Genes, Environment & Behaviour: Why a Dog Is More Than Its DNA
Why does one puppy grow into a confident, adaptable adult while another becomes more cautious? Why can two littermates, raised in the same household, develop quite different personalities? And when a dog develops a behavioural problem, how do we know whether we are seeing genetics, experience, learning, or some combination of all three?
The answer is not found in the familiar argument of “nature versus nurture”.
Behaviour is the product of their interaction.
A dog's genes provide biological influences that affect how its nervous system develops, how it perceives and responds to stimuli, and its predispositions towards particular behavioural tendencies. Its environment then provides the experiences through which those predispositions are expressed, modified and learned.
Understanding this relationship is fundamental to understanding dogs.
Genes influence behaviour, but they do not provide a behavioural script
A dog's genome contains biological instructions that influence the development and functioning of the brain, sensory systems, endocrine system and other physiological processes involved in behaviour.
Selective breeding has made the genetic contribution to canine behaviour particularly obvious. Dogs have been bred for generations for behaviours associated with herding, hunting, retrieving, pointing, guarding, tracking and other specialised tasks. The remarkable behavioural diversity between breeds could not be explained by training alone.
But it would be a mistake to interpret this as meaning that a particular behaviour is simply “in the genes”.
Most behavioural characteristics are complex traits. They are influenced by many genetic variants, each potentially contributing a relatively small effect, alongside environmental influences and learning. Research into canine behavioural genetics has consistently demonstrated both genetic and environmental contributions, while also highlighting how difficult it is to measure behaviour and separate these influences accurately.
A dog may therefore inherit a predisposition towards heightened responsiveness, persistence, sociability, environmental sensitivity or particular working behaviours without inheriting a predetermined outcome.
Genes influence the starting point.
They do not dictate the entire journey.
Heritability does not mean inevitability
One of the most misunderstood concepts in discussions about behaviour is heritability.
If a behavioural characteristic is described as heritable, that does not mean that a particular percentage of an individual dog's behaviour is “genetic”. Heritability is a population statistic describing how much of the observed variation in a particular trait, within a particular population and environment, can be attributed to genetic differences.
It cannot tell us that an individual dog is, for example, “60% genetic”.
This distinction is important because behavioural traits are particularly dependent on context. A dog's behaviour can change substantially as it learns, matures and encounters different environments.
A 2015 meta-analysis of canine behavioural traits found generally low heritability across the behavioural categories examined, while also acknowledging the considerable methodological challenges involved in measuring complex behaviour. More recent genomic research has continued to demonstrate that canine behaviour has genetic contributions, but that these contributions are complex and interact with environmental experience.
This is why responsible breeding cannot simply rely on a single temperament test or assume that a particular behavioural characteristic will be passed directly from parent to puppy.
Behavioural genetics is much more complicated than that.
Environment provides the experiences
If genes influence the biological potential for behaviour, the environment provides the circumstances in which that potential develops.
For a puppy, environment begins before birth and continues throughout life.
Maternal environment, early development, nutrition, physical health, sensory experiences, social experiences, housing, handling, learning opportunities, stress, training and relationships with humans can all contribute to behavioural development.
The puppy's experiences do not simply add information to an otherwise fixed brain. The developing nervous system is continually changing in response to experience.
This is why early life matters.
Research into canine socialisation indicates that early experience is associated with later behavioural outcomes, although the scientific literature also shows that the details of effective socialisation are more complicated than simply exposing puppies to as many things as possible. Timing, quality, intensity and the puppy's individual response all matter.
A puppy does not need a catalogue of experiences.
It needs appropriate experiences from which it can learn.
The same environment does not produce the same dog
This is where the relationship between genes and environment becomes particularly interesting.
Imagine two puppies growing up in the same household. They eat the same food, sleep in the same room, meet the same people and experience the same training.
They can still behave differently.
Why?
Because they are not genetically identical, and they do not necessarily perceive or respond to the same experience in the same way.
One puppy may find a new environment exciting. Another may find it overwhelming. One may recover almost immediately from a startling noise. Another may remain cautious for longer.
Their experiences are therefore not actually identical from a behavioural perspective.
The environment acts upon an individual nervous system, and the individual's characteristics influence how that environment is experienced.
This is one of the reasons that describing behaviour as simply “genetic” or “environmental” is inadequate.
Gene–environment interaction
Scientists use the term gene–environment interaction to describe situations in which genetic differences influence how individuals respond to environmental conditions.
Two dogs can encounter the same event but respond differently because their biological characteristics differ.
Conversely, the same genetic predisposition may produce different outcomes under different environmental conditions.
This is particularly relevant to behavioural traits involving fear, stress responsiveness, aggression, sociability and working behaviour. Contemporary canine behavioural research increasingly recognises that these characteristics cannot be understood properly by examining genes or environment in isolation.
Consider a puppy with a relatively sensitive temperament.
That sensitivity is not automatically a problem.
In an appropriate environment, the puppy may learn that unfamiliar things can be approached gradually, that retreat is available when needed, and that their human provides predictable support. The same underlying sensitivity may contribute to careful observation, environmental awareness and thoughtful decision-making.
