When you walk your dog, you know they like to sniff. In fact, it's been estimated that dogs sniff around 33% of the time when they're on the move. It’s how they pick up all kinds of information about their environment - including which dogs have been there previously, how big those dogs are, and even what they're feeling. And here’s why it’s good to let your dog have a good sniff. This comes from evolutionary biologist Dr. Mark Bekoff at the University of Colorado:

First, picking up the scent of another dog in the neighborhood is like checking out their Facebook page before they meet in person. And it can help dogs have smoother introductions when they DO meet.

Next, sniffing is mentally stimulating for dogs, the same way reading a good book is for us. And NOT letting them sniff around is a form of sensory deprivation.

And sniffing makes dogs happy and optimistic. In experiments conducted by the Dog Cognition Lab at Barnard College, dogs that were allowed to sniff - versus dogs made to heel exclusively - were more optimistic about finding food rewards. That’s how their optimism was measured.

So make sure when you walk your dog you give them a chance to use their nose.