Are You Mixed-Handed?

You may be using your non-dominant hand more than you realize but what, if anything, does that mean?

I’ve always considered myself to be right-handed but over the last 15 years, I’ve come to realize I’m actually mixed-handed—I use my right hand exclusively for most things but for some tasks, I use my left hand exclusively. This discovery has made me curious about what being mixed-handed means and what causes it—but also, how many other people, like me, have blithely assumed they were right- or left-handed, without realizing they were using their non-dominant hand for certain tasks.

In June 2009, as I mentioned here, I broke my left shoulder (snapped my humerus just below the ball-joint that fits into the shoulder socket). This put me in what’s called an immobilizing sling for 6 weeks, which meant I couldn’t move my left arm at all, or use my left hand for much of anything. It was excruciatingly painful and required months of agonizing rehab for the shoulder joint after the bone had healed.

Everyone said, “You’re lucky it wasn’t your right arm.” Fine for them to say, but what I noticed was how incapacitated I felt, especially in the kitchen. Not being able to use my left hand at all limited my ability to function much more than I anticipated.

Part of this was due to not being able to use my left hand to stabilize objects during cutting, like a tomato. Another was the built-in “handedness” of the kitchen itself: how awkward it was to turn on the hot water tap, and open left-hinged cupboard doors, with my right hand. However, I also found it oddly awkward to pick the squishy, half-rotten blueberries out of a container of fresh berries with my right hand—I could do it, but not very fast or efficiently. I also realized I take items out of cupboards with my left hand and use my left hand again when putting plates and cutlery away: doing these things with my right hand just felt wrong.

Furthermore, once I’d healed sufficiently to do without the sling for the broken bone—but before my muscles had recovered—I noticed something else. I simply didn’t have the strength in my left arm to peel a banana or an orange—or to pull the husks from a cob of corn. Just as for the plucking out individual blueberries business, I could do the peeling with my right hand but it took effort and concentration—and felt decidedly unnatural.

More importantly, I simply had not realized I’d been doing all of these activities with my left hand until those moments. For example, I remember standing in the grocery store feeling a bit stunned as I tried to shuck an ear of corn, wondering why I was trying to pull the husks with my left hand when every other person around me was using their right hand.

Here’s some background: my father was left-handed but was forced in school to use his right, so as an adult, could use either hand for many tasks. My mother was right-handed.

Family lore has it that my mother suspected early on that my my older sister was left handed and decided to use the needle-and-thread test. A right-handed person holds the thread in their right hand and the needle in their left, and pushes the thread through the eye of the needle (that’s how I do it).

While my sister held the needle and thread correctly for a right-handed person, she used her left hand to guide the eye of the needle onto the thread. While it might have been that this task was simply too advanced for a three-year-old, my mother suspected stubbornness: that my sister was actually left-handed but insisted on copying how she (my right-handed mother) did things.

My sister became notorious in the family, and at elementary school, for her uncoordinated attempts at certain tasks, like sweeping with a broom, but was also playing the piano competently with both hands by the age of four. Over time, she easily learned to write and cut with scissors using her right hand—and became an excellent pianist.

My childhood experience with handedness was somewhat different. Although no one had ever suggested I might be left-handed, I noticed myself that I was doing some things differently than my right-handed friends and family members. The first was walking a bicycle.

My mother always complained about the grease on my pants: that because I stood on the right side to walk my bike, I was constantly rubbing up against the greasy chain. She strongly suggested I walk on the other side. But even though everyone around me (presumably right-handed) walked on the left, I found I had trouble controlling the handlebars from that side and it felt really awkward. I don’t think my mother ever considered that walking a bike had a “handedness” component, but Grok confirms it does.

Yet, I hold a broom like most right-handed people do, with my right hand on top and unlike my sister, never had any trouble sweeping smoothly and efficiently.

A second big discovery came in high school, when I realized that I couldn’t do what my fellow students were doing at their lockers: holding the body of the combination lock in the right hand and twirling the dial with their right fingers. But after watching my left-handed locker-neighbour doing it, I found I could twirl the dial with my left hand, just as fast and smoothly as most of the others were doing with their right.

