Genetics vs. Environment in Dogs: What Fifty Years of Breeding Taught Me Before I Read Pfaffenberger
- Maria Cecilia Martinez
- Jul 31
- 16 min read
I Did Not Discover This Philosophy in a Book
For more than fifty years, I have lived surrounded by dogs.
I have not simply owned them. I have watched thousands of puppies take their first breaths. I have watched generations of German Shepherds mature into working dogs, police dogs, service dogs, champions, family protectors, and deeply loved companions.
Long before I knew the scientific language behind genetics vs environment in dogs, the dogs themselves were teaching me.
Some puppies arrived in this world carrying a natural boldness that could be seen before most people would believe temperament could be seen at all. Some possessed tremendous drive. Some watched everything. Some recovered from surprise almost immediately, while others stopped, studied the situation, and needed more time before moving forward.
These were not puppies that had already been trained.
These differences were present from the beginning.
But I also witnessed something equally important.
A puppy could be born with remarkable possibilities and still fail to reach them.
Natural confidence could weaken when a puppy was sheltered from the world. Curiosity could be discouraged. Recovery could become slower. A genetically capable puppy could learn hesitation if every unfamiliar experience was either avoided or handled badly.
The opposite was also true.
A thoughtful developmental environment could help a puppy use the abilities already living inside him. It could teach him how to investigate uncertainty, recover from surprise, trust his own body, and look toward a human being for guidance.
Long before I opened a book written by Clarence J. Pfaffenberger, these observations had quietly shaped my breeding and puppy-development philosophy.
Then I read his work.
And I smiled.
Page after page, I found scientific observations that felt strangely familiar. Pfeiffenberger was describing principles my dogs had been demonstrating before my eyes for decades.
This was not the discovery of a new philosophy.
It was the moment science gave language to what a lifetime of dogs had already taught me.
Who Was Clarence J. Pfaffenberger, and Why Does His Research Still Matter?
Clarence J. Pfaffenberger was a researcher, author, and influential figure in the development and selection of guide dogs. His work was associated with the breeding and research program at Guide Dogs for the Blind and drew heavily from the pioneering behavioral studies conducted by John Paul Scott and John L. Fuller.
Pfaffenberger studied a very practical problem: Why did some carefully bred dogs succeed in demanding guide work while others did not?
A guide dog cannot succeed through obedience alone. The dog must possess suitable health, temperament, emotional stability, learning ability, environmental confidence, and the capacity to make decisions under pressure.
Researchers could not solve the problem by looking only at training.
They had to examine the entire dog:
The parents selected for breeding
The puppy’s inherited tendencies
Maternal care
Early human interaction
Developmental timing
Environmental experience
The puppy raiser
Training
Physical health
The dog’s ability to recover from stress
Pfaffenberger helped bring these ideas beyond laboratories and institutional breeding programs. His books, including The New Knowledge of Dog Behavior and Guide Dogs for the Blind: Their Selection, Development, and Training, helped breeders and trainers understand that puppy development occurs through a continuous interaction between inheritance and experience.
Some of the terminology and developmental timelines used in early canine research have since been refined. Science should never be frozen in time. But the central principle remains powerful:
A dog’s eventual behavior cannot be understood by examining genetics or environment in isolation.
The Question Every Breeder Eventually Asks
Are Great Dogs Born—or Are They Made?
People want a simple answer.
Some say, “It is all genetics.”
Others say, “Any dog can become anything if you socialize and train him correctly.”
Both positions are wrong.
Dogs are not blank pieces of paper waiting for humans to write upon them. They arrive carrying biological tendencies inherited through generations.
But they are not finished products at birth either.
A puppy inherits possibilities, sensitivities, limitations, physical characteristics, and behavioral predispositions. Developmental experience then interacts with those inherited characteristics.
That interaction is what makes the old argument about “nature versus nurture” so misleading.
Nature and nurture are not opponents fighting for control of the dog. They work together from the beginning.
The more accurate question is:
How does this individual puppy’s environment influence the possibilities and limitations created by his genetics?
