What are whiskers for? New research indicates that rats sense texture with their whiskers, the same way humans use their fingertips.
When you stick your hand in your purse or backpack, and fish around for a specific object, you use your tactile sense. Rats use their whiskers to do the same thing.
Although the study looked only at rats, it's likely that other mammals, including dogs, use their whiskers in a similar fashion.
Read about the study at Science Daily.