“We could see that, on average, the working dogs showed less fear, more curiosity and were able to socialize well with humans,” said Åke Hedhammar, professor emeritus at the Swedish University of Agricultural Sciences.
That temperament gap sits at the heart of a genetic study published in Animal Genetics by researchers at Uppsala University, the Swedish University of Agricultural Sciences, the Swedish Armed Forces, and the Broad Institute of MIT and Harvard. The new Swedish study examined how breeding has split German Shepherds into two distinct groups since the breed first appeared in Germany in the late 1800s.
Working Lines and Show Lines Diverge in DNA
By 1909, dogs bred for work already looked different from those bred for shows. Show dogs are primarily bred for physical appearance, featuring a sloping back and angled legs. Working dogs, meanwhile, are bred for tasks and operational skills, and all police and military working dogs belong to this functional group.
To investigate whether those physical split lines extend into behavior and genetics, researchers analyzed data from 23,109 German Shepherds registered with the Swedish Kennel Club. Every animal had completed the Dog Mentality Assessment (DMA), a standardized behavioral test. The test guides each dog and handler through situations, which include a play invitation, threatening ghost-like figures, handling by a stranger, and a sudden startle.
Trained raters score 33 behaviors from 1 to 5 without any pass-or-fail grading. Analysis of those records confirmed six personality traits: sociability, playfulness, chase-proneness, distance playfulness, curiosity/fearlessness, and aggressiveness. While aggressiveness stood apart, the other five clustered into a broader trait known as boldness, which researchers liken to the reverse of neuroticism in humans.
A previous study published in 2006 by Saetre and colleagues in Genes, Brain and Behavior put the heritability of boldness in German Shepherds at 0.25, indicating that about a quarter of the variation stems from genetic differences.
Blood Samples Reveal Chromosome Variations
Following the behavioral analysis, researchers gathered blood samples from 373 dogs that had completed the DMA tests to map their genomes. The cohort comprised 222 working dogs, 132 show dogs, and 19 dogs falling between the two categories. All Swedish show champions belonged to the show group, while every police and military dog populated the working cluster.
“We could then see that there were areas in the genome where differences could be seen in the dogs depending on how curious or playful they were, for example. That meant that we were able to identify some of the genes in working dogs that are linked to curiosity and playfulness,” said Kerstin Lindblad-Toh, professor of comparative genomics at Uppsala University and one of the study's leaders.
The most prominent genetic variation appeared on chromosome 24, which contains genes tied to coat color.
Kerstin Lindblad-Toh, professor of comparative genomics at Uppsala University and one of the study’s leaders, explained the underlying selection pressure during a recent profile reported by Popular Science.
Breeders of working dogs have selected and bred the ones that really enjoy working; it’s a bit like a game for them. It’s interesting that we can now see that this selective breeding has indeed led to differences between working dogs and show dogs among German Shepherds – differences that can be seen at both the behavioral and genetic levels.
Kerstin Lindblad-Toh, Professor of Comparative Genomics at Uppsala University
Shared Genetic Links Between Dogs and Humans
Testing across the genome for links to 40 traits and behaviors revealed at least one significant association for 28 of them. The strongest behavioral signals emerged from chromosome 1 in and near the TCF4 gene, whose protein regulates the activity of other genes involved in brain development. In show dogs, that chromosomal region linked to boldness, distance playfulness, and tug-of-war. In human studies, similar genes have been associated with neuroticism.
For working dogs, recovery time after a frightening experience tied to a region on chromosome 15 near the ELAVL4 gene.
It’s interesting that several of the genes that we identified as influencing behavior in German Shepherds are also linked to that behavior in humans. So we now have an example of how we might also acquire more knowledge about different behaviors in people with help of dogs in the long term.
Kerstin Lindblad-Toh, Professor of Comparative Genomics at Uppsala University
Partnerships Aims for Larger Breeding Trials
While the study connects genes to dog behavior, the authors caution that it does not establish direct cause and effect. The genetic analysis included 373 animals with limited information regarding their individual training backgrounds. A separate survey of 163 breeders covering 4,131 dogs also linked show-focused breeding goals to lower boldness scores.
To build on these results, researchers are collaborating with the Swedish Armed Forces to plan larger independent studies with expanded groups of dogs.
That would ultimately mean that these findings could be used to select which dogs have the best prospects of becoming good working dogs and which could be used in breeding. But we are not there yet. This study is just a first step and shows that there are actually clear differences in behavior between working German Shepherd dogs and German Shepherd show dogs.
Åke Hedhammar, Professor Emeritus at the Swedish University of Agricultural Sciences
The research provides a foundation for understanding how personality traits and boldness scores might distinguish between these two specific types of German Shepherd dogs.