That question is more complicated, but it is also more honest.
Genetics vs Environment in Dogs: What Genetics Really Contribute
Genetics do not create a rigid behavioral destiny. Behavior is complex, and most behavioral traits are influenced by many genes as well as environmental factors.
Nevertheless, inherited differences are real.
Research has identified meaningful heritable components in canine behavioral traits, while also showing enormous variation among individual dogs—even within the same breed.
A large 2022 genomic study found that ancestry helps explain some behavioral tendencies, but breed alone is a poor predictor of an individual dog’s complete personality.
This does not mean breed or bloodline is irrelevant. It means responsible breeders must look much deeper than a breed label.
Temperament
Temperament is not a single gene and it is not one behavior.
It includes patterns of emotional response, sociability, curiosity, sensitivity, persistence, defensiveness, and adaptability.
Genetics help establish the ranges within which these qualities may develop.
A puppy may be naturally social, naturally reserved, highly observant, environmentally bold, or more sensitive to novelty.
Development can influence how those tendencies are expressed, but it cannot pretend they were never there.
Nerve Strength and Emotional Stability
“Strong nerves” is an expression dog people have used for generations. Scientifically, we may discuss emotional reactivity, fearfulness, arousal, resilience, and stress recovery.
Whatever language we use, the practical question remains:
What happens inside this dog when the world becomes uncertain?
Does the dog investigate? Freeze? Avoid? Escalate? Recover? Seek information from the handler?
A dog with solid inherited emotional stability generally has a stronger foundation from which to learn. A more sensitive dog may still develop beautifully, but that puppy’s program must respect his individual threshold.
Exposure cannot be used to beat sensitivity out of a dog.
Drives and Motivation
Food motivation, prey interest, social engagement, persistence, play, possession, tracking interest, and willingness to work with a person vary among dogs.
Training can channel and strengthen useful motivation, but it cannot reliably manufacture deep working drive where little biological capacity exists.
A trainer can awaken and organize what is present.
A trainer cannot order genetics to provide what was never inherited.
Learning Capacity
Dogs differ in attention, persistence, impulse control, problem-solving style, memory, and willingness to repeat an activity.
Learning ability should not be confused with compliance. A highly intelligent dog may question, improvise, or resist repetitive work.
Another dog may be extraordinarily cooperative but less independent in problem-solving.
The correct dog depends on the work expected of him.
Health and Structural Soundness
Behavior never exists separately from the body.
Pain, orthopedic instability, impaired movement, gastrointestinal disease, endocrine disorders, neurological problems, and chronic discomfort can affect behavior and learning.
For working dogs and German Shepherds, structure is not cosmetic.
The dog must be physically capable of doing what his mind is being asked to do.
Selecting for health, functional structure, and longevity is therefore part of behavioral and developmental planning.
Recovery From Stress
A startling event is not the entire test of a dog.
Recovery matters.
When an umbrella opens, a surface shifts, something falls, or an unfamiliar sound occurs, I watch what happens next.
Does the puppy remain trapped in the reaction? Does he flee without returning? Does he pause and then investigate? Does he look to the handler? Can curiosity replace uncertainty?
That transition—from reaction to investigation—is where some of the most valuable information appears.
Genetics influence the nervous system the puppy brings into the situation. Development influences what the puppy learns to do with that nervous system.
What Environment Actually Changes
If genetics establish a range of possibilities, environment influences which possibilities are practiced, strengthened, inhibited, or left undeveloped.
Environment includes far more than “socialization.”
It begins with the physical and emotional condition of the mother, continues through birth and maternal care, and expands through handling, play, surfaces, sounds, movement, novelty, training, relationships, and daily life.
Maternal Care
The mother is a puppy’s first environment.
Her nursing, licking, physical contact, responsiveness, play, corrections, and general behavior all become part of early development.
A study involving German Shepherds in a Swedish military working-dog breeding program found consistent differences in maternal-care styles.
Those differences were associated with aspects of the offspring’s behavior when tested later as adults.
