Watching a puppy learn is one of life’s most entertaining sights. You practically can see the wheels turning as that clever little brain makes new connections daily. And that’s exactly what’s happening. What you are seeing as a puppy’s genes and environment converge to produce learning and behavior is the wiring of his brain.
Although a puppy is born with essentially all the brain cells he will ever have, his brain grows in two ways: It gets bigger, and it changes shape. How much the brain grows and the way it changes shape depend on the kind of environmental stimulation the pup receives during the first 16 weeks of life, writes Raymond Coppinger, professor of biology at Hampshire College in Amherst, Massachusetts, in Dogs: A Startling New Understanding of Canine Origin, Behavior & Evolution (Scribner, 2001; coauthored with Lorna Coppinger).
Growth comes in the connections between the cells. Dendrites are brain nerve-cell structures that form contacts with other nerve cells. The more connections the dendrites make, the more the brain grows. By 6 weeks of age, a puppy’s brain mass is approximately 70 percent developed, and by 16 weeks of age, almost all the connections have been made. Once brain growth stops, it’s difficult to change the wiring, Coppinger writes.
The critical period for influencing puppies is between 3 weeks and 14 weeks of age, says Lore Haug, D.V.M., a board-certified behaviorist with South Texas Veterinary Behavior Services in Sugar Land, Texas.
“They’re sort of like sponges during that time,” she says. “They don’t have any preconceived notions about environmental stimuli, and they hopefully haven’t been alive long enough to have anything really bad happen to them. There’s a little bit of a neutral response to a lot of things in the environment that allows you to start that socialization , so they can be exposed to a lot of things and end up with a positive experience, a rewarding experience with different stimuli.”
The Wonder Weeks
Before 3 weeks of age, a puppy’s activities consist primarily of eating and sleeping. This is the neonatal, or newborn, period. It might seem as if not much is going on in the brain during this period, but early neurological stimulating exercises, such as holding them, turning them over and exposing them to minor temperature changes, can benefit puppies.
“There’s a window in the life of every puppy that opens on the third day of life and closes on the 16th day,” says Carmen L. Battaglia, Ph.D., who has bred and finished (earned a championship on) a number of dogs, and who is an American Kennel Club judge of more than 40 breeds. “If you stimulate their neurological system during that open window, for the rest of that puppy’s life, he will have a better heartbeat, a better heart rate, more resistance to disease, greater tolerance of stress and a more active adrenal system, so his adrenaline will run faster when he needs it.”
The transitional period begins at 2 weeks of age, when the puppy’s eyes open. During this time, puppies show significant improvement in their ability to learn and can even be trained to perform a response for a food reward as early as 15 days of age, writes veterinary behaviorist Ian Dunbar in Dog Behavior: Why Dogs Do What They Do (Ingram Book Co., 1989).
The transitional period ends when the ears open and the canine teeth emerge, toward the end of the third week. At this point, puppies are suddenly active and busy. They learn that they can sit, and they start trying to walk, although they’re pretty wobbly and still need lots of practice. Puppies during this stage begin playful biting and pawing behavior.
Now the puppies have entered what’s known as the socialization period, the critical time for brain development.
“Three weeks of age is about the time that they’re a little bit mobile, their ears are open, their eyes are open, so they have the ability to taste, smell, obviously touch and hear, so all their senses are functioning,” Haug says. “They can start being exposed to different sounds, visual stimuli, tactile stimuli and things as part of their socialization process.”
It’s also during this period that puppies become more oriented to their environment. They start exploring odors and sounds, and straying away from their mother and the other puppies a little bit more.
Children go through the same kind of phases, Haug says.
Because the socialization period begins at such an early age, a good breeder is essential for success. Puppies must become accustomed to a wide variety of sights, sounds, smells, people and experiences if their brains are to make the neural connections that will allow them to become well-rounded dogs.
A little adversity helps, too. Moderate amounts of stress during the socialization period can prepare a puppy to be ready for anything.
Most often, this is done with puppies being trained for military programs, but any dog can benefit. Stresses can range from changing a pup’s point of view by putting him on a picnic table or washing machine to surprising him with a toy during a game of peek-a-boo.
