News Animals Why You Shouldn't Yell at Your Dog By Mary Jo DiLonardo Mary Jo DiLonardo LinkedIn Twitter Senior Writer University of Cincinnati Mary Jo DiLonardo has worked in print, online, and broadcast journalism for 25 years and covers nature, health, science, and animals. Learn about our editorial process Updated November 11, 2019 12:38PM EST This story is part of Treehugger's news archive. Learn more about our news archiving process or read our latest news. Share Twitter Pinterest Email Yelling at a dog can cause long-term stress. Inna Astakhova/Shutterstock News Environment Business & Policy Science Animals Home & Design Current Events Treehugger Voices News Archive You love your dog, but he probably drives you bonkers at times. Maybe he's developed a taste for socks or won't stop jumping up on your friends. The methods you use to train him can make a big impact on his stress and long-term well-being, a new study finds. My dog Brodie is reactive, meaning when he sees another dog, he barks like mad and spins in circles. Brodie just wants to play, but it sounds like he's a demon from hell. I interviewed several trainers and some immediately wanted to put a prong collar or shock collar on him to keep him in line. Instead I've worked with positive reinforcement trainers who have taught me to use treats, praise and other tools to work on Brodie's issues. He's still a work in progress and there are definitely times when I'm screaming inside my head, but I don't take it out on my dog. And that certainly will make him happier in the long run, according to science. Researchers at Universidade do Porto in Portugal studied 42 dogs from reward-based training schools that used treats or play and 50 from schools that used aversive methods like yelling and jerking on the leash. The dogs were recorded for the first 15 minutes of three training sessions, and saliva samples were taken after training sessions and at home on days when they didn't have classes. Researchers were determining the levels of the stress hormone cortisol in each dog at rest and after training. Researchers also looked for stress behaviors like lip licking and yawning and analyzed the overall behavioral state of the dogs to take note of whether they were tense or relaxed. They found that the dogs enrolled in classes where they were trained with yelling and leash-yanking had higher levels of cortisol in class than when they were at home. They also showed more stress behaviors, especially yawning and lip licking. The dogs that were in positive-reinforcement classes, however, showed fewer stress-related behaviors and had normal cortisol levels in class. "Our results show that companion dogs trained using aversive-based methods experienced poorer welfare as compared to companion dogs trained using reward-based methods, at both the short- and the long-term level," the researchers conclude. "Specifically, dogs attending schools using aversive-based methods displayed more stress-related behaviors and body postures during training, higher elevations in cortisol levels after training, and were more 'pessimistic' in a cognitive bias task than dogs attending schools using reward-based methods." The paper is available on bioRxiv before peer review. Long-lasting impacts of stress Dogs like to learn, so make training sessions a part of each day. Jne Valokuvaus/Shutterstock For the next step, researchers wanted to see if harsh training had a chronic effect on a dog's well-being. The dogs were trained that a bowl on one side of the room always contained a sausage treat. If it was on the other side of the room, it never had a treat. (The bowls were always rubbed with sausage so smell never gave it away.) Then the bowls were placed in other areas around the room to see how fast the dogs would approach them looking for a treat. The dogs that were trained harshly were slower to find the bowl with treats. In these cases, the researchers said the dogs' negative experiences had made them pessimistic dogs. Whereas the dogs that had been trained in a positive manner found the treats more quickly and were more hopeful of being rewarded. Because these dogs seemed to have learned more quickly, this suggests rewards-based training could be more effective than harsher methods. But the researchers point out that this could be because the dogs already understand how the treat payoff works. There's a chance they might learn even more quickly if they were trained with aversive techniques. But training with treats instead of yelling is the way to go if you want your dog to be happy, the researchers say. "Critically, our study points to the fact that the welfare of companion dogs trained with aversive-based methods appears to be at risk."