This does not mean “more maternal care is always better” in every circumstance.
Maternal effects are complex, and different styles may influence different outcomes. It means the dam is not merely a source of milk.
She is an active developmental influence.
Human Interaction
Appropriate human contact can build familiarity, trust, social engagement, and willingness to seek guidance.
But the word “appropriate” matters.
Handling should not mean passing helpless puppies around endlessly for human entertainment. Exposure should be developmentally suitable, clean, controlled, and respectful of the mother and puppies.
The purpose is not to overwhelm the puppy with human attention. It is to allow human scent, touch, voice, movement, and presence to become safe and meaningful parts of his developing world.
Environmental Exposure
Surfaces, sounds, objects, textures, movement, mild instability, visual changes, and unfamiliar spaces provide information to the developing nervous system.
At Southernwind, this may include tarps, shallow pools, changing footing, tunnels, raised or moving surfaces, bottles containing pebbles, umbrellas, natural ranch sounds, carefully selected obstacles, and many ordinary objects that move, sound, or feel different.
The objective is not to frighten puppies.
It is to present manageable questions.
“What is this?”
“Can I approach it?”
“What happens when it moves?”
“Can I use my body here?”
“Can I recover when something surprises me?”
The developmental value is not found in the object itself. A tarp is only a tarp.
The value lies in the puppy’s opportunity to notice uncertainty, gather information, act, and recover without being forced beyond his capacity.
Habituation Is Not Flooding
Habituation occurs when repeated or controlled exposure reduces unnecessary response to a stimulus that proves harmless.
Flooding is different. Flooding traps an animal in an intense or frightening situation without adequate ability to escape or regulate the experience.
These should never be confused.
A puppy frozen in place is not necessarily “getting used to it.” He may be overwhelmed.
Good exposure watches the puppy—not the checklist.
The breeder must observe posture, movement, curiosity, avoidance, recovery, and willingness to re-engage. The intensity should be reduced when the puppy cannot process the situation.
Purposeful development builds capacity.
Overwhelming exposure can build fear.
Where Genetics and Environment Meet
This is the point at which the Southernwind Developmental Exposure Protocol™ becomes relevant.
The Southernwind Developmental Exposure Protocol™ did not begin as a commercial program or a fashionable puppy curriculum. It grew gradually through decades of breeding, raising working dogs, training horses, and helping prepare Mounted Police horses and dogs to function around movement, pressure, noise, uncertainty, and real environments.
The principle is simple:
We do not expose puppies merely so they can encounter more things. We create carefully graduated experiences that allow each puppy to practice curiosity, physical awareness, recovery, engagement, and trust.
A confident puppy may walk directly toward a moving object.
Another may stop, watch, circle, and approach from the side.
The goal is not to make those puppies perform identically. The goal is to learn who each puppy is and help each one progress without erasing his individuality.
This is also why developmental exposure can never replace genetic selection.
If a puppy has inherited weak recovery, extreme sensitivity, or unstable responses, placing him around dozens of objects will not rewrite his biological foundation.
It may improve coping. It may broaden experience. It may help the puppy function more successfully.
But development is not magic, and honest breeders should never present it that way.
Watch the Protocol in Practice
Watch Southernwind puppies participating in the Southernwind Developmental Exposure Protocol™ and see how carefully planned experiences encourage curiosity, confidence, body awareness, and recovery.
The Southernwind Four Pillars of Canine Development™
Pillar I: Purposeful Genetics
Select parents for far more than color, titles, or appearance.
Study:
Temperament
Health
Functional structure
Working ability
Social stability
Environmental confidence
Recovery from stress
Instincts and drives
Pedigree patterns
Longevity
Previous offspring
Pillar II: Prenatal and Early Development
Development does not begin when the puppy’s eyes open.
It includes:
The mother’s health and physical condition
Nutrition and veterinary care
Avoidance of unnecessary stress
The whelping environment
Neonatal observation
Gentle, appropriate human interaction
Health, sanitation, sleep, and physical growth
Pillar III: Progressive Environmental Exposure
Experiences should be:
Age appropriate
Gradual
Purposeful
Observable
Varied
Safe
Adapted to the individual puppy
Stopped or modified before the puppy becomes overwhelmed
Pillar IV: Owner Continuation Throughout Life
A breeder cannot complete a dog in eight weeks.
