KEY POINTS:
My sister and I are great friends. Being in the same house over the holidays made us both very happy, which made everyone around us very happy.
Unhappily for us, it did nothing for our waistlines, which expanded in direct proportion to our enjoyment.
"You have to go home," she said finally. I really did. We were having too good a time.
Then there's my Irish-Scottish friend, who returned to Aotearoa recently. She read me poetry - Robbie Burns as he was meant to be read - while we drank liberal quantities of her favourite beverages: tea, and bubbly mixed with orange juice. As our moods soared, so did the reading on my scales.
"I'm worried about the influence of your peers," my teenager mocked.
All right, so it's not only teenagers who are influenced by their friends. According to research reported by the New Scientist, grown-ups are just as susceptible. The new adage, they reckon, is: We are who we hang out with.
Indeed, the sphere of influence - on the way we feel and even the way we behave - extends beyond our friends and relatives to the friends of friends, and even to their friends' friends. In other words, people three degrees of separation from us who we have never met.
Say hello to emotional contagion, where feelings and behaviours can spread through social networks much like a highly contagious virus.
As New Scientist reports, "it is becoming clear that a whole range of phenomena are transmitted through networks of friends in ways that are not entirely understood: happiness and depression, obesity, drinking and smoking habits, ill-health, the inclination to turn out and vote during elections, a taste for certain music or food, a preference for online privacy, and even the tendency to attempt or think about suicide".
Some of this we knew already. If someone smiles at us, we instinctively smile back - and feel better for it. We feel uplifted after we've been in the company of people we like, while the company of others can drain us of the will to live. Psychologists have shown that we unconsciously mirror the facial expressions, speech and mannerisms of the people we're with in an empathetic mimicry that sets off a kind of neural feedback in our brains - and as we act, so we feel.
Which is potentially good news. If we understand how certain behaviours and emotions are spread, we stand a chance of determining which ones we catch or pass on.
Take happiness, which a number of studies have shown is critical for our health and sanity.
We all know that people with more friends are happier, but a recently published study shows that what really matters is whether those friends are happy. Our chances of happiness increase the better connected we are to happy people.
As the study's authors, Nicholas Christakis and James Fowler, noted in the British Medical Journal in December: "Most important from our perspective is the recognition that people are embedded in social networks and that the health and wellbeing of one person affects the health and wellbeing of others ... Human happiness is not merely the province of isolated individuals."
We don't get there on our own - and anyone who says otherwise is either lying or deeply unaware. Human beings are inherently social creatures, and, according to the relatively new field of social neuroscience, reliant on social connections in ways that we hardly imagined.
The American psychologist Daniel Goleman, who wrote the best-selling Emotional Intelligence and Social Intelligence: The New Science of Human Relationships, says science is providing the neural basis for what we've always known: human beings are wired to connect with one other.
"Neuroscience has discovered that our brain's very design makes it sociable, inexorably drawn into an intimate brain-to-brain link-up whenever we engage with another person. That neural bridge lets us affect the brain - and so the body - of everyone we interact with, just as they do us."
So relationships have the power to influence not only our moods but our brain chemistry - stimulating our nervous systems and affecting hormones, heart rate, circulation, breathing and the immune system.
Our social interactions matter - insults can be toxic to our systems, and love healing.
Physical proximity matters, too, which means those hundreds of friends we claim to have on social networking websites such as Facebook or MySpace probably don't provide the social nurturance our brains seem to crave.
In fact, after looking at the profiles of hundreds of students on Facebook, Professors Christakis and Fowler deduced from their photos that despite boasting an average of 110 "friends", most had only six real friends.
Also that those who smiled tended to be at the centre of their social network, rather than at the periphery.
Science is beginning to show us how we might become better parents, teachers, lovers, friends; and which part of the brain we need to appeal to in order to infect people with healthy habits.
It can also help to explain why putting troubled kids together in, say, a boot camp, is more likely to reinforce the behaviour that got them there than putting them among people who can influence their brains for the better.
People like Social Development Minister Paula Bennett, who's under fire for trying to help her daughter's boyfriend - a kid with a violent past - avoid jail.
The science tells us she'd have had a better chance of changing him than the prison sentence he's currently serving.
tapu.misa@gmail.com
