There was always that ONE dog that lived in your neighborhood when you were a kid. You know, the dog that was more K-19 than K-9, a veritable killing machine designed to destroy the lives of elementary school kids who dared step foot near their owner's property. Or, at least it seemed that way. One thing was for sure, though, that dog was aggressive, and steering clear of him sometimes meant the difference between a leisurely walk home from school and a mad dash for survival. But what is it that made that dog aggressive while so many other dogs are very friendly? According to researchers in Italy, it may be related to something that also makes some humans more aggressive.

Scientists posit that a deficiency in EPA and DHA, both of which are components of omega-3 fatty acids, may cause certain dogs and certain humans to act somewhat aggressively. Research from a number of studies, including those published in the Journal of Clinical Investigation, suggests that EPA and DHA play an important role in behavior and impulse control in humans, something that the recent Italian study found may also be the case for dogs.

While external factors certainly play a role in shaping a person's behavior (as well as a dog's), this research provides an interesting theory for the nature side of the perennial nature vs. nurture argument.