The owner must continue:
Safe environmental exposure
Appropriate social experiences
Training and boundaries
Physical conditioning
Mental work
Confidence-building activities
Veterinary care
Relationship development
Calm leadership
Protection from overwhelming or uncontrolled situations
The breeder lays the foundation.
The owner lives with—and continues building—the dog.
Many people believe puppy development begins at birth.
It does not.
It begins before conception.
When a breeder selects two dogs, that breeder is already making decisions about the potential nervous systems, bodies, health, drives, and behavioral tendencies of puppies that do not yet exist.
No mating is genetically perfect. Every dog carries strengths, weaknesses, and unknowns.
Responsible breeding is not the search for flawless dogs. It is the disciplined study of what each dog may contribute—and whether those contributions serve the future welfare and purpose of the puppies.
This is why responsible German Shepherd breeding must preserve more than a beautiful outline or fashionable color.
It must protect the qualities that allow the dog to live successfully inside his own mind and body.
Selecting parents is not separate from puppy development.
It is the first and perhaps most consequential developmental decision a breeder makes.
The Mistake Many Puppy Owners Make
One of the most common statements I hear is:
“I will socialize him, so he will be fine.”
Socialization is essential, but it has limits.
Socialization cannot guarantee that a genetically fearful dog will become environmentally powerful. It cannot create working drives that are absent. It cannot repair poor structure. It cannot ensure stable aggression thresholds. It cannot convert every puppy into a police dog, service dog, protection dog, or effortless family companion.
Socialization develops the dog who is there.
It does not manufacture an entirely different dog.
The opposite mistake is equally dangerous:
“He comes from excellent genetics, so nothing will bother him.”
Good genetics can also be wasted.
A well-bred puppy who is isolated, mishandled, chronically overwhelmed, deprived of appropriate experience, or allowed to rehearse uncontrolled behavior may never reach his potential.
Good breeding is a beginning—not an excuse to neglect development.
What Modern Science Has Added Since Pfaffenberger
Pfaffenberger helped popularize a developmental way of understanding dogs. Modern science has added powerful tools and important nuance.
Behavioral Genetics
We now understand more clearly that behavior is typically polygenic: influenced by many genetic variants rather than controlled by one simple “temperament gene.”
Genetic influence is also probabilistic, not absolute.
A heritability estimate describes variation within a studied population. It does not tell us what percentage of an individual dog’s behavior is “genetic,” and it does not predict that dog’s destiny.
Gene–Environment Interaction
Dogs with different genetic sensitivities may respond differently to the same environment.
An experience that barely registers in one puppy may have a substantial effect on another. This is why identical exposure protocols should never be applied mechanically to every puppy.
The program may be structured.
The puppy’s response must still guide the human.
Epigenetics
Epigenetics examines biological processes that influence gene activity without changing the underlying DNA sequence.
This field offers important ways to study how nutrition, stress, development, and other environmental conditions may affect gene regulation. However, canine behavioral epigenetics remains an emerging area.
We should not claim that a particular exercise “switches on the confidence gene.” That is not established science.
The responsible conclusion is that inheritance involves more than a simple list of genes, and developmental conditions may influence how biological systems function.
Prenatal Influences and Stress Physiology
Research across mammals shows that prenatal conditions can influence developing stress-regulation systems. In dogs, maternal health, stress, nutrition, disease, and environmental conditions deserve careful attention, although many precise cause-and-effect relationships still require stronger canine-specific research.
A pregnant female should not be treated like an incubator.
Her welfare is part of the puppies’ developmental environment.
Neuroplasticity
The young nervous system changes through experience. Neural pathways involved in movement, learning, emotional regulation, and sensory processing develop through an interaction of biological maturation and experience.
Neuroplasticity does not mean the brain can be shaped into anything.
