Walter Lewin, the art of teaching, and physics’ gender problem

Physics and its gender gap are back in the public eye again, after news that Walter Lewin, a beloved physics professor at MIT, had been sexually harassing some of his female students. I was hit particularly hard by this news; I was a physics major at MIT a few years ago, and I know there is at least one course I wouldn’t have passed without Lewin’s excellent OCW videos. Taking those videos and courses down was absolutely the right course of action for MIT, and I applaud my alma mater for reacting quickly and firmly.

The news got me thinking about the gender gap in physics and the culture that makes it possible. Many people have already outlined many reasons for it: discrimination in hiring, salaries, and resources, socialization at an early age, and so forth. I want to delve into a possible factor that I’ve never seen mentioned before, but that I suspect is partially responsible for the gap. It’s one that’s particularly connected with Walter Lewin: teaching.


Physics classes are traditionally separated into two parts: lecture and recitation. Lecture is where you learn the concepts, like F=ma. Recitation is where you’re supposed to learn to apply those concepts to problems, like using F=ma to calculate the trajectory of a projectile. In practice, what happens in recitations is that professors will restate the concepts (“As you learned in lecture, F=ma”), give some very basic hints on the problems (“When doing problem 6, keep in mind that the given angle is not the usual angle given in these problems”), and maybe will do a couple of basic example problems out of the book. What they won’t do, even if asked, is teach students methods for solving the types of problems that have been assigned to them. I’m serious — physics professors literally refuse to teach students the skills they need to succeed in physics (or, at least, in physics classes). This isn’t an oversight. It’s felt that struggling with problem-solving, having to discover every technique for every problem on your own, forces better understanding of the material, builds character, and that it would just be a shame to deprive students of the amazing feeling you get when you suddenly realize how to do a problem after hours of struggling with it.

I strongly disagree with this philosophy, and here’s why. A physics grad student I know, in defending this method, said something along the lines of, “Well, it’s like programming. Programming is a really hard skill to learn. You just have to struggle through all the pain in order to get to the point where you suddenly understand how to think programmatically. You can’t just hand that to someone.”

The thing is, I think you can. My experience of learning programming was very different from my friend’s. I didn’t find myself struggling much in my introductory programming class in college. (Well, I did just slightly above average on the tests — having the immediate feedback of seeing whether or not a program would run turned out to be key to my early programming skills — but I got very high grades on all of my programming assignments and projects without having to spend an inordinate amount of time on them.)

This was due solely to my excellent TA. When a concept like recursion was introduced, he didn’t just tell us the definition and then expect us to go home and spend several hours figuring out how to generate the Fibonacci sequence recursively. Instead, he worked on our problem-solving skills. First, he gave us examples of many different recursive functions, and walked us through how each one worked. Then he handed us several different types of problems and had us work through both recursive and iterative solutions to each — with him there, so he could help us when we got stuck. Then he gave us some medium-hard functions to solve recursively, and gave us feedback on what we did wrong, and showed us the right answer when we needed it. After that, doing my assignment was easy, because I’d been given a thorough grounding in the actual skills of breaking down a problem into a recursive function. (And I was no less happy when I solved a difficult problem.)

Some people say that spoon-feeding students material like this makes them worse at solving problems by themselves. Again, my experience has been exactly the opposite. After a semester of being taught programming step-by-step, I became a pretty decent programmer. In fact, I’m currently employed as a data scientist, so I now essentially write code for a living. And I’m good at it. I write the vast majority of the non-SQL code my team uses. I’ve looked at engineers’ screens and immediately found the bug in their code, even in languages I don’t know. This isn’t just because of practice — it’s also because I was explicitly taught how to break a problem down and think about it programmatically. It’s because someone really tried their best to hand me the experience of learning how to program. I put it like this:

Being explicitly taught programmatic thinking didn’t make me a bad programmer. It made it easier for me to be a good programmer.

I want to emphasize that this teaching method did not involve dumbing down assignments or tests, or giving students the answers to their assigned problems. It was about modeling and teaching problem-solving skills to create a foundation that students could build on in their assignments and tests. My grade was still based on how well I was able to deploy those skills in various circumstances, and how well I was able to think critically about them to figure out new ways of approaching problems. The difference was that someone was trying to actually teach these skills to me, rather than treating them as completely mysterious ideas that were only understandable after hours of internal struggle. Which isn’t to say that the internal struggle doesn’t help, or that hard work shouldn’t be rewarded. I’m just not convinced it’s as necessary as people make it out to be.

