If you’ve owned dogs your entire life, do you still believe that one human year is equivalent to seven dog years? You’re not alone. Here’s a list of the top myths about dogs we need to stop believing.

1. One human year equals seven dog years.

This widely popular myth began at a time when people lived to about 70 years old, and dogs about 10. They divided 70 by 10, and that’s how we got the formula, Dr. Ann Hohenhaus, a veterinarian at Animal Medical Center in New York, told Science Insider.

Some dogs are known to live well over 20 years. The oldest one recorded was 29 years old—or 203 dog years using the 1=7 calculation. The figure is mind-boggling, and most definitely false.

In a report in The Telegraph, a new sophisticated computation gives a closer approximate: Each of the first two years corresponds to 12 human years, while all subsequent years count for four human years. That means the oldest pooch, at 29, has lived a more reasonable 105 years old.

There many factors involved in computing a dog’s age, including breed and size. There are calculators available online, but no matter the source, remember the numbers are approximate. Calculating longevity is not an exact science; some dogs will live longer or shorter than expected.

2. Dogs are color blind.

New research has shown that while dogs can’t see colors as humans do, they can still see colors.

“Dogs are partially color blind—they see things in kinda blue, yellow and gray,” said Hohenhaus. Which means that dogs’ vision may not be in technicolor, but they can see so much more than just shades of gray.

This popular myth is attributed to Will Judy, a dog fancier and former publisher of Dog Week magazine. According to the American Kennel Club, Judy claimed to be the first to declare dogs had poor vision. “It’s likely that all the external world appears to them as varying highlights of black and gray,” Judy wrote in his 1937 manual, “Training the Dog.”

Coats as insulation

3. You should shave fluffy dogs in the summer.

Many dog owners shave their dogs in the summer because they think it will make them feel cool, but that’s not true, Dr. Carly Fox, emergency and critical care veterinarian at Animal Medical Center, told Science Insider.

“Dogs have adapted to all types of weather. They actually shed coats in different weather at different times of the year to be comfortable,” Fox said.

Your dog’s fur coat actually gives it relief from the heat, according to a report by the American Society for the Prevention of Animal Cruelty. The coat acts as insulation—it keeps your pup from getting too cold and from overheating in the summer.

The coats have several layers essential to the dog’s comfort in the heat. Shaving them in the summer will rob them of this natural cooling system. This will make them uncomfortable and prone to overheating, and increase their chance of getting sunburned, or worse, skin cancer.

4. Some dogs are hypoallergenic because of their fur.

“All dogs produce allergens; some produce more than others. Dogs that don’t shed—like poodles and smaller dogs that shed less—are less likely to produce large amounts of allergens that can cause allergies,” Fox said.

When choosing a hypoallergenic dog, Fox said you have to deal with how often they shed, or if they shed at all.

5. Dogs wag their tails when they’re happy.

A lot of times, when dogs wag their tails, it seems that they are thrilled and delighted. Tail-wagging, however, is a dog behavior that can mean different things, and not necessarily happiness, Fox said.

“I think that the wag matters, like with Labradors whose tails swish, swish, swish sideways—they’re pretty much happy all the time,” said Hohenhaus.

If a dog’s tail is quivering, that is not a happy wag. If it quivers and then goes under, that is not a happy wag.

“In addition to looking at the ears and the eyes and the body posture, ask yourself what kind of wag it’s doing, because that’s going to give you an indication of the mood of the beast,” Hohenhaus said.

6. Dogs feel guilt.

The truth is, you want your dog to feel guilty for chewing on your designer shoes or new furniture. We want our pups to feel guilt because we want them to be like us—like humans.

“Dogs will display guilt-like behavior when they do something wrong. Like, they’ll put their ears back, or they’ll hide, but I think in most cases that’s a reaction to you—your tone of voice, your anger at them, your body language—rather than true guilt,” Fox said.

Hohenhaus also noted that dogs have become so effective in integrating themselves into the lives of humans for millennia that they are very good at picking up on social cues.

In moderation

7. Human food is bad for dogs.

Chocolate is obviously bad for dogs, and grapes, raisins and garlic are toxic to them. But human food, in general, is not necessarily bad for dogs.

“You always want to limit the quantity of human food you give to dogs. Human food should be less than 10 percent of their diet. Human food in moderation is not bad for dogs,” Fox said.

A good, balanced meal for dogs is dog food, said Hohenhaus. Do your research before purchasing dog food from the grocery shelves. Learn about the company that produced the food, read reviews, learn dog nutrition, because not all dog food are made equal.

“Should I cook for my dog? That is a bad idea because what we eat is not a balanced diet for a dog. Home-cooked meals run the risk of being deficient in nutrition critical for your dog, like calcium and phosphorous. Unless you’ve had a diet made by a certified veterinarian nutritionist, it is a bad idea,” Hohenhaus said.

8. Dogs can’t digest grains.

Fox calls this a “major, major myth.” “Not only can they digest grains, but recent research shows that they need grains. Dogs on a grain-free diet are at risk of developing a serious heart disease called dilated cardiomyopathy (DCM),” Fox said.

9. You can’t teach old dogs new tricks.

Senior dogs will be slower, but you most certainly can teach your old dog new tricks.

That said, training a dog is never easy. It involves a lot of patience, persistence, repetition and rewards. Dogs will get distracted easily, so pick a time when there’s less commotion or activity in the household. You will need your dog’s full attention.

Fox said a study showed teaching the same trick to one set of dogs from six months to one year old, and to another set of dogs more than 10 years old. Both sets, she said, learned the new trick, although the older set took twice as long to learn it.

Some dogs become more stubborn and lazy as they get old.

10. Putting a dog’s nose in its mess will break the habit.

Dogs respond to positive reinforcement. Negative reinforcement is “very bad for a dog,” Fox said, and will breed bad and aggressive behavior.

“Ideally, you should always reward your dog with positive behavior, like treats or playtime or feeding,” Fox said.