Why does my dog watch TV?

It seems that dogs view TV differently than us humans. First, their vision is dichromatic (primarily see in blues& yellows), see less of color spectrum than humans, and they process visual changes faster than us. They can identify if another dog is on the screen and may respond to things aligned with his personality & breed (for example, a terrier may react to squeaky squirrel type noises). That auditory stimulation might be capturing attention as much as the visual and is likely what captures the dog's attention in the beginning and then they look further at imagery in determining where noise came from.