The extremely brief history of handedness and neuroscience

I was hassled by an emeritus professor at a get-together over handedness, aka whether you are left-handed or right-handed (you can read some of the important parts of the conversation at the very end). He listed a myriad of reasons why "discriminating" against handedness was not appropriate for generalizing to the public and unethical.

After about 30 minutes of explaining my methods and the theory behind handedness, I came to realize two things: 1) there was no changing this man's mind -- I simply was not a good scientist in his eyes and 2) I didn't know much about the history of handedness other than the standard lines I tell people when we ask about handedness.

What is handedness -- other than... you know... the obvious stuff?

Handedness can affect lateralization, or what side of our brain is specific for certain functions. For example, our language areas of the brain are majority located on the left side of our brain... if you're right handed. If you are left handed (or ambidextrous), you have a greater likelihood of being right-brain dominant for language areas.

On top of handedness + lateralization research in language studies, memory functions have differences in terms of brain lateralization for lefties versus righties. Handedness also affects motor movement, the way your hair swirls, and your chances of getting breast cancer -- among other things. Even people who were forced to be right handed when they were once left handed show differences in lateralization.

There is even a textbook on handedness and neuroscience. Literally could be taught as a class.

Clearly, handedness has a lot more to it than what hand you open a jar with.

The discriminatory history on lefties

The first instance I can recall of lefty hate was on The Simpsons. Ned Flanders is left handed and even has a fairly involved episode tackling the issue of left handed discrimination -- something I thought was an absurd joke. You can check out a 60 second review of the episode below!

Left handed hate is much like any hate: ancient history followed by myth and myth-related fear. Even the word "left" itself was derived from the word lyft, which means "weak". Also, "awkward" and "sinister". Biblical reference states people who are on the "left" are damned.

Supposedly, left handed people were beaten until they were right handed in the 18th and 19th century -- no source was found on specifics of this particular aspect of the 18th and 19th centuries. However, it is culturally known in present-day that doing things with your left hand -- like eating or hand gestures -- can be considered disrespectful or rude or even unsanitary.

Education has been skewed to right handed learners -- there is generally a lack of left handed desks and left handed scissors in classrooms. Music instruments are also skewed towards right handed people -- even though the act of some instruments are seemingly involved with both hands (like guitar) -- where left handed instruments generally cost more money than right handed instruments. Left handed machinery (power tools, etc) were the first things I found out are majorly right handed (from that Simpsons episode!) and cost more than right handed tools.

Left handed neuroscience discrimination?

Is it unethical to discriminate against lefties? Human neuroscience does it all the time. In fact, many reviewers for human neuroscience journals usually ask how studies implemented handedness screening -- usually done by the Edinburgh Handedness Inventory (take it here!) -- and will ask you to screen your participants to verify your results aren't due to some other variable. In science, not being able to account for a possible variable is called a "confound" or a "confounding variable".

Confounds make science on human participants very hard. Unless people are doing an experiment in very controlled laboratory conditions, it's hard to say you are "controlling for all variables" (controlling for confounds) -- and even then, some variables (like age, sex, handedness, etc) need to be accounted for before the experiment begins. You wouldn't want to find some amazing result but have it refuted because your participants were lefties, or all men, or all 18, or any confounding variable that you may not have accounted for.

To control for confounds, screening participants so they "fit" into your study is important. You are looking to test a handful of participants that represent the demographics of the majority of the population -- left-handed people only make up 10% of the population.

Ideally, you would have 1 out of every 10 participants be left handed -- but not all left handed participants who say they will participate actually show up. Also, depending on what you're studying, there could be no handedness effect. Waiting for lefties in your study may be just a non-factor in your results.

However, to the credit of the emeritus professor who said my studies were pointless without lefties, there is actually a call for scientists to include the "often-discarded group" of left handed people into our data collection. This call is coming within the same year the NIH is calling for grant proposals that include both male and female animal models -- like handedness in human research, the majority of animal research is conducted on male animals only. Discrimination in participant population is being pointed out, regardless of your controlled environments.