About a year or so after my broken shoulder experience, I was talking with my sister about this handedness issue and we found a test for handedness called the Edinburgh Handedness Inventory.

For the following 10 activities, you indicate whether you use your primarily your right hand, left hand, or both. At it’s simplest, you get +10 points for each “strongly right-handed” answer, and -10 for each “strongly left-handed” answer, out of a total 100 points.

1. Writing

2. Drawing

3. Throwing

4. Using scissors

5. Brushing teeth

6. Using a knife (without a fork)

7. Using a spoon

8. Striking a match

9. Opening a box or lid

10. Using a broom (upper hand)

I scored 90, since it turns out I also take the lids off jars (#9) with my left hand (something else I never realized I did). My sister scored 80, loosing 10 points for the jars (like me) but also for the broom business (no surprise there!).

As I recall, I tested both of my children using this list and both came out exclusively right-handed.

One study that tested six-year-olds for handedness used these criteria:¹

1. drawing

2. buttering bread

3. holding a toothbrush

4. using scissors

5. holding a fork or spoon

6. holding an ice cream

7. taking sweets from a bag

8. throwing a ball

I find this interesting because out of this truncated list of eight activities modified for children, I do two left-handed (6, holding an ice cream and 7, taking sweets from a bag) and would be classified as mixed-handed. However, the list of 11 criteria they used for adults in the same study would not have identified any of the tasks I do with my left hand and would therefore have missed my mixed-handedness.

Just last year, after coming across a different test for handedness, I also realized I deal and shuffle cards with my left hand. This came as quite a shock because not only had I not realized I’d been dealing left-handed my entire life but apparently no one in my family noticed either.

In the questionnaire copied below, I would score 20/24 for right-handedness because of my “always” answer to questions 9 and 12 (2 points each), as would my sister (for 4 and 12), who perversely deals cards with her right hand. We were a card-playing family growing up and I wonder if our right-handed mother taught my sister to deal and shuffle, while our left-handed father taught me. Or, that I learned by watching how my father dealt and shuffled. However, they’re both gone now, so we’ll never know for sure.²

It’s also interesting that neither the walking a bike or one-handed combination lock manipulation are activities mentioned in any of these tests (perhaps to be more applicable to all) but oddly, neither is the peeling fruit task, which I’d have thought would be an almost universal activity. I’ve seen other lists with up to 36 tasks that don’t mention these three either, but many do include a “picking up a coin” that probably covers the plucking rotten berries job.

More handedness surprises were in store for me last Christmas. First, I tried to use a new small saucepan (shown above), to pour a cooked glaze over a cake but found myself holding the little pot in my left hand, which put the spout on the wrong side. I don’t think I always pour with my left hand, but for this task, I definitely wanted to go left. Then I realized I hold my coffee cup in my left hand, which made the new travel mug I received as a gift awkward to use because the drinking spout was positioned for right-handed holding. These tasks don’t tend to show up on the handedness tests either.

In other words, according to most of the handedness tests, I’m right-handed but not strongly so; I’m mixed-handed but not strongly so.

Apparently, as the graph below from the same Briggs and Nebes study of handedness in college students shows, in general most of these students were like me (the far right side of the graph): they always did most things with their right-hand hand but always did a few things with their left. Although far fewer students tested in this study (as for the general population) were strongly left-handed, many of them similarly did a few things exclusively with their right hand (left side of the graph).

In contrast to other studies, in this one only students that scored in the very middle (-9 to +8) were classified as mixed-handed: most tests considered even one activity performed with the non-dominant hand to be an indicator of mixed-handedness. However, it’s apparent from this graph that very few of these students were strongly mixed handed to the point where they did roughly half of the listed tasks with their non-dominant hand (middle of the graph). Although I’m sure that a more thorough literature search would reveal other studies with different numbers, I expect the overall pattern would be similar to this.

