Researchers from the University of Porto in Portugal led a study on dog-training methods and responses. They recruited 42 dogs from training schools that use reward-based training and 50 dogs from aversion training, and the results were amazing.
The study found that yelling at a dog actually scares them long-term, and showing them patience is a far better training method.
Dogs that were taught with leash-jerking, yelling, and other aversive-based methods were more stressed overall. They had higher levels of cortisol in their saliva, displayed stress-related behaviors and body postures, while their counter-parts with calm and gentle teachers were better at performing tasks.
The dogs with the aversive training were slower and less enthused at performing the same tasks. Researchers analyzed the dogs for "stress behaviors,"' too, such as lip-licking, paw-raising, yawning, and yelping. Overall, the study found that the welfare of dogs trained with negative reinforcement was deemed "at risk."