Popular Beliefs About Dogs That Science Has Largely Disproven

This formula likely originated as a simple public health reminder that dogs age faster than humans, but it was never derived from biological data. A study published in Cell Systems in 2020 used epigenetic analysis — specifically DNA methylation patterns — to map canine aging and found that dogs age very rapidly in early life and then slow down considerably. A one-year-old dog is biologically closer to a middle-aged human than a seven-year-old child. Large breeds also tend to age faster and have shorter lifespans than small breeds, a distinction the simple formula ignores entirely.

The dominance theory popular in dog training during the mid-20th century was built largely on observations of captive, unrelated wolves — a situation that doesn't reflect how wolves or dogs naturally organize themselves. Researchers, including those who originally studied wolf hierarchies, have since clarified that wolf packs in the wild function more like family units than rigid rank structures. Dogs are not perpetually scheming to outrank their owners; behaviors like jumping, counter-surfing, or pulling on leash reflect unmet needs, incomplete training, or reinforcement history — not a power grab. Reward-based training addresses these behaviors more effectively and without the relationship damage that punitive methods can cause.

Research into canine body language has shown that the direction and speed of a wag carry different emotional signals. A loose, wide wag that involves the whole body is generally a positive signal. A stiff, slow wag held high, or rapid wagging paired with a tense body, can indicate alertness or stress. A 2007 study published in Current Biology found that dogs tend to wag more to the right when approaching something positive and more to the left in response to something threatening. Reading a tail wag in isolation — without considering the dog's overall posture, ear position, and context — can lead to misread situations and unexpected bites.

A widely cited study by animal behaviorist Alexandra Horowitz found that dogs displayed the so-called guilty look — crouching, avoiding eye contact, flattening ears — based on how their owner behaved, not on whether the dog had actually done anything wrong. Dogs who were wrongly accused by owners still showed the guilty expression. What owners interpret as guilt is more accurately described as a stress or appeasement response to perceived human displeasure. Dogs live in the present moment and do not retrospectively connect a past action with current punishment the way humans might assume.

This saying reflects a bias, not a biological reality. While puppies have developmental windows during which socialization is especially impactful, adult dogs continue to form new associations and learn new cues throughout their lives. Senior dogs may process information more slowly and benefit from shorter, more frequent training sessions, but cognitive decline severe enough to prevent learning is a medical issue — not an inevitable consequence of age. In fact, mental stimulation through training is considered beneficial for aging dogs and may help maintain cognitive function. Always consult a veterinarian if you notice sudden changes in a senior dog's behavior or responsiveness, as these can signal underlying health issues.

This belief likely persists because dogs licking wounds appears to provide some soothing effect — and while saliva does contain certain compounds with mild antimicrobial properties, a dog's mouth is also home to a wide array of bacteria. Some of these, such as Pasteurella, Capnocytophaga, and Staphylococcus, can cause infections in humans, particularly in people with compromised immune systems. The comparison to human mouths is essentially meaningless — both species carry bacteria suited to their own biology. For more on keeping your dog's oral health in good shape, see our article on dog dental care.