By Martin Cassidy
BBC Northern Ireland rural affairs correspondent
Scientists have got to the bottom of stress in pigs, delving into the background and motivation of animals who seem to make life difficult for themselves and others.
It's a salutary tale where a poor background and naked ambition can lead to a life of aggression and stress.
Pushy pigs are prepared to endure high levels of stress
When she began studying pig behaviour at the Agricultural Research Institute at Hillsborough in County Down, scientist Niamh O'Connell was soon struck by the human parallels in the complex social structures which rule the lives of pigs and people.
Not that it's all hustle, bustle and stress in the pig world.
Niamh says some individuals make a very clear decision to accept lower social status for the sake of a quiet life.
"What is interesting from a human perspective is that low-ranking animals tend to adopt one of two strategies," she says.
"You have got the animals who accept their station in life and then you have got the other ones that are continually trying to climb, and as a consequence, their life is very stressed."
The research involved watching pigs for hours on end. Cameras were installed in the piggeries to help track the daily lives of piglets, adolescents and adults.
It soon became clear, that just like humans, no two pigs are the same and all sorts of philosophies and lifestyle strategies are adopted by the inhabitants of the piggery in a bid to get the most out of life.
Some pigs, often the meek and physically weaker animals, decide to opt for as little confrontation as possible.
Rather than pushing and shoving to get their snout into the feeder, they will wait until the others have fed. Some will even wait until after dark to feed, with the prospect of a quiet stress-free meal being worth enduring hunger pangs.
Contrast that style with the born fighters who contest everything, even the best lying space with their peers.
Researcher Niamh O'Connell looked at pigs' early experiences
These pigs have ambitions to be high status individuals.
When the feed arrives, these pushy pigs are determined to get their full share - and now. They push, they squeal and it may be stressful, but that's life, right?
Surprisingly the stress addicts are not always the biggest pigs in the pen.
But what they lack in size, they make up for with sheer aggression.
Sadly for them, they will probably never make it to the top of the social ladder - the bigger, smarter pigs see to that - but these pushy pigs are prepared to endure high levels of stress in an endless battle to improve their social standing.
The scientists have been asking where all this aggression comes from.
Were these pigs born pushy or had their life experience shaped the sort of animals they had become?
Niamh O'Connell decided to look into the pigs' formative years to see if early life experiences could be responsible.
The young scientist was looking for early influences in the development of the pigs' personalities. The results were startling.
The contrast in behaviour of animals from good and bad homes was clear to see.
The researchers wanted to discover what makes certain pigs pushy
Pigs reared in comfortable, stimulating backgrounds developed into adults who regulate their societies in a much less aggressive fashion.
On the other hand, pigs from impoverished and barren environments grew up to be much more aggressive and bullying.
Again, the human parallels were striking.
And when the research team looked more closely at what was needed to produce a well-adjusted pig, they found that piglet play had a key role in developing good social attitudes.
"This is a very important learning tool for children and also for farm animals - you learn through playing how to interact with other animals, what are your strengths and weaknesses and when to stop," said Niamh O'Connell.
The pig study was yielding interesting insights but there was more to come.
The research had established that a good early life experience helped produce pigs who would develop stable, peaceful adult groups.
And there was another discovery - the peace dividend.
The study indicated there were some striking human parallels
For a young gilt brought up in a stable group, the scientists found that she in turn would tend to be a good mother.
The scientists had found a heartening and life-affirming fact - that tenderness and care experienced as a piglet will in turn be bestowed on the next generation.
And more proof was to follow in the study of adolescent pigs. Those from good backgrounds are less likely to get involved in anti-social activity.
But what about those pushy pigs - can love and good mothering help save the stress junkies?
Well, only to an extent. Pushy pigs it seems are victims not so much of their environments but of their own forceful personalities.
Being part of a stable group will help, but a pushy pig it seems will always be a pushy pig.
Again the human parallel is striking.