It means experience changes the developing system within biological limits.
Maternal Behavior
Modern studies confirm that maternal style varies and that these differences can be associated with later behavior.
This supports what experienced breeders have always known: the dam’s temperament and maternal behavior deserve close observation—not only during whelping, but throughout the weeks she raises her litter.
Environmental Enrichment
Scientific reviews indicate that environmental enrichment can support canine welfare, encourage a broader behavioral repertoire, and reduce stress or abnormal behavior in some settings.
But more objects do not automatically create better development.
Quality, timing, safety, individual response, and human judgment matter more than filling a puppy area with equipment for photographs.
The Microbiome
The gut microbiome is involved in digestion, immune function, and communication between the gastrointestinal and nervous systems.
Researchers are investigating relationships between the microbiome, stress, health, and behavior.
This is promising science, but it is not yet responsible to diagnose temperament through a stool sample or claim that a supplement can build courage.
The microbiome should be presented as an important developing field—not as a proven explanation for every behavioral problem.
Practical Guidance for Breeders
A breeder should:
Select parents through long-term knowledge, not appearance alone.
Observe temperament in ordinary life as well as formal testing.
Protect the physical and emotional welfare of the pregnant female.
Study maternal behavior after birth.
Introduce human contact appropriately.
Provide developmentally suitable novelty.
Observe individual responses rather than forcing identical performance.
Distinguish temporary uncertainty from sustained fear.
Allow puppies opportunities to recover and investigate.
Match puppies to homes according to temperament and purpose.
Educate owners about continuing development.
Record outcomes from previous litters and use that information in future breeding decisions.
Practical Guidance for Puppy Owners
An owner should:
Continue exposure without overwhelming the puppy.
Introduce novelty at a manageable distance and intensity.
Reward curiosity and calm investigation.
Avoid forcing the puppy toward something he genuinely fears.
Provide structure and fair boundaries.
Prevent uncontrolled dogs or people from frightening the puppy.
Build body confidence through safe movement and varied terrain.
Choose training appropriate for the individual dog.
Watch recovery, not only the first reaction.
Seek qualified veterinary or behavioral help when fear, aggression, pain, or sudden behavioral change appears.
The goal is not a puppy who reacts to nothing.
A living animal will notice, startle, hesitate, and sometimes make mistakes.
The goal is a dog who can process the world, recover, learn, and remain connected to the person responsible for guiding him.
The Southernwind Philosophy
For decades, people have asked whether great dogs are born or made.
After a lifetime with German Shepherds, working dogs, horses, breeding programs, training fields, and thousands of puppies, my answer has never changed.
They are born with possibilities.
They become exceptional through purposeful breeding, thoughtful development, responsible training, suitable placement, and the countless daily experiences that shape who they become.
Genetics establishes the foundation.
Environment cannot replace that foundation, but it can strengthen it, neglect it, misuse it, or allow it to reach farther than anyone expected.
That is why breeding and development must never be separated.
The breeder creates possibilities through selection.
The mother begins shaping those possibilities.
The early environment opens the puppy’s world.
The owner continues the work throughout life.
Genetics writes the first chapter. Environment determines how much of that story is ever told.
Frequently Asked Questions
Are dogs’ personalities determined by genetics?
Genetics influence behavioral tendencies, including aspects of fearfulness, sociability, motivation, reactivity, and trainability. However, personality is not determined by genetics alone. Development, learning, health, relationships, and life experiences all contribute to the individual dog.
Can socialization overcome poor genetics?
Socialization may improve coping ability, familiarity, confidence, and behavior, but it cannot reliably eliminate every inherited vulnerability. Socialization develops existing potential; it does not manufacture a completely different genetic temperament.
Can poor socialization ruin a genetically stable puppy?
A stable puppy may tolerate developmental mistakes better than a highly sensitive puppy, but poor experiences, chronic isolation, uncontrolled fear, pain, or inappropriate handling can still damage behavior and prevent the dog from reaching his potential.
When does puppy development begin?
