þ
Aggression 0 0 0 þ0
Scores for the personality traits are calculated by summing the representative behavioral traits, with a positive or negative sign as indicated in
the table. For details on the calculations, see Svartberg (2002).
The genetic contribution to canine personality
Genes, Brain and Behavior (2006) 5: 240–248 243
Table 3: Genetic correlations between 16 behavioral traits in German shepherd and Rottweiler dogs, estimated from bi-variate variance component models
German shepherds
Test situation Scored behavior 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 Social contact Greeting 0.05
2 Play Interest 0.51* 0.19*
3 Grabbing 0.49 1.00*
,
† 0.14*
4 Tug-of-war 0.44 0.98*
,
† 0.86*
,
† 0.19*
5 Chase Following 0.36 0.70* 0.80* 0.61* 0.06*
6 Grabbing 0.39 0.67* 0.86* 0.70* 0.94*
,
† 0.09*
7 Sudden
appearance
Startle reaction 0.69* 0.32* 0.50* 0.40* 0.24 0.34 0.17*
8 Exploration 0.28 0.48* 0.61* 0.51* 0.26 0.31 0.89*
,
† 0.18*
9 Remaining
avoidance
0.61 0.76* 0.92* 0.64* 0.50 0.62* 0.76*
,
†0.87*
,
† 0.07*
10 Metallic noise Startle reaction 0.45 0.38* 0.45* 0.36* 0.58* 0.50* 0.78*
,
†0.71*
,
† 0.73*
,
† 0.14*
11 Exploration 0.58 0.70* 0.71* 0.58* 0.60* 0.49* 0.72*
,
† 0.87*
,
†0.79*
,
†0.75*
,
† 0.10*
12 Remaining
avoidance
0.45 0.74* 0.92* 0.66* 0.70* 0.72* 0.50*
,
†0.73*
,
† 0.85*
,
† 0.75*
,
†0.89*
,
† 0.07*
13 Ghost Startle reaction 0.29 0.40* 0.39* 0.43* 0.61* 0.46* 0.67*
,
†0.52*
,
† 0.56*
,
† 0.73*
,
†0.60*
,
† 0.25† 0.18*
14 Exploration 0.46 0.57* 0.48* 0.58* 0.68* 0.48* 0.95*
,
† 0.89*
,
†0.80*
,
†0.78*
,
† 0.67*
,
†0.48*
,
†0.77*
,
† 0.11
15 Sudden appearance Aggression 0.13 0.24 0.26 0.22 0.57* 0.35 0.27 0.21 0.03 0.21 0.28 0.12 0.45* 0.11 0.10*
16 Ghost Aggression 0.00
Rottweilers
0.23 0.23 0.27 0.21 0.25 0.35 0.22 0.29 0.29 0.37 0.25 0.31 0.21 0.71*
,
† 0.12*
Test situation Scored behavior 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 Social contact Greeting 0.09*
2 Play Interest 0.55* 0.14*
3 Grabbing 0.57 0.97*
,
† 0.07
4 Tug-of-war 0.72* 0.82*
,
† 0.97*
,
† 0.11*
5 Chase Following 0.07 0.62* 0.67* 0.02 0.10*
6 Grabbing 0.35 0.62* 0.72* 0.32 0.78*
,
† 0.12*
7 Sudden
appearance
Startle reaction 0.38 0.40 0.64* 0.47 0.05 0.32 0.13*
8 Exploration 0.57* 0.67* 0.79* 0.76* 0.35 0.62* 0.69*
,
† 0.10*
9 Remaining
avoidance
0.70* 0.78* 0.95* 0.96* 0.34 0.33 0.69*
,
†0.63*
,
† 0.08*
10 Metallic noise Startle reaction 0.16 0.13 0.25 0.22 0.08 0.00 0.81*
,
†0.28† 0.34† 0.09*
11 Exploration 0.83* 0.71* 0.77* 1.00* 0.37 0.50* 0.49*
,
† 0.84*
,
†0.94*
,
†0.70*
,
† 0.09*
12 Remaining
avoidance
0.54 0.62* 0.76* 0.84* 0.06 0.01 0.34† 0.45† 1.00*
,
† 0.92*
,
†0.85*
,
† 0.04
13 Ghost Startle reaction 0.30 0.27 0.76* 0.27 0.27 0.24 0.48*
,
†0.48*
,
† 0.20† 0.36† 0.38† 0.34† 0.16
14 Exploration 0.58* 0.43* 0.93* 0.52* 0.27 0.33 0.61*
,
† 0.73*
,
†0.38† 0.54*
,
† 0.66*
,
†0.60*
,
†0.88*
,
† 0.14*
15 Sudden appearance Aggression 0.19 0.08 0.24 0.09 0.10 0.27 0.20 0.21 0.22 0.17 0.19 0.23 0.07 0.08 0.10*
16 Ghost Aggression 0.16 0.08 0.11 0.32 0.09 0.14 0.17 0.07 0.29 0.16 0.24 0.14 0.47 0.33 0.52*
,
† 0.06*
Heritabilities are given on the diagonal.
