"By using large a sample of dogs than any used previously to examine behavior in dogs, we found significant correlations between neutering dogs and increases in aggression, fear and anxiety, and excitability, regardless of the age at which the dog was neutered. There were also significant correlations between neutering and decreases in trainability and responsiveness to cues. The other three behavioral categories examined (miscellaneous behavior problems, attachment and attention-seeking behavior, and separation-related behavior) showed some association with neutering, but these differed more substantially depending on the age at which the dog was neutered. The overall trend seen in all these behavioral data was that the earlier the dog was neutered, the more negative the effect on the behavior. A difference in bone length was found between neutered and intact dogs, suggesting that neutering has an effect on bone growth, which may be related to other orthopedic effects documented in the literature. " I found this information in several different veterinary journals, VERY interesting! I noticed that, working at the pet hotel and meeting thousands of dogs, I almost never saw a DA intact dog of either gender. I would say 99% of aggressive dogs were altered. Now, that could be the result of owners trying to remedy behavioral issues by altering their dogs. However I would think that at least a few of the intact dogs that came in would be aggressive. I can only recall one. The rest were great with other dogs and tended to be much more playful. Intact males couldn't play with "group" dogs, who were approved breeds & altered. So we had lots of intact male play groups, and never encountered a fight between them! Yes, by like leggy, I mean disproportionate. I wish I still worked at the pet hotel, I could get some awesome picture examples! Lots of Labs who were obviously altered very young.