Older dog - but Puppy in the Head?

[magoo]

Just wondering if there are any advisors out there who would agree with this statement...
I adopted a dog - at @13 months of age - who'd spent 10 months of that time in a cage.
He's physically now @20 months
Some people have said I'm dealing with a 3-6 month old in an almost 2 year old body...
Accurate?
Just wondering because I've been doing a LOT of reading on dog behaviour and wonder if I shouldn't think of him as a puppy - and expect less...
J and M

[Maisy Moon]

I had a boxer that remained a pup in his head till he way 9. 3 years as an 'adult' dog and then he passed.....My uneducated theory is that the lower IQ ones tend to remain younger longer but have more fun in their lives.

[Mario Niepel]

Magoo, what do you mean by 'think of him as a puppy - and expect less...'? Puppies from a very young age onward can learn an awful lot of things very quickly, so even if you are correct to assume that somehow your dog will remain a puppy longer (due to his horrible imprisonment), this does not necessarily mean you can or should expect less. Do you have any specific problems or areas where the pup may be lagging your expectations?