Note the term ‘ambidextrous’ is sometimes used to mean mixed-handedness but traditionally is reserved for the ability to use both left and right hand with equal proficiency for the same task, such as writing. People who are naturally ambidextrous are actually quite rare, comprising about 1% of the population, with some research suggesting that these individuals are actually just less strongly left-handed than usual and have to practice more with their right hand than their left to gain the same proficiency.³

Those who are converted left-handers—like my father—who were naturally left-handed but learned (or were forced) to write and do other tasks competently with their right hand, are often a confounding variable in studies on handedness.

There’s a huge literature on handedness with a lot of conflicting information and different methods of assessment, but overall, it appears that: handedness, in general, has a long evolutionary history and is not confined to humans; most people appear to be right-handed (perhaps as high as 90%) and this may have been true since Neanderthal times; anthropologists have proposed that the manipulation required for tool use during our evolutionary history may have provided a selection pressure for right-handedness but that the use of non-verbal communication (hand gestures) may have also contributed; of the 10% or so of the population that are left-handed, more are men than women, but these figures may be skewed by inconsistent testing methods; handedness develops over early childhood, usually settling in to right- or left-dominance by age six; control over handedness can be said to be both multi-genetic and developmental in nature because the various parts of the brain that influence handedness are not all in one place.⁴

Archeological data revealing prehistoric hand-use patterns for tool use and cave art have confirmed that right-handedness was already established in Neanderthals and that it may have emerged through the increasing frequency of complex, bimanually differentiated, tool-using activities. The observation in gorillas and chimpanzees of a significant right-handed asymmetry for actions toward inanimate targets, but not for actions toward animate ones, provides further support for the hypothesis that righthandedness has emerged from primitive manipulative activities.

…However, this ‘tool-use hypothesis’ does not account for the fact that handedness for tool use is not directly related to hemispheric dominance for language, since majority of left-handers do not exhibit a right-hemispheric dominance for language. [Cochet and Bryne 2013, pg. 536.]

Now to the big question: If most people are right-handed and a few left-handed, how do some people come to be mixed-handed? And what advantages and disadvantages are there to being mixed-handed?

It turns out you are more likely to be mixed-handed if you have a left-handed close relative (parent, sibling, or child), and to a lesser extent with extended family members (like a grandparent).

There may be an influence of slightly disrupted brain development during the third trimester of pregnancy or just after birth that skews toward more left-handed or mixed-handed children than expected, and which may affect for boys than girls. In a few studies, for example, more stress experienced by the mother during this time period (even just “more daily hassles”) was associated with more mixed-handedness in the children measured at age six. This study and others found a fairly strong signal for more mixed-handed and left-handed children among those born earlier-than-expected (before 37 weeks).⁵

Perhaps such a potential for disruption of brain development in late foetal life explains why there has been a strong tendency to associate mixed-handedness with various brain disorders—including autism, epilepsy, schizophrenia, dyslexia, ADHD, and intellectual disabilities.⁶

Such correlation studies are often not comparable or reproducible, in part because the definitions of what is meant by mixed-handedness differ so widely. However, these studies may also suffer from the same problem as the autism-as-a-vaccine-injury hypothesis I discussed in an earlier essay: that disruption of brain development in infants only happens during short periods of active growth that are individually-specific, which means not all babies that are exposed to a risk are actually affected.

In contrast, other research suggests that mixed-handedness is a benefit: that mixed-handed people exhibit more efficient communication and integration between their right and left brain hemispheres. As a consequence, the mixed-handed often have a greater awareness and understanding of their own thought processes (“metacognition”), and possess an increased ability to read music and play instruments that use both hands.

Researcher Elke Krause, who’s book Beyond Left and Right Handedness presents the most up-to-date and thorough analysis I’ve come across, seems to disagree with the Briggs and Nebes study discussed above. She concludes that overall, more left-handers than right-handers show evidence of mixed-handedness. And if mixed-handedness simply describes people who don’t consistently use one hand or the other, she states:

Considering that it is left handers (and not right handers) who show a very wide range of manual variability, it seems rather likely that a portion of so-called mixed handers are indeed left handers with a (very) mild degree who, in addition, may have switched handedness due to the right-biassed environment. [Krause (2023), pg. 97, my bold]

If Krause is right about this, it would mean that more than 10% of the population are left-handed, although some of these folks are simply not strongly left-handed.