Inclusion of lefties in research

Emeritus professor who crossed his arms the entire time I tried to explain my experiment said very plainly I would just collect all my data then sort out my data by demographics and see what "shakes out".

Well, that would work if I wanted to spend the next handful of participant money on the possibility that my data includes confounded results I could have accounted for.

Some of the difficulties in lefty inclusion involve funding. Of course, the ideal random sample would include any person who came through the door until an accurate demographic sample was collected -- including people who are lefties, who are disabled, who are veterans, who are in the highest socioeconomic status, who are vegans, etc. But that is not possible for tons of reasons, but a few stick out in my mind: 1) the questionnaire required to accurately assess every dimension of population demographics would be so large that it could take some hours to answer, 2) the IRB probably wouldn't approve all the items in this questionnaire, 3) even if IRB approved it, you couldn't force people to answer every question, which leads to 4) if people are excluded from your study because of your ultra-demographics questionnaire, you still have to pay them for their time in your lab -- even though you wouldn't use their data! With limited funding, this approach is simply not feasible.

It is a good move to be more inclusive in your research, but I don't believe left handed inclusion needs to occur in one fell swoop in every study. Testing a traditional right-handed, typically developing population gives way to many different questions you can test -- not just left-handed, but atypical populations, different ages, different socioeconomical statuses, etc. If you are interested in a left-handed population, your contrast group (righties) are already there.

Many people ask (or rather, say to me rhetorically): if two populations behave the same way, why do I care about the neural activities? Well, for lefties, it's not a question I'm personally interested in. But in the face of inclusiveness, it isn't something hard to implement. And the exclusion of 10% of the world is still a fairly large number (>700 million people). In contrast, if all the lefties in the world were a country, it would be the third largest country by population (China and India being 1 and 2, respectively; USA theoretically being 4th).

Greater inclusion can lead to updated neural models we knew specifically for righties; in my focus, decision making has been considered without laterality, but that's because there has been no behavioral reason to research lefties. We simply don't know the difference between lefties and righties in terms of many decision making questions. Creating better, more accurate models for how people choose is a direction of my research I would like to support. But currently, I'm far off from testing for left handedness, laterality, or behavioral anomaly. Maybe someone else would choose to do pursue this sort of research?

Emeritus professor epilogue

The purpose of this post was really to further educate me on a norm in neuroimaging beyond the concept of "eliminating confounding factors". The handful of different articles I read on laterality and handedness led me to believe handedness actually elicits brain activations I had no idea could be lateralized differently (like memory formation -- whaaaaat). This led me to questioning my own research. But many reports showed no behavioral differences, but differences in brain area/pathway usage. In my studies, I weigh slightly more heavily on behavior with supporting evidence from a neural activity stand point, so handedness and lateralization of activities/pathways are factors I am personally not interested in currently.

Another reason was to vent over how this holier-than-thou guy wanted to run up on my dissertation. You don't tell the baker how to make bread, do you?

When I asked him, "Well, why don't I just do it the way it has been done for decades and then test against different populations like how my proposal is laid ou--"


Just because that's how it's done doesn't mean it's right.

That's true, Mr. "you are wrong, but I'm telling you in cliches". Apparently, my concept of "baseline" is incorrect and that there is only one way to be more inclusive. I mean, who am I to question someone who has never done neuroscience research before?

The IRB won't let you discriminate --

Apparently, I am a discriminator now

-- against people who are left handed. What would they think?

Well, they approved the inventories I used to screen people. I guess they don't think much about it at all.

"Well, animal models have been tested on majority male animals. Are those animal researchers sexist?"

*waves hand in my face* I don't know if your committee will approve something like this.

Yeah, not many committees approve traditional methods of experimentation. Also, "talk to the hand" technique? That's like the subtweet of the 90s.

Maybe you should rethink your timeline here.

Good advice, buddy. Whenever you need advice about anything from an unqualified douche bag, give me a call and I'll return the favor.

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