Puppies are hard-wired to appeal to us, with their adorable squishy faces, little paws, and wet noses. But there is more to young dogs than downy fur and floppy ears. Here are 12 scientific facts about them to coo over on Puppy Day:
1. THEY LIKE BABY TALK.
A January 2017 study found that puppies respond when humans speak in sing-song tones, but adult dogs couldn’t care less. Researchers from the University of Lyon at Saint-Etienne found that people speak more slowly and at a much higher pitch when talking to puppies (or pictures of them, at least) than when talking to humans or adult dogs. When the researchers played recordings of participants’ puppy talk to dogs, they found that the puppies showed greater responses to the cooing than to recordings of humans using their regular (human-directed) voices. Adult dogs, on the other hand, did not. It’s hard to say why that is, but it could be that puppies are wired to respond to high-pitched sounds, but they eventually grow out of it.
2. THEY CAN HELP YOU FOCUS.
Looking at cute pictures of puppies at work is more productive than you’d think. In a 2012 study, Japanese researchers found that viewing pictures of puppies made people better at tasks that required close attention. Viewing pictures of older dogs, however, was not as effective. People were more effective and more careful in accomplishing the tasks before them if they were flooded by the positive emotions of seeing an amazingly adorable baby animal. The researchers suggest that maybe people should look at cute things before driving or at work to help them focus.
3. THEY REALLY DO LIKE YOU.
In a Hungarian study published in 2005, researchers found that pet puppies show specific attachments to the humans that care for them. While even wolves that had been hand-raised from birth by humans didn’t show any preference for the people that raised them—they reacted the same way to strangers as to the caregivers they had spent their entire lives with—domestic puppies as young as 4 months old showed a significant preference to their owners. They followed and greeted their owners more than they did strange humans, and when their owner left, they tended to stand by the door waiting for them to return. This difference was observed in both puppies that had been hand-raised with extensive socialization and puppies that had been reared in a litter by their mothers, indicating that as a species, dogs have evolved to bond with their human owners.
4. THEIR SENSES DON’T DEVELOP UNTIL A FEW WEEKS AFTER BIRTH.
When they’re first born, puppies only respond to warmth, touch, and smell. Their eyes remain closed, and they can’t hear. Puppies don’t fully develop the ability to hear until they are 4 weeks old, and it is not until 6 weeks of age, on average, that they develop full vision. Once their senses develop, they begin exploring the world in earnest, beginning a critical period of socialization.
5. IT’S IMPORTANT TO FAMILIARIZE THEM WITH PEOPLE EARLY.
Studies [PDF] have shown that puppies are most socially malleable during their second month of life. During that time, their sensory systems are developed enough to let them explore, but they’re not yet fearful of new experiences. As one 1961 study on puppy litters isolated from humans found, puppies that aren’t played with showed “increasing tendency to withdraw from human beings after 5 weeks of age and unless socialization occurred before 14 weeks of age, withdrawal reactions from humans became so intense that normal relationships could not thereafter be established.”
6. THEIR PHYSICAL AND EMOTIONAL DEVELOPMENT VARIES BY BREED.
Puppies don’t all develop on the same timeline. A 2015 study of almost 100 purebred dogs found that different breeds of dogs develop a sense of fear at different times in puppyhood. The researchers put puppies from 4 weeks old to 10 weeks old through several tests designed to provoke a fear response, like making them listen to a loud bang or explore a seesaw. They found that Cavalier King Charles spaniels didn’t show fear-related behavior (like crouching down) until later than German shepherds or Yorkshire terriers. While German shepherds typically began showing a fear response around 35 days old, the spaniels didn’t start avoiding scary stimuli until 55 days old.
7. THEY LEARN TO UNDERSTAND HUMAN GESTURES AS THEY AGE.
Dogs can understand human social cues like pointing, but it’s something that they learn over time. In 2007, researchers tested 6-, 8-, 16-, and 24-week-old puppies [PDF] on their ability to decode a human’s finger point. Though these researchers reported that dogs of all ages could understand the cue and use it to find food under a cup, subsequent analysis by another research group showed that actually, those skills improved over time [PDF]. The older the dogs were, the better they were able to understand the pointing and suss out the correct cup. In itself, the act of testing seemed to help them learn, too. The youngest puppies showed improvement between the first half of their trials and the second half, the 2008 follow-up analysis found.
8. THEY DON’T CRY AS MUCH AS ADULT DOGS.
Dogs aren’t born with very moist eyes. One 2012 study found that 4-week-old puppies do produce basal tears, but in much smaller quantities than adult dogs. Their eyes get wetter every day, finally reaching adult levels of tears at about 10 weeks old. By contrast, full-term human babies have eyes which are just as wet as those of adults, unless they’re born premature, in which case they have lower secretions of tears until a few weeks later. (These are just the tears that keep eyes moist, not the psychological kind.)
9. THEIR LITTER SIZE DEPENDS A LOT ON BREED.
How many puppies a dog has varies by breed. While a 2011 review of birth data from 224 dog breeds found that the average purebred dog litter consisted of five or so puppies (5.4, to be exact), older and smaller dogs tend to have fewer puppies. Rhodesian Ridgebacks gave birth to the most puppies (an average of 8.9 puppies per litter), while toy Poodles and Pomeranians gave birth to an average of 2.4 puppies at a time.
10. THEY’RE NOT ALWAYS PLANNED.
In one of the first benchmark studies on pet population trends in the U.S., researchers found that 43 percent of puppy litters in 1996 were unplanned—about 2.6 million compared to 3.38 million planned litters. That’s a lot less than the whopping 83 percent of kitten litters that were unplanned.
11. THEY CAN BE IDENTICAL TWINS.
In 2016, a veterinarian encountered what is thought to be the first verified instance of identical twin puppies. When South African vet Kurt de Cramer performed a C-section on a pregnant Irish wolfhound, he discovered that two male puppies shared the same placenta. Later, he had their DNA tested and confirmed that they were, in fact, identical twins.
12. THEIR BEHAVIORAL TRAITS AREN’T SET YET AT 8 WEEKS OLD.
A long-term study of 1235 German shepherd puppies bred at the Swedish Dog Training Center in the late 1970s and early 1980s found that at 8 weeks old, a dog’s personality is not yet developed enough to analyze. The researchers wanted to know if suitability tests for guide dogs and other working dogs could be accurately performed on puppies as young as 8 weeks old. They found that at that point, puppy behavior is still changing rapidly, and test results from that young wouldn’t reveal much about the future behavior of the dog as an adult. In other words, it’s O.K. if your puppy is an idiot (or rambunctious, or whiny)—he’ll grow out of it, hopefully.