*Statistically significant estimates (P0.01).
†
The grouping of behavioral traits into four previously defined specific personality traits.
Saetre et al.
244 Genes, Brain and Behavior (2006) 5: 240–248
components were not further analyzed. The first principal com-
ponent suggested that there is shared genetics behind all
behavioral traits except in those related to aggression, and
thus, supports the previously defined higher order personality
trait shyness–boldness (Svartberg 2002).
We then specifically studied the genetic correlations of the
behavioral traits that are grouped together in DMA personality
rating system. We noted that the behavioral traits that are used
to calculate the personality trait playfulness (interest, grabbing
and tug-of-war) were all strongly (r
A
>0.8) positively correl-
ated (Table 3). The genetic correlations for the behavioral traits
associated with chase-proneness (following and grabbing) and
aggressiveness (aggression in the sudden appearance and
ghost-test situations) were also positive and statistically sig-
nificant, although the correlations were not strong (Table 3).
For the composite personality trait exploration/fearlessness,
the signs of the genetic correlations between behavioral traits
agreed with expectations from the definition of the trait. That
is, behavioral traits that are summed with equal sign were
positively correlated to each other, whereas behavioral traits
that are summed with different signs were negatively correl-
ated. In German shepherds, all but one of the 28 genetic
correlations associated with exploration/fearlessness were
statistically significant. However, in Rottweiler, one-third of
the correlations were relatively weak (|r
A
|0.45) and not sig-
nificantly different from zero (Table 3). Taken together, the
correlation pattern expected from all four of the specific per-
sonality traits could only explain 46 and 39% of the variation of
observed genetic correlations in German shepherd and
Rottweiler, respectively. However, the predicted correlation
pattern for the broad personality trait shyness–boldness fitted
the observed data much better, and the predicted correlation
pattern from shyness–boldness explained 85 and 77% of the
variation of observed genetic correlations in German shepherd
and Rottweiler, respectively.
The heritability values of the 16 behavioral traits are shown
as the diagonal numbers in Table 3. These values ranged
from 0.04 (remaining fear) to 0.19 (tug-of-war), and the
genetic variance was significantly different from zero for all
but one trait in German shepherd and two traits in
Rottweiler. The heritability of the higher order personality
trait shyness–boldness was higher, 0.25 and 0.27 for
German shepherd and Rottweiler respectively.