In a chronically overwhelming or unpredictable environment, however, that same sensitivity may contribute to stronger fear responses or difficulty coping.
The genetic predisposition has not changed.
The developmental context has.
Learning changes behaviour
Environment is not simply about what happens to a dog. It is also about what the dog learns from what happens.
Every interaction provides information.
If barking makes an unfamiliar person move away, barking may become more likely in that situation.
If remaining calm results in access to something rewarding, calm behaviour may become more likely.
If approaching a novel object produces something unpleasant, avoidance may become more likely.
Through learning, behaviour is continually being modified.
This means that a dog's current behaviour cannot necessarily tell us what its original genetic predisposition was. A behaviour we see in an adult dog may be the result of an interaction between temperament, previous experiences, reinforcement history, learning, maturation and current circumstances.
Research into canine executive functions similarly indicates that early experience, training, housing and stress can influence the development of behavioural regulation and cognitive skills. Importantly, the evidence suggests that manageable challenges can support development, whereas excessive stress can have detrimental effects.
Behaviour can change without changing the genes
This is an important point for anyone living with or raising a dog.
A dog does not need to have a different genetic makeup to behave differently.
Learning can change behaviour.
Maturation can change behaviour.
Experience can change behaviour.
Changes in health can change behaviour.
Changes in environment can change behaviour.
A dog that was highly excitable as a puppy may become much better at regulating its behaviour with maturity and appropriate learning. A confident dog may develop fear following a frightening experience. A dog that was comfortable around other dogs may become selective after repeated negative encounters.
The genes have not suddenly changed.
The dog's history has.
This is why behaviour should be understood developmentally rather than judged as a permanent characteristic based on a single observation.
What about epigenetics?
The relationship between genes and environment becomes even more interesting when we consider epigenetics.
Epigenetic mechanisms influence how genes are expressed without changing the underlying DNA sequence.
Environmental experiences can influence molecular processes involved in gene regulation, and this is one mechanism through which experience can interact with biological development. Current research is investigating these processes across animal behaviour, including how experiences can influence developmental pathways.
Epigenetics is sometimes presented online as though an experience simply “turns a gene on or off” and permanently changes an animal's behaviour. That is an oversimplification.
Epigenetic regulation is complex, tissue-specific and dependent on biological context. Evidence for particular behavioural effects, and especially for effects being reliably transmitted across generations, varies considerably.
It is an important area of research, but it should not be used as a catch-all explanation for behavioural differences.
What this means for breeders
Understanding genes and environment has profound implications for breeding.
Breeding determines much more than physical appearance. Selection can influence behavioural tendencies as well.
The goal, however, should not be to produce puppies with identical personalities.
A healthy breeding program should consider the behavioural characteristics that are appropriate for the breed's purpose and for the lives the puppies are likely to lead. Parents' behavioural history, temperament, working characteristics and responses to everyday environments can all provide useful information alongside health and physical traits.
But genetics is only one part of the equation.
Breeders also have responsibility for the developmental environment they provide.
The prenatal environment, maternal care, early handling, sensory experiences, opportunities for appropriate exploration, social experiences, recovery from mild challenges and the quality of the transition into the puppy's new home can all contribute to development.
Good breeding therefore does not end with selecting the parents.
And good puppy raising does not compensate for poor genetic selection.
Both matter.
What this means for puppy owners
Perhaps the most useful message is that your puppy is neither a blank slate nor a finished product.
They arrive with individual biological characteristics and predispositions. You cannot train every puppy into exactly the same temperament, and you cannot prevent every behavioural difficulty simply by providing perfect experiences.
But neither are you powerless.
The environment you provide matters.
The experiences you choose matter.
The way you respond to your puppy's behaviour matters.
The opportunities you provide for exploration, learning, recovery and successful problem-solving matter.
So, when a puppy behaves differently from another puppy, the answer is rarely as simple as “that's genetic” or “you didn't socialise them properly”.
It may be genetics.
It may be environment.
It may be learning.
It may be maturation.
It may be health.
And very often, it is an interaction between several of these factors.
There is no nature versus nurture
The old question of whether behaviour is determined by nature or nurture is therefore the wrong question.
Nature and nurture are not competing explanations. They are interacting biological processes.
Genes influence how a dog develops and responds to its environment. The environment influences development, learning and behaviour. Experience can alter the way biological systems function, while an individual's inherited characteristics influence how those experiences are perceived and processed.
The dog in front of us is the result of all of these influences interacting over time.
That is why two puppies from the same litter can become remarkably different dogs.
It is why a genetically predisposed behaviour can be expressed differently in different environments.
It is why early experiences matter without determining everything.
And it is why responsible breeding and thoughtful raising belong together.
We cannot choose a puppy's genes or control everything they will encounter throughout life. But we can make informed decisions about both the genetics we breed from and the environments in which puppies learn to navigate the world.
That is where science moves us beyond the simplistic nature-versus-nurture debate and towards a much more useful understanding of canine behaviour: genes provide possibilities; experience helps shape how those possibilities are expressed. Donna Williams,
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