Development begins before birth. Parental selection, maternal health, prenatal conditions, birth, maternal care, early handling, nutrition, and environmental experiences all form part of development.
What is the most important puppy socialization period?
Early puppyhood contains a sensitive period during which social and environmental experiences can have lasting effects.
The precise timing varies among puppies and studies, so development should not be reduced to one rigid deadline. Appropriate learning and exposure must continue throughout life.
Should puppies be exposed to loud noises to make them fearless?
No puppy should be overwhelmed by intense noise in the name of confidence building. Sound exposure should be controlled, gradual, and adjusted to the puppy’s response. The objective is calm recovery and learning—not forcing the puppy to endure fear.
Can temperament testing predict an adult dog perfectly?
No. Puppy testing provides observations from one developmental moment under particular conditions. It may help identify tendencies, but it cannot perfectly predict adult behavior. The dog’s genetics, development, health, training, home, and future experiences remain important.
Why do puppies from the same litter behave differently?
Littermates share parents but do not inherit identical combinations of genes. They may also experience differences in uterine conditions, birth, maternal interaction, health, learning, and human relationships. Each puppy is an individual.
About the Author
Maria Cecilia Martinez is the founder of Southernwind Kennels LLC and has worked with German Shepherds and Belgian Malinois since 1974. Her experience spans more than five decades of breeding, puppy development, training, temperament evaluation, canine education, and working-dog selection.
She is a former AKC and FCI judge and FCI temperament-test judge. Her professional history also includes approximately twenty-two years working with and advising the Puerto Rico Mounted Police, alongside a lifetime devoted to the breeding, development, and training of dogs and horses.
Through The Southernwind Canine Knowledge Library™, she combines firsthand experience with established canine science to help breeders and owners understand the dog as a complete animal: genetics, body, temperament, development, environment, and relationship.
Recommended References
Pfaffenberger, C. J. The New Knowledge of Dog Behavior. Howell Book House, 1963.
Pfaffenberger, C. J., Scott, J. P., Fuller, J. L., Ginsburg, B. E., and Bielfelt, S. W. Guide Dogs for the Blind: Their Selection, Development, and Training. Elsevier, 1976.
Scott, J. P., and Fuller, J. L. Genetics and the Social Behavior of the Dog. University of Chicago Press, 1965.
Morrill, K., et al. “Ancestry-Inclusive Dog Genomics Challenges Popular Breed Stereotypes.” Science, 2022. Original study
MacLean, E. L., et al. “Highly Heritable and Functionally Relevant Breed Differences in Dog Behaviour.” Proceedings of the Royal Society B, 2019. Original study
Foyer, P., et al. “Levels of Maternal Care in Dogs Affect Adult Offspring Temperament.” Scientific Reports, 2016. PubMed record
Bray, E. E., et al. “Effects of Maternal Investment, Temperament, and Cognition on Guide Dog Success.” Proceedings of the National Academy of Sciences, 2017. PubMed record
Nagasawa, M., et al. “Basal Cortisol Concentrations Related to Maternal Behavior During Puppy Development Predict Post-Growth Resilience in Dogs.” Hormones and Behavior, 2021. PubMed record
Bray, E. E., Otto, C. M., Udell, M. A. R., Hall, N. J., Johnston, A. M., and MacLean, E. L. “Enhancing the Selection and Performance of Working Dogs.” Frontiers in Veterinary Science, 2021. Scientific review
McEvoy, V., et al. “Canine Socialisation: A Narrative Systematic Review.” Animals, 2022. PubMed record
Stolzlechner, L., et al. “Optimising Puppy Socialisation: Short- and Long-Term Effects of a Training Programme During the Early Socialisation Period.” Animals, 2022. PubMed record
Hunt, R. L., et al. “Effects of Environmental Enrichment on Dog Behaviour: A Review.” Animals, 2022. Full-text review
Gaillard, V., et al. “Environmental Risk Factors in Puppies and Kittens for Developing Chronic Disorders in Adulthood.” Frontiers in Veterinary Science, 2022. Scientific review
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