Discussion
Behavioral genetic research on personality in dogs was pio-
neered by Scott and Fuller at the Jackson Laboratory in Bar
Harbor (Maine, USA) during the 50s and 60s (Scott & Fuller
1966). They demonstrated a significant genetic contribution
to almost all investigated traits, and by analyzing the behavior
in five dog breeds, several broad behavioral traits were also
identified that were associated with fearfulness, aggressive-
ness, reactivity and general activity (Brace 1961; Cattell &
Korth 1973; Royce 1955). Behavioral testing of dogs is now
widely used in breeding programs around the world, for
example, for selecting service dogs. A standardized behav-
ioral test, the DMA, has been used by Swedish Working Dog
Association since 1989; and each year, thousands of dogs
representing more than 180 breeds are being tested. To
explore to what extent and how behavioral traits are
transmitted between generations, we have estimated herit-
abilities and genetic correlations for behavioral traits in a
cohort containing over 10 000 behaviorally tested German
shepherd and Rottweiler dogs.
Genetic correlations
Rottweiler
German Shepherd
–1.25
–1.00
–0.75
–0.50
–0.25
0.00
0.25
0.50
0.75
1.00
1.25
–1.25 –1.00 –0.75 –0.50 –0.25 0.00 0.25 0.50 0.75 1.00 1.25
Figure 1: Genetic correlations (r
A
)of
16 behavioral traits scored in a stand-
ardized behavioral test for dogs in two
breeds of dogs. The estimate of 120
genetic correlations in Rottweiler is
plotted as a function of the correspond-
ing estimate in German shepherd. The
correspondence of estimates in the two
breeds was high, with a linear regression
slope of 0.98 (SE ¼0.05) and r
2
¼0.79.
The genetic contribution to canine personality
Genes, Brain and Behavior (2006) 5: 240–248 245
In the study, we investigated 16 behavioral traits (vari-
ables) scored in the DMA test in the two breeds of dogs.
It was shown that the reaction in one test situation is not
genetically independent from the reactions in other test
situations. In fact, our analysis provides evidence that there
may be substantial shared genetics underlying most of the
0
1
2
3
4
5
6
7
8
9
10
12345
Principal components
Eigenvalue
Social
contact
Play Chase Sudden
appearance
Metallic
noise
Ghosts
greeting
interest
grabbing
following
tug-of-war
startle reaction
grabbing
exploration
aggression
remain avoidance
remain avoidance
startle reaction
exploration
startle reaction
exploration
aggression
Behavioral variables
PC
1
l
oa
di
ngs
–1.5
–1
–0.5
0
0.5
1
1.5
(a)
(b)
Figure 2: Principal component analysis of the genetic correlation matrix of 16 behavioral traits. (a) The first principal component
(PC1) explains explains 58 and 53% of the total additive genetic variation for German shepherds [black circles (*)] and Rottweilers
[white circles (*)], respectively. Only marginal additional variation is explained by higher order principal components. (b) Loadings of 16
behavioral traits on the first principal component for German shepherds [black rectangles (&)] and Rottweilers [white rectangles (&)].
Loadings have been scaled so that the squared loadings sum up to the eigenvalue of the first component.
Saetre et al.
246 Genes, Brain and Behavior (2006) 5: 240–248
behavioral response in all of the test situations. The excep-
tion to this is aggressive behavior, which is genetically correl-
ated across two test situations but only weakly correlated to
other behavioral traits. We also note that the overall structure
of the genetic correlations is very similar between the two
breeds. For the broad personality trait shyness–boldness, the
expected pattern of co-inheritance was very similar to the
observed pattern of genetic correlations. The predicted cor-
relation pattern explained 85% of the observed correlation in
German shepherds and 77% in Rottweiler. Furthermore,
shyness–boldness was found to explain almost twice as
much of the variation of genetic correlations as the four
genetically independent personality traits playfulness,
chase-proneness, curiosity/fearlessness and aggressive-
ness. The existence of a partly genetically determined
broad behavioral trait that can explain a significant part of
the behavioral response in all the test situations, with the
exception of aggressive behavior, is further strengthened by
the fact that the heritability estimates of boldness (0.25 and
0.27) exceeded those of the individual behavioral traits in
both breeds (0.04–0.19).
