Dogs live in the world of scent
Sight is our primary sense, and we learn most about our world with out eyes. In dogs, however, the sense of smell is far more important, and much of the information they gather from their environment goes in through their nose. Watch a dog and owner as they enter a new room. The human will use his eyes to find out what goes on there, whereas the dog will go sniffing around to discover what he needs to know.
Dogs can detect odors in a way that we find hard to contemplate. They can easily follow the route taken by a person who passed through a room hours, sometimes days, earlier, leaving no visible signs, or they can sniff out minute amounts of drugs or explosives through layers of packaging and containers.
A dog's sense of smell is known to be at least 100 times keener than our own and may be even greater. The area inside the dog,s nose that detects scent is about 14 times larger than ours, and the part of its brain that processes the information is proportionately larger and better developed . Consequently, dogs are not only better able to detect smells than we are, but they are more interested in them too.
In the wild, the sense of smell would have been of great value to dogs, not only for the detection of prey, but for the maintenance of social groups and the defense of territory. Being able to tell who your friends and enemies are, when they all look similar, is very useful. Knowing the sex state of health, age, and reproductive state from one sniff can answer a lot of question!
This amazing ability has been handed down to out own pet dogs, and it helps to explain why they are so fascinated by scents, and why they go to great lengths to gather information through their nose. By sniffing every lamp-post or putting their noses into all the wrong places when investigating new people, dogs are gathering information about their environment that may be useful to them later, in much the same way as you or I will obtain clues about our environment by using out eyes.