Critical Periods Of Development In Dogs: What Every Dog Owner Should Know

By Norma Jeanne Laurette ​

Introduction

​A dog’s behavior, social skills and emotional resilience are not predetermined, instead they are shaped by experiences during early development. Its behavioral development follows a series of stages, each defined by critical periods where the brain is most vulnerable to learning and environmental influences. These are short yet powerful windows of opportunity when what happens or does not happen has lasting effects on the dog’s personality, temperament, trainability and resilience as an adult dog R1.

Understanding these critical periods is essential for breeders, trainers, veterinarians and guardians alike. Positive socialization, training and imprinting during these stages not only prevents many common behavior problems, they also ensure a great temperament, happy dog and quality of life. On the other hand, neglect, trauma and lack of proper guidance during these windows can result in fear, anxiety, aggression and a myriad of behavior problems that can become difficult and time consuming to change R2.

Gestation Period Of Development (Conception To Birth)

​Many people are unaware of the importance of a healthy and happy mother to the future wellbeing of her unborn pups. Mothers that experience an unusual amount of stress or anxiety during pregnancy are likely to give birth to puppies that are innately sensitive, anxious and often reactive. If the mother is emotionally stable and in good health while carrying her puppies, chances are the pups will be as well. After a puppy is born, it’s experience that shapes its behaviour and personality.

Neonatal Period Of Development (0 to 2 Weeks)

​The neonatal period of development starts at birth and lasts until the eyes and ears begin to open. During this time, the puppies are deaf and blind, they’re entirely dependent on their mother and they spend all their time nursing and sleeping. Although short, this stage still offers an opportunity to begin shaping behavior and stress resilience through calm, gentle and careful handling. Short, controlled handling sessions have been shown to improve cardiovascular health, strengthen the immune system and produce puppies that are more tolerant of stress later in life R3. While no behavioral training occurs during this stage, it is the foundation upon which trust and tolerance begins. For more information about how to prevent and treat stress in dogs see my article entitled Stress & Anxiety – Protecting Your Dog’s Health & Happiness.

Transitional Period Of Development (2 to 3 Weeks)

​During the transitional period, the puppies begin to open their eyes and ears. They become more active, start to interact with their littermates and begin to explore their immediate surroundings. This is a short yet important stage of sensory awakening. Human contact during this stage should increase gradually and carefully. Gentle handling, exposure to subtle scents and new surfaces as well as positive interactions with people help the puppies to associate human presence with safety and comfort. On the other hand, early unpleasant experiences such as rough handling, startling events or anything more than very short separations from the mother and litter can begin to shape fear responses even at this early age R4.

Socialization Period Of Development (3 to 14 Weeks)

The socialization period of development is the most influential and most important stage in any dog’s life. It includes two important sub-categories, which are socialization with other dogs (starting with littermates and mother) and socialization with people and the environment.

Dog/Dog

​From three to seven weeks of age, puppies develop essential social skills through play with their mother and littermates – including bite inhibition, reading and using body language as well as learning to distinguish friendly interactions from conflict. Unless in the hands of a qualified puppy raiser with access to suitable dogs, puppies removed from their litter before 8 weeks can fail to develop proper dog/dog social skills, which could lead to issues down the road such as poor bite inhibition, fear, reactivity and dog-dog aggression R5. For more information about socialization see my article Socialization – Why It’s More Important Than Dog Training.

Dog/Human & Environment

​Between 8 and 14 weeks of age, puppies are at a critical stage for bonding with people and adjusting to new environments. During this time, their brains are highly adaptable and they quickly adjust to new experiences. Pleasant exposure to a wide range of stimuli including a variety of people, animals, surfaces, sounds, vehicles, grooming tools, new environments, etc. nurtures a resilient, confident adult dog R6. However, unpleasant experiences or a lack of exposure during this period can result in deeply rooted fear and reactivity. For example, a puppy that never sees children during this stage can develop a life long fear of children. This is why both the Canadian and American Veterinary Associations urge guardians to begin socialization as early as possible. Carefully managed puppy classes, visits from safe guests, car rides and exploration of various environments are all essential activities during this time R7.

