Puppies are babies. They have not learned the rules yet; in fact, a puppy does not learn how to properly interact until about 16 weeks of age. Puppies are teething, and it's instinct for them to test boundaries. If they stay with their litter mates longer they tend to learn bite inhibition naturally….however:
There are a couple different ways you can teach your puppy "bite inhibition" - the most common way is to 'yelp' when the puppy bites too hard, and to immediately stop playing or interacting with it. This is what mom, litter mates, and other dogs do when a puppy gets too rough.
I like to stand up and turn my body away; dogs [and puppies] are social animals so shutting off any interaction makes it very clear to them very quickly what they should NOT do. If you keep playing with them they will not get the hint. You will have to do this quite a bit, repetition is key to them learning.
There are other more 'creative' methods I've heard of being used by people on these forums as well…. maybe they'll mention them here.
Another method is to switch out your hand for a toy. Yelping after being bitten too hard is pretty key, but then switch your hand for something more appropriate to chew on.
Another method would be to let the puppy chew on your hand, but then yelp and immediately stop playing with them if they chomp down.
Puppies need lots of things to chew on while they are going through this stage.
My dog has a very soft mouth (softer than any retriever we've had even!) I used the first method mentioned above [ but he also stayed with litter mates until 9ish weeks] most people swear by that method.
I doubt it is aggression just a normal puppy stage and needs to be taught to stop not punished. When our dog was a puppy he would nip us anywhere when overly excited so we tried not to let him reach that excitement level, he would go in his crate for time out(not out of anger just gently pick him up and put him in without a word) and wait till he calmed down, remember you may have to put him in and out until he works it out. Before he gets to that stage of excitement stop the play, if he is going for your hands replace your hand for a toy in his mouth, if he nips your hand make the ouch sound, all this in combination got us through puppy nipping, also everyone has to follow the method you use or puppy will get confused. Good luck.
Jolanda and Kaiser
Yelping may work with some, with others it will just encourage them. (why do we give our dogs squeaky toys?) Disengage from play, certainly. It's called "negative punishment", removing the thing the dog wants (your attention) when it does something you don't like (biting/nipping). Certainly give him a substitute "legal" item to chew.
Usually if you are consistent, the pup will get the message. If you have trouble disengaging (pup goes after you continuing to nip/bite, ignores legal chew toy), I like to apply the "bear hug", which is just physically containing the little guy until he quits struggling/biting/whatever, then immediately release and praise/treat. If he starts again, repeat. Eventually he will figure out that biting is not allowed.
Puppies "talk" with litter mates with mouth… too rough and the others YELL at them... and stop playing... same with adults with puppies but even more so... so they need to learn "soft" mouth... you need to scream... loud... when they play/bite to hard and immediately stop all interaction with them.. that is what the littermates would do... and the adults too... It is not agression at this age unless that particular pup was really dominate to begin with... in that case EVEN more important that they learn the rules...
But it is not going to happen with one or two corrections... it is over time and you and all the family needs to be consistant with their reaction to over the top type of biting.... It is weeks and weeks of corrections (never negative, but positive reinforcement and re-direction)
NEVER punishment... but re-direction ... remember if you stimulate the puppy ... natural reaction is to become a bit wild.. out of control... you need to control that reaction....
Work on working the mind... teaching stand, sit, wait, leave it... bother their mind
Good advice here from all.
What we found with Lela (our first dog ever) is that play-biting at some stage turned into I-bite-you-to-check-if-you-really-are-the-pack-leader-because-maybe-I-could-take-your-place. Whole different energy and dynamics, calling for different corrections. You'll notice after a couple of months (puppy stage 3 or 4).
If you have an adult dog in the household, it will save you a lot of grief. The adults will usually put manners on the pup. I have yet to hear an adult "yelp", but sure have seen them snarl and pin the little so-and-so down momentarily, and when released the pup is usually a bit chastened and leaves the adult alone for awhile. Some need more convincing than others! Lady used to snarl in Tamu's face while holding her down, and watching her is what started me using the "bear hug" (minus the snarling) to correct this behaviour.