Battaglia likes to see how puppies react to a change in elevation.
“I put them on the table to see how they handle change and how they handle differences in their environment, all of which for them is unexpected,” he says. “One of the things that happens when you put a puppy on the table is that he’s seeing the world from a different place. Usually, he sees the world from the ground, and when he looks up at you, your shape is different than when you put him on the table and he’s halfway up your side.”
Some puppies don’t seem to be bothered by the change. Others are nervous or fidgety; they can’t wait to get off the table. “When you go to the military programs,” Battaglia says, “look at what they do to early puppies, 4-month-old puppies: noise level, surprises all over the place. Then, look at those same puppies when they’re 8, 9, 10 months old. There’s almost nothing that fazes these guys. They’re alert; there’s an animation about them. That isn’t the way they were when you saw them younger. Put a puppy up on that table, and see how he handles a little adversity in his life. Keep bringing adversity into his life so that after a while you’ll find that these puppies pretty much can handle anything.”
The age at which a puppy goes to his new home can also affect his development. Traditionally, puppies have gone to new homes at 6 to 8 weeks of age, but more and more breeders
— especially breeders of toy breeds, such as Yorkshire Terriers — prefer to keep their pups until they’re at least 10 to 12 weeks old. The additional time with mother and littermates helps them develop more fully, they believe.
Yorkies mature slowly, and reputable breeders won’t let them go before they’re 12 to 14 weeks old, says Yorkshire Terrier breeder Doreen Hubbard of Marysville, Washington. There’s a physical bonus as well, she says. Yorkies go through a trouble-filled teething stage during which they lack appetite and often have diarrhea. “I hate seeing somebody buy a dog who is going to worry them the first month they have him, wondering why he isn’t eating, why he’s got diarrhea,” she says, advising to let the breeder take care of that.
Haug agrees that there are psychological and behavioral lessons a puppy can learn through a longer stay with his mother and littermates.
Those behaviors include bite inhibition
— learning how not to inflict injury with the teeth — as well as other perceptual, motor and social skills. A 6-week-old puppy who’s weaned and rehomed at that age misses those lessons, but whether a longer stay at the breeder’s home is beneficial depends a lot on the quality of the breeder.
“We’ve made observations that puppies who are weaned and sent away early often do have more behavior issues, more difficulty adapting to new homes than puppies who are sent out a little bit later,” Haug says. “The flip side of that is if the breeder’s home lacks effective socialization experiences. For example, if a breeder keeps a puppy until he’s 10 weeks of age, but the puppy lives in the backyard, doesn’t meet visitors or other animals or isn’t handled that much, your socialization window is almost closed by the time you rehome the puppy, so your puppy grows up to have a socialization deficit.”
A puppy from this type of environment won’t have the same amount of brain development as a puppy who grows up in a more enriched setting.
But when a breeder does a good job of socializing the litter, taking the puppies out on walks and to different places and exposing them to different sights, sounds, people and animals in a controlled way, then it probably is better for puppies to stay there longer, Haug says.
It’s important for socialization to continue and even increase after the puppy goes to his new home. Puppies need exposure to many new people, dogs, cats, bicycles, household sounds such as blenders and vacuum cleaners
— anything that they might need to deal with on a regular basis throughout their lives. It might seem as if your Yorkshire Terrier puppy is getting lots of exposure to people, but he might not be meeting enough different people.
“The mistake a lot of people make with socialization is not providing enough novelty,” Haug says. “The puppy will, say, be exposed to other dogs in the home or friends that come over to the house, and he meets those friends frequently, so you’re thinking that the dog’s getting exposed to a lot of people, but he’s not. He’s really only meeting about eight people; he just meets them over and over again.”
Novelty means that a puppy meets brand-new people and animals and has brand-new experiences every week, multiple times a week. This gives the puppy a broad exposure pattern and broad experience to draw on later in life. A puppy who has met only middle-aged people or only friends of the owner is less able to cope when he meets people who aren’t like those he’s used to: children, for example, or people wearing uniforms, people in wheelchairs or people from other cultures.