Fear Imprint Periods Of Development (8 to 11 Weeks & 6 to 14 Months)

Within the socialization period are two separate fear imprint periods for dogs, the first is between 8 and 11 weeks of age and the second between 6 and 14 months of age.

First Fear Imprint Period

During the first fear imprint period puppies become cautious and are more likely to form unpleasant associations with frightening experiences such as loud noises, punishment or aggressive encounters with people or other dogs, which can result in fear memories for the rest of the dog’s life R8.

Second Fear Imprint Period

The second fear imprint period occurs during adolescence, which is anywhere from 6 to 14 months of age depending on the size of dog. It typically coincides with a surge of hormones and increasing independence. Dogs can suddenly become fearful of things they previously tolerated and behaviors such as leash reactivity or anxiety can seem to come out of nowhere.

Both fear imprint periods are normal yet require special handling and attention. Harsh corrections or forcing the dog into frightening situations can cause regression and create long-term behavioral issues. Positive training, patience, consistency and reassurance are crucial during these stages R9.

Juvenile Period Of Development (3 to 6 Months)

The juvenile stage in dogs is similar to the toddler phase in children. Puppies are playful, energetic and increasingly curious. They begin to test boundaries and can become selective listeners. As a puppy’s confidence increases, it’s not uncommon for unwanted behaviors to return such as chewing, jumping up or nipping. Rest assured this is a normal part of development and a perfect time to polish basic training cues and continue socialization. With consistency, clear communication and ongoing pleasant experiences, the puppy will come through this stage a well-mannered and well-trained dog. Puppies that receive regular, positive training during this time are likely to grow into dogs that are easier to manage, more attentive and emotionally balanced R10. For more information about positive training see my article entitled Positive Dog Training – Science | Ethics | Results.

Adolescence (6 to 18 Months)

Adolescence can be the most challenging period of a dog’s development. As hormones change, so can behaviors. Dogs that were previously well-trained can become more easily distracted and test boundaries, and they can show signs of increased fear or aggression. Their impulse control weakens as their physical energy peaks. Many dogs are surrendered to shelters during adolescence due to behavior problems that stem from unmet needs, lack of training and/or socialization as well as unfair and unreasonable expectations R11. Guardians who persevere through this stage with continued training, exercise, socialization, canine enrichment, behavior management and consistency will see a big improvement as the dog reaches full maturity. Positive training continues to be the most important, effective and humane way to shape the dog’s behavior during this unpredictable period. For more information about canine enrichment see my article Canine Enrichment For Dogs.

Adulthood (18 Months & Up)

​When A Dog Reaches Sexual, Mental, Emotional & Social Maturity

As dogs reach full maturity their personalities stabilize and if they’ve had positive experiences, they are more capable of handling stress, new stimuli and social interactions with grace. However, socialization should never end at maturity.
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Ongoing exposure to new people, suitable dogs, places and experiences helps prevent regression and keeps the dog emotionally adaptable and resilient. Dogs can learn new things at any age, however adolescents and adults are less flexible and resilient than puppies. If the dog has had traumatic experiences or lacked proper training and/or socialization early in life, behavioral rehabilitation may be necessary. While it’s always possible to improve a dog’s behavior through rehab, the earlier it receives positive social and environmental exposure, the easier it will be to prevent long-term behavior problems R12.

Summary

Early experiences during a puppy’s critical periods of developmental play an important role in shaping their personality for life. Every touch, sight, sound and interaction during these key stages contributes to the adult dog’s ability to function in a challenging world. The window for shaping these experiences is very short and the consequences good or bad are for life. By planning ahead and meeting all the dog’s needs during these critical stages, we can nurture a great dog with an amazing and resilient temperament, while ensuring its happiness and quality of life.

