The level of affection expressed by women, to an extent, can be explained 45 per cent by hereditary, and 55 per cent by environmental influences like media, personal relationships, and other unique life experiences. However, genetics do not appear to influence how affectionate men are, according to a study published in Communication Monographs? and led by Kory Floyd, a professor in the University Arizona Department of Communication in the College of Social and Behavioural Sciences.
"The question that drove the study was: Recognising that some people are more affectionate than others, what accounts for that variation, and is any part of that variation genetic," questioned Floyd, whose research focuses on the communication of affection in close relationships and its effects on stress and physiological functioning.
"A study like this makes room for us to talk about the possibility that a number of social and behavioural traits that we automatically assume are learned may also have a genetic component," Floyd added.
Floyd and his collaborators studied 464 pairs of adult twins about half identical and half fraternal between the ages 19 and 84.
Twin studies often are used to look at how environmental and genetic factors influence specific traits. Because twins typically are raised in the same household, they've usually had very similar upbringings and early experiences.
However, twins' genetic similarities vary based on what type of twins they are. While identical twins share 100 per cent of their genetic material, fraternal twins share only 50 per cent the same as regular siblings.
Each participant in the study rated a series of statements designed to measure how much affection they typically express. The researchers then looked at how similar each twin pair's responses were.
The identical twin pairs scored more similarly than the fraternal twin pairs at least in the case of women suggesting that there is, in fact, a genetic component to affectionate behaviour.
The researchers don't know why affectionate behaviour seems to be heritable in women but not men.
However, Floyd notes that men, on average, tend to express less affection overall than women, as evidenced by previous research.
"When we measure people's tendency to be affectionate and to receive affection from other people, almost without exception we find that women score higher than men," Floyd said.
"The trait of being affectionate may be more adaptive for women in an evolutionary sense. There is some speculation that affectionate behaviour is more health support for women than it is for men, and that it helps women to manage the effects of stress more than it does for men. That may be partly why women are more likely than men to inherit the tendency to behave that way rather than that tendency simply being a product of their environment," Floyd added.
The researchers also found that twins' shared environment such as how they were raised or their socioeconomic background had little bearing on how affectionate they were. Rather, unique environmental factors, such as an individual's friends and experiences apart from their twin, were what mattered more.
"Our genes simply predispose us to certain kinds of behaviours; that doesn't automatically mean we're going to engage in those behaviours. And it certainly doesn't mean that we have no control over them," Floyd said.