Is there an answer for why dogs tilt their heads? Well, the Sci Show takes a look. Although there's no firm answer to this, but scientists think it may help dogs not only see, but hear better.
Depending on the dog, they might not be able to see the bottom half of your face. So, they tilt it, as they can read your facial expression, and register whether you are happy, angry, etc.
Watch the above video for a full explanation.