Letters

Right-left preference
In the article “Body in mind” (SN: 10/25/08, p. 24), Dr. Casasanto speaks of results with people who are left-handed or right-handed. But no mention is made of people who are innately ambidextrous, as in my family. Has he worked with any of these people? What about people who are almost ambidextrous but not totally? I notice the quality runs in families, but since it is stronger or weaker depending on the individual, I would conclude several genes play a role.
Tana Hemingway, Mesquite, N.M.

“Everyone falls somewhere along a continuum from right- to left-handed,” says Daniel Casasanto of the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands, whose research suggests people with different kinds of bodies think differently about abstract concepts. “Someone’s degree of handedness should influence how strongly they show a preference for their dominant side: Strongly handed people (whether left or right) should show a stronger preference, and weakly handed people, close to ambidextrous, should show a weaker preference. In principle, a perfectly ambidextrous person should show no body-specific preference for things on the left or right — but lots of other factors, in addition to handedness, also influence our judgments.” — Bruce Bower

Vitamin D and peanuts
At first glance the study described in “Food advice could be peanuts” (SN: 12/6/08, p. 8) seems to control for a single variable. Two equal groups have one difference — exposure to peanuts at an early age and at a later age. Let me suggest that there is another difference. The children of Israel received a great deal more sunlight and therefore more vitamin D than the children in England. Vitamin D improves immune function, and higher levels would mean fewer problems dealing with peanuts.
Bruce Bennett, Watertown, N.Y.

The researchers accounted for several differences between the British and Israeli groups, including age, the existence of other food allergies and any propensity to develop asthma or skin rashes. After adjusting for these factors, the greater incidence of peanut allergy in the British children still stood out. The British children were also clearly more apt to be allergic to tree nuts, but not to sesame, milk or eggs. The researchers didn’t account for sun exposure or vitamin D levels. — Nathan Seppa