When Nate Yoder was a child, his parents made him write and eat with his right hand, but he kept switching back to his left.

“It’s the way I’ve grown up,” said Yoder, senior in sociology. “It’s probably scientific – involved with how the brain works.”

Brandi Kliegl, senior in psychology, disagrees.

“I don’t think [handedness] has anything to do with [the brain]; it’s probably just luck,” Kliegl said. She writes with her left hand, but throws with her right.

Janet Heintz, occupational therapist for the Ames Area Education Agency believes, using the left hand is a “true dominance formed prior to birth.”

By the age of two and a half, most children have shown a hand preference by feeding themselves, grasping, and reaching with a single hand.

Brian Brooks, temporary instructor of psychology, has looked into the right-versus-left hand issue and does not believe there is a true left-handedness.

“[Left-handers] might show some benefit for left hand over right, but not nearly to the degree of people who are right-handed.”

He said it is a degree of left-handedness and a degree of hand dominance.

“There are people who are more left-handed, but really, there are a lot more people who are right-handed,” Brooks said. “There may be a few people that are 100 percent left-hand dominant, but that is questionable – most research suggests those people aren’t as left-handed as the people who are right-handed are right-handed.”

Brooks said there are many theories as to why a child might be left-handed, though it is mainstream to believe in right brain/left brain differences. He said the question is what causes this brain difference.

“One theory that has received a significant amount of support deals with the direction the ear of the fetus in the womb faces,” Brooks said. “Most fetuses have their right ear facing out of the womb, therefore more language input prenatally is delivered through the right ear.”

The right ear projects more strongly to the left half of the brain, which would predispose the child whose right ear faces out to have language centers in the left hemisphere of the brain, Brooks said. The left hemisphere of the brain controls the right hand.

“But sometimes, the fetus will be positioned opposite and the left ear will be facing out, making it more bilateral or right hemisphere-dominant for language,” Brooks said. This situation would correlate with left-handedness.

“If you look at twins, they are more likely to be discoordinate with respect to handedness,” Brooks said. “One twin will be more likely to be right-handed and the other left-handed because twins are more likely to be opposite with how they lie in the womb.”

Another theory deals with the level of testosterone in the womb.

“There is some evidence that if there is an excess of testosterone in the womb it causes more bilaterally distributed language centers across the brain,” Brooks said. People with bilaterally distributed language centers are more prone to left handedness.

Brooks also said one possible reason for handedness is a genetic predisposition – with left-handedness running in the family.

He said that while there is some evidence left-handed people are more accident-prone and have higher death rates and shorter life spans, it may be due to living in a right-handed world.

– Dana DeJong contributed to this story