The DMA test has been designed to meet the demands
from breeders of working dogs, and the resulting data cannot
be regarded as direct observational data in a strict sense. For
example, recording a behavioral response in a five-point
intensity scale is obviously a crude and over-simplified
description of underlying behavioral responses that clearly
depends on the description of the intensity scale. However,
the collected data comprise a much larger number of dogs
than would ever be possible to test under more strict condi-
tions. The behavioral scores derived from DMA personality
rating have also been shown to have a high test–retest
consistency (Svartberg et al. 2005a) and a good predictive
power for behaviors outside the test situation and for perform-
ance in working dog trials (Svartberg 2002; Svartberg 2005b).
Also, in spite of using crude test methods, general tests
measuring similar aspects of dog personality still contribute
to our knowledge about basic patterns in dog behavior and
have proved to be useful in the selection of potential working
dogs (Wilsson & Sundgren 1997).
There are several previous studies indicating the existence
of a broad personality trait in dog similar to the shyness–
boldness dimension. For example, Brace in Scott and Fuller
(1966) identified one general behavioral dimension related to
activity, confidence and performance in several test situ-
ations. This personality trait was labeled ‘Activity–success’
and was uncorrelated to aggressive behavior. Goddard and
Beilharz (1985) studied the social behavior of dogs and iden-
tified a personality trait that was labeled ‘Confidence’, which
was uncorrelated to aggression–dominance behavior.
Wilsson and Sundgren (1997) identified a personality trait
associated with courage, nerve stability and hardness across
several different test situations that was only weakly correl-
ated to aggressive behavior (sharpness) and defense drive in
German shepherds and Labrador retrievers. Finally,
Svartberg and Forkman (2002) using similar data as in this
study identified the broad personality trait boldness, which
was stable across a large number of breeds and unrelated to
aggressiveness. We also note that Svartberg has shown that
DMA boldness scores are related to performance in working
dog trials, suggesting that the broad personality trait predis-
poses trainability in general (Svartberg 2002) and that bold-
ness scores can predict behavioral response in the home
environment, including interest in playing with humans,
behavior towards strangers and non-social fear (Svartberg
2005b).
Shyness–Boldness is a personality dimension that is also
readily recognized in humans (Kagan et al. 1988; Matthews &
Deary 1998; Zuckerman 1991) as well as in other mammals
such as rats (Pellis & McKenna 1992), hyenas (Gosling 1998)
and marmots (Armitage 1986). There are also indications that
the shyness–boldness continuum exists in the dog’s wild
ancestor, the wolf (Fox 1972). It has been suggested that
\variation in boldness and shyness can be maintained in a
population by frequency-dependent selection, in which the
relative frequency of bold (risk-prone) phenotypes is depend-
ent on the relative frequency of shy (risk-averse) phenotypes in
a population (Wilson et al. 1994). The fact that the shyness–
boldness dimension has been found in a large number of
breeds (Svartberg & Forkman 2002) and has a clear genetic
basis in the two investigated breeds in this study supports the
previous suggestion that this trait has survived the varied
selection pressures encountered during domestication.
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Acknowledgments
We are thankful to professor Nancy Pedersen, professor Dietrich
von Rosen, Dr Patrik Magnusson and Dr Kenth Svartberg for
valuable comments on the manuscript and to Dr Lennart
Swensson for help with database accession. We would also
like to thank Alexander Santillio for a preliminary genetic analysis
of this material. This work was supported by a strategic grant
from the Swedish University of Agricultural Sciences, the
Swedish Research Council, the Erik Philip-So¨ rensen foundation,
the Beijer foundation, the Marcus Borgstro¨ m Foundation and the
Magnus Bergvalls Foundation.
Supplementary material
The following material is available online at www.blackwell-
synergy.com
Table S1: (A) Genetic correlation pattern predicted from a model
assuming four genetically independent personality traits.
(B) Genetic correlation pattern predicted from a boldness model,
assuming that all behavioral response, except aggressive beha-
vior, is co-inherited.
Appendix S1: Supplementary methods.
Saetre et al.
248 Genes, Brain and Behavior (2006) 5: 240–248
