Infant Handedness: Baby Field Notes a Lefty?

A greater preponderance of left-handed U.S. Presidents aside, it has me concerned, a little, that Baby Field Notes might turn out to be a lefty. She's showing what I would call a strong preference for sucking her left hand, moving her left hand more, and holding things longer with her left hand.

The first question I had was whether there's any research to suggest that early hand preference correlates with handedness later. I'm still doing the research, but so far I've turned up some interesting stuff, all published in reputable journals like Developmental Psychobiology and the International Journal of Primatology.

Handedness is associated with brain lateralization and specialization, meaning that the two hemispheres are not exactly alike. The right and left hemispheres execute different functions. For example, most people process language in their left hemispheres. Spatial reasoning, such as mental rotation of objects, is processed in the right hemisphere. Although it's not a perfect relationship, the vast majority of right-handers (90%) process language in their left hemispheres, but only about 70% of left-handers do. A higher proportion of left-handed people process language in the wrong hemisphere, or both hemispheres. It's also said that they are more likely to be dyslexic.

Nonhuman primates are generally not thought to have much language capacity (there are exceptions!). They are also thought to not show much evidence of brain laterality, i.e. their cerebral hemispheres are more symmetrical in function and do not show a left hemisphere specialization for language (there are exceptions!). Furthermore, they are not thought to show a hand preference, i.e. they don't preferentially grasp or manipulate stuff their right hands (there are exceptions with this too!).

What all this means is that other apes don't have the amazing language abilities that humans have because they don't have the brain circuitry specialized for such a complex task and their lack of hand preference is one piece of evidence for that. However, I think that there is plenty of evidence that other apes have some language capacity and that it's likely early human ancestors (6 million years ago) also had language capacity. The human ability to write and recite nursery rhymes didn't just appear out of nowhere, it built upon earlier capabilities.

Left-hand preference may be just one symptom of something gone haywire in brain circuitry regarding language development given the links between the hemisphere dominance, handedness and language processing. In other words, it's not too surprising that more lefties would have language difficulties and I hope that Baby Field Notes doesn't! Language stuff aside, it would make life a lot easier for her to not have to deal with the hassles that lefties encounter.

A good example would be the rotary paper cutter we have. It, like the vast majority of paper cutters, is set up for right handers. The blade is on the right side and the grid and platform to rest the paper on is to the left. For a left handed person to use it, they would have to either operate the blade with their clumsier hand, or, they'd have to hold the paper with their right hand and reach across their right wrist and hand to grasp the arm or blade to cut the paper with their left hand — a recipe ripe for making a mistake and winding up injured.

Speaking of language I find it interesting that the word dexterous, meaning nimble or skillful, comes from the word dexter, which means right. The dexter hand is the right hand. In contrast, left in French is gauche, which in English means clumsy or boorish. Compliments that have a subversive, not so nice element to them are left-handed compliments. I'm just saying, left handers don't just die earlier (as research has found), our whole language schema paints them in a poor light.

However, left handedness/right brain dominance is also associated with being gifted analytically, particularly in mental rotation and three-dimensional problem solving.

In an effort to find out whether early left hand preference is associated with being a lefty, I skimmed a bunch of journal abstracts, and although I haven't yet found an answer, I did learn some other interesting stuff.

At just 5 months gestation, fetuses already show brain lateralization. Using ultrasound imaging, researchers measured the size of both lobes of the brain of around 100 fetuses and found that their left hemispheres were larger than their right hemispheres. Also interesting is that the girls had larger brains.

Fetuses suck their thumbs in utero, no surprise there, but they also show a preference for sucking their right thumb and this can show up as early as 15 weeks of gestation. Also, research on some primate species, including both monkeys and two kinds of apes (bonobos and chimps) has found that they have a nipple preference — left — which is also associated with a preference for turning their heads to the right, which would be toward the left breast when being carried and while suckling. What's noteworthy too, is that nonhuman primates and humans both show a bias for left-handed infant carrying and cradling.

Early on, BFN preferred the right boob, the atypical pattern. I also have a strong preference for carrying her and cradling her in my right arm. Mr. Field Notes does it in the more usual primate fashion — with his left arm — and was the first to observe that I don't. So I guess I am odd and maybe Baby FN is too.

In any case, Baby Field Notes may indeed turn out to be a lefty, and it's not likely I will be able to change that if she is. Handedness is not learned, a plethora of research suggests. Instead, it is "a spontaneous expression of the developing nervous system unaffected by the environment," as Dr. Johanna de Vries put it best.

However, other researchers, such as William Hopkins, point out that behavior can influence brain development, so use of the right hand can theoretically cause the brain to develop asymmetrically. [I think there's some merit to that, but how likely is the preference of right hand use to be just chance?] I think it's more likely hand preference is genetically determined and there's a good chance that no amount of me putting things in Baby Field Notes right hand will change anything if she is indeed a lefty.

My intuition is also that she is likely to be a lefty, given her hand preference now.