Why do dogs sigh? ?

Why does my dog keep on sighing? He's fine, but he keeps on sleeping also. x_X idk what to do
my dog sighs all the time. it's probably because he/she is not happy about something. are you not playing beside him/her enough? walking them enough? etc? mine gets lots of attention and have lots of energy so we run and play with him a lot. but he loves man around people so much i sometimes have to make him lay down to silent down. so he sighs big time to show his discontent. lol. probably the same thing. just produce sure he's getting enough attention and gets to run around plenty to burn off that energy.
It's bored, lower than exercised, and probably lonely for most of the day. It wants your attention! Walk your dog more, take it out for exercise, play beside it, try giving it some mental exercise by click training it. Go watch some Dog Whisperer too, he deals with bored dogs habitually.
he probably needs to be mate
He may be sighing because bored or sad. You might try taking him somewhere such as the dog park or on a tramp! He might be sad and bored because you're not giving him much attention and might be sleeping more because of this. Hope this helps!
Answers:    He's Bored.

Tips:

-Make sure you hold enough toys(or chewtoys)
-Play with him more
-Spend more time with him
He sounds bored.
Try getting him one of those toys where on earth they have to try to get the treat out of it. That should keep him inhabited for a while...
hes sad
Maybe he needs a little more attention.
He is bored or frustrated at not being able to communicate with you. Get out and play near him more.
why do you sigh??
My dog does that, it's so cute. I think it's only a sign of boredom. Just like we sigh, just cause we're bored or whateverish.
bored
Is it a paroxysm or what? Jack Russell Terrier give a hand?   Does this dog look close to a pure breed?   What cause my dog to die? :(?   How do I hold on to my jack russel surrounded by the backyard? ?