As an engineering lecturer, I find it fascinating that a much larger proportion of the students I teach are left-handed compared with the estimated 10 per cent of left-handers in the population. Could it be that left-handed students are more likely to study engineering, or is it just coincidence that up to 30 per cent of the students I teach are left-handed?
Our hand preference has been shown to exist before we are born, with ultrasound studies showing that by the 13th week of pregnancy 10 per cent of unborn babies preferentially suck their left thumb instead of their right, the same percentage that goes on to be left handed in the population.
We are not unique in our handedness preference, other primates, including chimpanzees, show a preference for one hand over the other when using tools; however, their split is a much more even 50/50. Even animals that don't have hands show a preference, with mice having left and right paw preferences, and tree frogs preferentially jumping away from their predators in one direction over another.
I still don't know the answer to my student question, but research out this week could help me to determine a theory. Published in the journal Frontiers in Psychology, the study tried to determine whether being left-handed was a sign of giftedness in mathematics. This relationship has been studied before, with previous researchers disagreeing with some finding that left-handed people perform better, and some worse in mathematics base tests. This new study assessed the mathematical abilities of more than 2300 students aged from 6 to 17 in Italy using five different tests. The researchers found that the left-handers outperformed the right-handers only when solving difficult mathematical problems but that there was no significant difference for those doing simple arithmetic. As the entry criteria for engineering degrees requires excellence in advanced mathematics at high school, this new study could help with my explanation to why there are more left-handed students in my class.
The cause of handedness is still unclear - previously scientists thought that gene activity in the different hemispheres of the developing brain determined which hand would be dominant. However, a more recent theory published in the journal eLife used tissue testing to determine that handedness is more likely to be determined by gene expressions found in the developing spinal cords of growing babies rather than their brains. They also found that these spinal cord gene expressions were not traits inherited from their parents, but instead, expressions influenced by environmental factors that the pregnant mother was exposed to. Although the exact environmental factors were not able to be determined, scientists believe through epigenetics that a mother's nutrition, mental health and lifestyle can alter how enzymes operate around her developing baby, which can change how genes are able to express themselves in the fetal spinal cord.
It's not just our hands that show a preferential side, we show dominance in many areas. To determine your dominant eye, extend your arm out and place your thumb and forefinger together to make a circle. With both eyes open, look through the circle and move it until a far-off object such as a clock or a doorknob is in the centre of the circle. Now close your left eye, if the object remains in the centre of the circle you have a dominant right eye, if the object seems to move, you are left-eye dominant. Your dominant ear is likely to be the one you hold a phone up to and the next time you kick a football, stop to take a look at the dominant leg that you chose to use.