Dogs need to stop and smell the roses, too! A new study finds that the more time dogs get to exercise their noses, the happier they are.

There are all kinds of ways that dog owners try to keep their pets happy. But while a new stuffed animal toy can certainly help—what could be more fun than tearing something cute into a thousand tiny shreds?—new research shows that there’s one beneficial activity dog owners may be overlooking: Sniffing.

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A dog’s sense of smell is estimated to be somewhere north of 10,000 times more powerful than ours. Smells are how dogs interpret the world, as much as vision is to humans. But a new study from dog behavior experts Charlotte Duranton and Alexandra Horowitz makes the point that dogs, despite their free spirits, are not exactly free to do whatever they want, whenever they want. They are, argue the researchers, “captive animals,” in a sense, and can’t always exercise their instincts. Depending on the breed, dogs might want to hunt, herd, run, fetch, dig, or track, instincts that mostly lay fallow while the dog hangs out at home. Owners make an effort to let dogs act on those instincts, but it isn’t always possible.

The researchers wanted to see whether exercising one fundamental instinct—investigative sniffing, or “olfactory foraging”—could have an impact on a dog’s mood. The way they gauged the dog-tester’s moods is pretty clever. They set out two bowls, some distance apart, and trained the dogs to understand that one bowl always had food in it, and that the other one never did. Then they put out a new bowl equidistant from those two bowls, and measured the amount of time it took the dog to approach it. The researchers reasoned that a quicker approach means optimism (the dog thinks there could be food in the bowl).

This study took a two-week break but tasked the dogs with homework. Some were given basic obedience training (which dogs actually like; they want to work), and the other dogs were given “nosework” training. Nosework is an increasingly popular form of training that has dogs using their sense of smell to find and recognize specific scents (birch, anise, and clove are popular) and then complete tasks based on finding those scents.

The control group had no change in those optimism tests after the two-week break, but the dogs that had done nosework as homework approached the mystery food bowl much faster than they did before—indicating that they’re happier, according to the researchers.