We've probably all encountered a narcissist.
They're typically arrogant and extroverted, think they're special and entitled, are remorseless in taking advantage of others, crow about sexual conquests and are big on flings.
Now researchers have asked an interesting question: are they interested in your significant other?
A study out of the US has found while narcissists don't necessarily target those already spoken for, that doesn't stop them when they want to.
"I thought it was possible that there might be something appealing about the game of mate-poaching that might appeal to narcissists, because they are known to play games," said Amy Brunell, an associate professor of psychology at Ohio State University.
But evidence of that type of pattern didn't turn up. Study participants with narcissistic traits reported that they have - with greater frequency than people who aren't narcissists - attempted to pursue relationships with someone who is in an existing relationship, Brunell said.
But that wasn't necessarily because the person was taken.
"They seem to not discriminate between those in relationships and those who are single," she said.
"It could be that they just go after whoever appeals to them without regard for relationship status."
Previous research had shown that people in general - not just narcissists - tend to perceive others who are in relationships as more desirable.
Combine that with the traits of narcissism, Brunell figured, and you might have a recipe for aggressive "mate poaching" - the scientific term for making a play for someone already in a relationship.
Her research pointed to an overall trend: narcissists were more likely to engage in mate poaching, but not more interested in people already in a relationship - with the exception of opportunities for a quick hook-up.
"Understanding the behaviour of narcissists is important because it helps us better understand the people who are in our lives - and the types of people we don't necessarily want in our lives."
Fortunately, there might be less chance of a bumping into a narcissist here.
Despite the advent of Instagram selfies and reality TV, other research has found Kiwis are a relatively humble bunch, with just one in 10 of us holding traits that could be considered narcissistic.
Why the smart succeed
If you're smarter, you get ahead easier.
That's according to an international team of researchers who came up with a series of games to find out which factors lead to co-operative behaviour in and outside work.
Their findings showed people with a higher IQ displayed "significantly higher" levels of cooperation, which in turn led to them earning more money as part of the game.
The failure of individuals with lower intelligence to appropriately follow a consistent strategy and estimate the future consequences of their actions accounted for these different outcomes.
Personality traits – such as agreeableness, conscientiousness, trust and generosity - also affected behaviour, but in smaller measure, and only initially.
The researchers concluded that a society was cohesive if people were smart enough to be consistent in their strategies, and to foresee the social consequences of their actions, including the consequences for others.
"We wanted to explore what factors make us effective social animals," explained study co-author Professor Eugenio Proto, of the University of Bristol.
"In other words, what enables us to behave optimally in situations when cooperation is potentially beneficial not only to us, but to our neighbours, people in the same country or who share the same planet."
People might naturally presume that people who are nice, conscientious and generous are automatically more cooperative, he said.
"But, through our research, we find overwhelming support for the idea that intelligence is the primary condition for a socially cohesive, cooperative society.
"A good heart and good behaviour have an effect too but it's transitory and small."
An extra benefit of higher intelligence shown in the experiment, and which the researchers expected was likely in real life, was the ability to process information faster and to learn from it.
"This scenario can be applied to the workplace, where it's likely that intelligent people who see the bigger picture and work cooperatively, will ultimately be promoted and financially rewarded."
The researchers say their findings have potentially important implications for policy, especially in the education and trade sectors.
When we fight, we can hurt our kids
What do everyday parental spats mean for kids?
New research shows the emotional processing of exposed children can be affected, far down the track.
It could even make them over-vigilant, anxious and vulnerable to distorting human interactions that are neutral in tone, throwing them off-balance interpersonally as adults.
"The message is clear: even low-level adversity like parental conflict isn't good for kids," explained psychology researcher Alice Schermerhorn, an assistant professor at the University of Vermont.
In the study, 99 children aged 9 to 11 were divided into two groups based on a series of psychological assessments they took that scored how much parental conflict they experienced and how much they felt the conflict threatened their parents' marriage.
Children were then shown a series of photographs of couples engaged in happy, angry or neutral interactions and asked to choose which category the photos fit.
Children from the low-conflict homes consistently scored the photos accurately.
Those from high-conflict homes who experienced the conflict as a threat were able to accurately identify the happy and angry couples, but not those in neutral poses - incorrectly reading them as either angry or happy or saying they didn't know which category they fit.
Schermerhorn saw two possible interpretations of the results.
The inaccuracy could be down to hyper-vigilance.
"If their perception of conflict and threat leads children to be vigilant for signs of trouble, that could lead them to interpret neutral expressions as angry ones or may simply present greater processing challenges," she said.
Alternatively, it could be that neutral parental interactions may be less significant for children who feel threatened by their parents' conflict.
"They may be more tuned into angry interactions, which could be a cue for them to retreat to their room, or happy ones, which could signal that their parents are available to them," she said.
"Neutral interactions don't offer much information, so they may not value them or learn to recognise."