References

​R1: Scott, J. P., & Fuller, J. L. (1965). Genetics and the Social Behavior of the Dog. University of Chicago Press.
R2: Serpell, J., & Jagoe, J. A. (1995). Early experience and the development of behavior. In J. Serpell (Ed.), The Domestic Dog: Its Evolution, Behaviour and Interactions with People (pp. 79–102). Cambridge University Press.
R3: Battaglia, C. L. (2009). Periods of early development and the effects of stimulation and social experiences in the canine. Journal of Veterinary Behavior, 4(5), 203–210.
R4: Lindsay, S. R. (2000). Handbook of Applied Dog Behavior and Training, Vol. 1: Adaptation and Learning. Wiley-Blackwell.
R5: Freedman, D. G., King, J. A., & Elliot, O. (1961). Critical periods in the social development of dogs. Science, 133(3457), 1016–1017.
R6: American Veterinary Society of Animal Behavior (AVSAB). (2008). Position Statement on Puppy Socialization. https://avsab.org/
R7: McConnell, P. B. (2002). The Other End of the Leash: Why We Do What We Do Around Dogs. Ballantine Books.
R8: Overall, K. L. (2013). Manual of Clinical Behavioral Medicine for Dogs and Cats. Elsevier.
R9: Miller, P. (2008). The Power of Positive Dog Training. Howell Book House.
R10: Donaldson, J. (2005). Culture Clash: A Revolutionary New Way to Understanding the Relationship Between Humans and Domestic Dogs. Dogwise Publishing.
R11: Patronek, G. J., Glickman, L. T., & Moyer, M. R. (1995). Population dynamics and the risk of euthanasia for dogs in an animal shelter. Journal of the American Veterinary Medical Association, 206(7), 1001–1004.
R12: Shepherd, K. (2009). Behavioural Medicine for Small Animals. Elsevier Health Sciences.
R13: Dogs Trust. Dog Behavioural Development. Notes that “some small/miniature breeds may be sexually mature at 6–7 months, while some larger breeds may not reach this stage until they are 18–24 months.” dogstrust.org.uk
R14: AKC Staff. Sexual Maturity in Puppies: What Puppy Owners Should Know & Expect. Covers how sexual maturity varies based on breed size, and mentions that “certain giant breeds may not reach sexual maturity until they are older.” American Kennel Club
R15: Hill’s Pet Nutrition. When Does My Puppy Become an Adult Dog? Describes that while many dogs become sexually mature around 6 months, “large breeds may … keep growing until they’re 2 years old,” and emotional maturity often comes by around their second birthday. Hill’s Pet Nutrition
R16: Purina. Puppy Development by Week. Gives a size-based maturity chart: e.g., “large breeds … typically reach adult maturity … at 18–24 months” and “giant breeds … > 24 months.” Purina
R17: Eukanuba. Puppy Development Stages and Behavior into Adulthood. Notes that “a puppy’s emotional maturity often develops quicker in small breeds than in larger ones,” and highlights behavioral markers around 12–18 months. Eukanuba
R18: Frontiers in Veterinary Science. Age Groups in the Dog. This more scientific article discusses neurological reorganization during adolescence in dogs. It states puberty is considered at ~6–9 months for males and up to 16 months for females, and “behavioral and social maturity may be reached between 12 and 24 months … depending on the breed.” Frontiers
R19: Clinician’s Brief / Developmental Stages of Puppies. Notes that “sexual behavior is generally observed at ≈ 6 months … although it may be delayed in large and giant breeds.” It also says “Large-breed dogs may not mature socially until they are 18 months of age or older.” CTF Assets
R20: GSD Council Australia. Veterinary Information Sheet on Growth and Feeding Puppies. States that “giant breeds … can take … 18–36 months to mature.” gsdcouncilaustralia.org
R21: AAHA (American Animal Hospital Association). Canine Life Stage Guidelines (2019). Their chart shows “social maturity” ending around 3–4 years for some breed sizes. AAHA

Photo By Norma Jeanne Laurette