It can be more than just a learned behavior. I posted on another thread about my brother and sister in law having to put down their cocker spaniel because of "spaniel rage." It was originally called "springer rage" and there are articles on the internet about it.
Many years ago I volunteered at a dog rescue with a gal who had a springer spaniel who, out of nowhere, attacked her face. The dog almost bit this poor woman's nose off and she was having reconstructive surgery. She was devastated. She was volunteering at the rescue because it had scared her so much that she didn't want to develop a phobia about dogs. A couple of years later I heard that she had adopted a couple of golden retrievers.
Originally the specialists thought it was a just a behavior issue but they now think it might be aggressive behavior caused by a seizure disorder. My niece is married to a vet and my brother's vet both said it was from poor breeding....my bro's cocker had come from a backyard breeder.
If you have any questions, I would recommend that you have your vet evaluate your pup and it's always a good idea to sign them up for dog school as soon as they can go, too.