In the case of my sister and I, given that our father was naturally left-handed, it may well be that my sister is indeed naturally—but not strongly—left-handed, and that as our mother suspected, she stubbornly insisted from an early age on learning to do most things with her right hand.

It’s also quite possible that the same could be said about me, but that my mother simply never noticed my left-handed tendencies, which is also entirely possible, under the circumstances of my early childhood I’ve written about before: by the time I was 19 months old, my mother’s attention was almost entirely focused on my critically-ill younger sister.

In fact, I may actually be more strongly left-handed than my older sister, that right-handed dealer of cards and walker of bicycles). It might also explain my one left-handed grandson, especially since neither of his parents are left-handed.

What we cannot be sure of is whether our mixed-handedness was due to our mother being exposed to an unusual amount of stress during the third trimester of both pregnancies. Did a slight disruption of brain development just before birth make us both less strongly left-handed? I don’t remember hearing that either my sister or I were born more than three weeks premature, but I could be wrong.

Alternatively, I do recall a story what might qualify as a late pregnancy stress for my mother just before I was born. I wrote a few months ago about my mother’s first husband—a young Danish sailor-turned-Norwegian-air force-navigator—who was killed in action during World War II. Years later, a monument was commissioned to commemorate all of the air men lost from the Norwegian Airforce squadron based at Sullom Voe in the Shetland Islands. Just before I was born in 1954, a letter apparently arrived inviting my mother to the installation ceremony in Norway.

I don’t know if the timing of this letter could explain my mixed-handedness, but it must have stirred up a lot of painful memories, and knowing she was unable to attend would certainly have been an added stress for my mother. It might have been that. Or, she might just have had more daily hassles in general during the last few weeks before both my sister and I were born. We’ll never know.

However, I do like knowing that my mixed-handedness connects me to my father through his left-handedness and similarly, ties my grandson to me.

I’d love to hear any stories you have of sudden mixed-handed awareness. Or am I more alone in this phenomenon than I imagine?

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1. Gutteling, B.M., de Weerth, C., and Buitelaar, J.K. (2007). Prenatal stress and mixed-handedness. Pediatric Research 62, 586-590. Open access. https://doi.org/10.1203/PDR.0b013e3181558678

2. Briggs, G.G. and Nebes, R.D. (1975). Patterns of hand preference in a student population. Cortex 11(3), 230-238). https://doi.org/10.1016/S0010-9452(75)80005-0

3. Krause, E. (2023). Beyond Left and Right Handedness. Springer Nature. https://doi.org/10.1007/978-3-031-24389-9 Request a pdf of the book here.

4. Cochet, H. and Byrne, R.W. (2013). Evolutionary origins of human handedness: evaluating contrasting hypotheses. Animal Cognition 16, 531–542. https://doi.org/10.1007/s10071-013-0626-y

Krause 2023, ref. 3

5. Guttling et al. 2007, ref. 1

Krause 2023, ref. 3

Obel, C., Hedegaard, M., Henriksen, T.B., et al. (2007). Psychological factors in pregnancy and mixed-handedness in the offspring. Developmental Medicine and Child Neurology 45(8), 557-561. Open access. https://doi.org/10.1111/j.1469-8749.2003.tb00956.x

6. Fritsche, S. A., & Lindell, A. K. (2019). On the other hand: The costs and benefits of left-handedness. Acta Neuropsychologica, 17, 69-86. file:///C:/Users/sjcro/Downloads/On_the_other_hand_the_costs_and_ben.pdf

Krause 2023, ref. 3

Orr, K.G.D., Cannon, M., Gilvarry, C.M., et al. (1999). Schizophrenic patients and their first-degree relatives show an excess of mixed-handedness. Schizophrenia Research 39(3), 167-176. https://doi.org/10.1016/S0920-9964(99)00071-7