I am currently reading The Culture Clash by Jean Donaldson, which is a fab read and I highly recommend it (although she doesn't like us people who use 'strangle collars' and doesn't really endorse pack behaviour or dominance theories) but it has a lot of sense re behaviours (chewing is natural dog behaviour, they don't do it to annoy us, disbelieving that dogs don't reason or moralise like us, being upset at the thought that they don't actually 'understand every word we say' is like expecting us to be able to sniff out drugs and explosives) and she has a table of what we see and what dogs see, like:
Speaker system = food
Carpet = toilet
Speaker system = toilet
Toilet tissue = food
Post van = rapidly disappearing fast-moving projectile
Cat = rapidly disappearing fast-moving projectile