Science writer Eva Frederick reviews the results of a study on punishment-based dog training performed at the University of Porto, in Portugal. Researchers found that using “aversive” techniques–such as shock collars, yelling, or harshly tugging at a leash to correct bad behavior–does a lot more harm than good. When we repeatedly cause dogs pain or fear in an attempt to make them do what we want, their coritsol levels increase, and they develop a “pessimistic” mindset–which can actually create behavioral problems, such as separation anxiety. Our canine companions learn more from reward-based training, respond to treats, play, and affection, and are easier to teach if they have an “optimistic” attitude. Want a well-behaved dog? Give him or her a bone!