Stockholm, Sweden. The attitudes of families and the public exert little impact on adult decisions to have sex with persons of the same or the opposite sex. Instead, findings from the largest study in the world so far point to hereditary factors and individual experiences as the strongest influences on our choice of sexual partners.

The conclusions apply equally well to why people only have sex with persons of the opposite sex as to why we have sex with same-sex partners. However, the conclusions are more difficult to transfer to countries where non-heterosexual behaviour remains prohibited.

The study from the Swedish medical university Karolinska Institutet (KI) was performed in collaboration with the Queen Mary University of London. More than 7,600 Swedish twins (men and women) aged 20-47 years responded to a 2005 - 2006 survey of health, behaviour, and sexuality. Seven percent of the twins had a same-sex sexual partner.

"The results show, that familial and public attitudes might be less important for our sexual behaviour than previously suggested", says Associate Professor Niklas Långström, one of the involved researchers.

"Instead,

Flint, MI, USA. Having a husband creates an extra seven hours a week of housework for women, according to a University of Michigan (U-M) study of a nationally representative sample of U.S. families. For men, the picture is very different: A wife saves men from about an hour of housework a week. The findings are part of a detailed study of housework trends, based on 2005 time-diary data from the federally-funded Panel Study of Income Dynamics (PSID), conducted since 1968 at the U-M Institute for Social Research (ISR).

For the study, researchers analyzed data from time diaries, considered the most accurate way to assess how people spend their time. They supplemented the analysis with data from questionnaires asking both men and women to recall how much time they spent on basic housework in an average week, including time spent cooking, cleaning and doing other basic work around the house. Excluded from these "core" housework hours were tasks like gardening, home repairs, or washing the car.

The researchers also examined how age and the number of children, as well as marital status and age, influenced time spent doing housework.

Single women in

Nottingham, UK. How do people co-operate for the common good and what happens when they don't? To work or act together is to cooperate, but the antithesis is competition, the rivalry of two or more parties over something. However, people can be cooperative or competitive in turn, depending on the circumstances. Economists have studied the extent to which some people will sacrifice personal gain to benefit the wider public, while 'freeloaders' try to take advantage of their generosity.

In a new international study of 16 countries, the researchers found that marked national differences arose when freeloaders were punished for putting their own interests ahead of the common good. And whether they accepted punishment or retaliated in kind depended on what kind of society they lived in.

Antisocial Punishment Across Societies. Benedikt Herrmann, Christian Thöni, and Simon Gächter. Science 7 March 2008 319: 1362-1367. doi: 10.1126 / science.1153808.

In countries like Switzerland, the UK, and the USA, freeloaders accepted their punishment and became much more co-operative. But in countries based