Having a male co-twin improves mental rotation performance in females

September 7, 2010, Association for Psychological Science

Having a sibling, especially a twin, impacts your life. Your twin may be your best friend or your biggest rival, but throughout life you influence each other. However, a recent study published in Psychological Science, a journal of the Association for Psychological Science, shows that having an opposite-sex twin may impact you even before you are born: females with a male co-twin score higher on mental rotation task than females with a female co-twin.

Males, as young as three months of age, outperform females on mental rotation tasks, tests that require rotation of three dimensional objects in mental space. has been suggested to account, at least partially, for sex differences in this task suggesting that females with exposure to higher levels of prenatal testosterone may perform better than females with lower levels of testosterone.

Eero Vuoksimaa from the University of Helsinki and co-authors assessed the possible prenatal masculinization of spatial ability in females with a male co-twin. "Earlier studies have tested the possible masculinization of females with a male co-twin, but the measures in those studies have not always been ideal," says Vuoksimaa. "If prenatal masculinization does occur in female twins from opposite-sex pairs, it would be expected to be most evident in behaviors that are related to testosterone levels and show a large and robust male advantage, such as the mental rotation task."

For the study, mental rotation task scores between twins from same-sex and opposite-sex pairs were compared. Not surprisingly males scored higher than females, but females with a male co-twin scored higher than did females with a female co-twin. In contrast, there was no difference in the mental rotation task performance of males from opposite-sex and same-sex pairs.

For females with a twin brother, determining if differences in performance are due to prenatal exposure to testosterone or due to their tendency to engage in more male-typical activities is still unclear. "While our results are consistent with the prenatal masculinization hypothesis," says Vuoksimaa, "girls who grow up with a twin brother experience a different social world than girls growing up with a twin sister. We cannot exclude effects of post-birth socialization."

However, the psychological scientists included a computer game task in their study, a possible indicator of practice effects. "Interestingly, computer game playing experience was not related to mental rotation test performance in our study," says Vuoksimaa. This suggests that the results are not fully explained by postnatal environment, but the route for masculinization of mental rotation ability remains unknown. "More research is needed to disentangle the origins of the masculinization of performance in with a male co-twin."

Related Stories

Recommended for you

WHO recognises 'compulsive sexual behaviour' as mental disorder

July 15, 2018
The World Health Organization has recognised "compulsive sexual behaviour" as a mental disorder, but said Saturday it remained unclear if it was an addiction on a par with gambling or drug abuse.

How looking at the big picture can lead to better decisions

July 13, 2018
New research suggests how distancing yourself from a decision may help you make the choice that produces the most benefit for you and others affected.

Nature is proving to be awesome medicine for PTSD

July 13, 2018
The awe we feel in nature can dramatically reduce symptoms of post-traumatic stress disorder, according to UC Berkeley research that tracked psychological and physiological changes in war veterans and at-risk inner-city youth ...

Is depression during pregnancy on the rise?

July 13, 2018
(HealthDay)—Today's young mothers-to-be may be more likely to develop depression while pregnant than their own mothers were, a new study suggests.

Machine learning helps to predict the treatment outcomes of schizophrenia

July 12, 2018
Could the diagnosis and treatment of mental health disorders one day be aided through the help of machine learning? New research from the University of Alberta is bringing us closer to that future through a study published ...

Mental illness study to explore patients' self-assessments

July 12, 2018
As the mental health community pursues new ways to improve the lives of the severely ill, a University of Texas at Dallas researcher is focusing on what can be learned from patients' answers to a simple question: "How do ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.