Though not fully understood, there are various theories as to why dogs tilt their heads:
To hear better:
Dogs will tilt their heads to reposition their ears to better judge the sound’s location and distance. Physiologically, the turning of their head helps open up their ear canal. This also helps with trying to identify familiar sounds and audio cues.
To get a better view of our facial expressions:
Some experts believe that tilting the head helps dogs get a better view of our facial expressions. Stanley Coren, author of the book The Intelligence of Dogs, suggests that dogs with longer muzzles have an obstruction of view comparable to holding a fist up to our nose. By tilting their heads, they get a better view of our facial expressions.
To help pinpoint what they are hearing:
Dogs rely heavily on audio and visual cues. They can detect the slightest change in the tone of our voices and will try to decipher familiar sounds that might interest them. By cocking their head, they can concentrate on identifying important audio cues that lead to positive enrichment for the dog, like getting a treat or going on a walk.
We’ve trained them:
Because we are so fond of this behavior, we commonly use positive reinforcement like praise or treats that inadvertently train our dogs to exhibit head tilting for rewards.
Head tilting has also been documented in various Canid species including wolves, coyotes, and more closely in foxes where they use their excellent hearing and head tilting to find rodents hidden deep within the snow.