On the other hand, what do I know? I’m one of those women who leaked through the pipeline. I never went to grad school, and I don’t have firsthand knowledge of what it takes to succeed in academic physics. Maybe not being able to figure out everything without being taught really is a sign that a student isn’t cut out for the big leagues. I honestly don’t know. In fact, I suspect that no one knows this for sure.

It’s already well-known that large research universities generally don’t prioritize the teaching skills of their faculty. Universities want money, money comes from grants, grants come from research, and research comes from time — time that can’t be spent preparing for classes or figuring out a better way to teach a subject. Despite this, many professors do genuinely care about their students and sincerely want to do the best they can at teaching them.

But even these professors are the ones who’ve made it through a system that, at worst, considers the teaching of problem-solving skills to be cheating. At best, they’re just not aware it’s an option. I distinctly recall my freshman roommate telling me about her troubles with solving problems in a math class. She went to her TA, who told her, “Look, some people just have problem-solving ability, and some don’t.” Taken aback, she responded, “But isn’t that something you could teach? Like, couldn’t you explain to me how to do this kind of problem?” The TA’s reaction? “Oh…I guess…maybe… maybe we could teach problem-solving skills! I never thought of that before!”

The people who do really well in these classes are, like this hapless TA, the ones who don’t have to be taught these skills. It never occurs to them that something is missing from the traditional method of physics instruction, because, for them, nothing was missing. Why is this? Well, much of it is sheer grit — people work very, very hard to figure these skills out for themselves. Some of it is also about their willingness to approach professors and ask for help. Some of it is about outside help, because people come in with different levels of preparation, or because they have more outside resources to draw on (either financial or having easier access to expertise).

Whatever it is, I believe this is why many physics professors and grad students think of problem-solving skills as unteachable. After all, no one explicitly taught them, and they figured it out just fine. In fact, figuring it out was the best part! And every year, enough students like them come into the system to validate the idea that these skills don’t really need to be, and shouldn’t be, taught.


I think this system, and physicists’ blindness to it, is harmful in several ways. For one thing, it ignores that some students simply may not have the necessary problem-solving preparation to be able to grit their way through physics. Even hours and hours of hard work in isolation may not help a student who doesn’t quite understand how to approach problems analytically in the first place. (The usual response to this is that students aren’t supposed to work on these problems themselves, but are supposed to work in groups — essentially, that students are supposed to teach each other these skills. It’s unclear how this is supposed to help someone who can’t find a group whose schedule works with theirs, or what happens when other students working on the problems quite understandably aren’t equipped to teach their peers.) So a student who simply needs more help, or needs to be taught slightly differently to reach the same a-ha, is often told that they just haven’t worked hard enough. This is what led one of my introductory physics professors to tell us, “Well, the average for you guys on this test was 40%, but someone did get a 100%, so obviously we taught all of you what you needed to know and most of you didn’t work hard enough.” A friend of mine had a similar anecdote, where her introductory physics professor often refused to help her study group during office hours because he felt that if they didn’t understand the material, they simply weren’t working hard enough.

Some professors take this to even more of an extreme and decide that success in physics is simply predestined. This is what led one physics professor my friend had at Caltech to declare to his class that “education is a mining operation to figure out which students are worth educating.” It’s what led a professor talking to a grad student friend of mine to tell him, “Well, on this problem, the stupid students don’t realize that they need to take this effect into account, but the smart ones do, so that’s how I know the test is working.” People who are put off by these sentiments don’t become physics professors. So many physicists are able to look at the result of the system they’ve created and decide that it’s not about the system, but about innate ability, especially the same innate ability that they have — which means there’s no reason to even try getting anyone else up to speed.

I suspect, though I cannot prove, that as soon as you decide that performance in your field is due mostly to some kind of innate ability, you stop respecting diversity in many ways. You stop respecting diversity of thought, because you’ve just picked one learning style and decided that it’s the only one worth teaching to. And I suspect — although, again, I cannot prove — that you stop respecting diversity of gender or race. After all, if success is all about some kind of innate ability, then there must be some reason why everyone who exhibits it looks the same.

Now, I don’t think this is conscious on many people’s part (although many different people have told me stories about male physics professors at MIT complaining that women and minorities are bringing the quality of their students down, or making other similarly overtly sexist and racist statements). Again, many professors genuinely care about teaching their students, all of their students. They’re aware that systemic historical discrimination has played a very large role in determining who has had success in STEM fields, and they realize how problematic the above sentiments are. But they still don’t have the time to sit down and deconstruct everything about how they were taught physics and figure out a new way of teaching, so they go with what they know and what they feel worked. And I think they’re often not aware that this teaching style — the style that everyone uses, the style that everyone defends as the best — seems designed to privilege the students who come in with the best problem-solving preparation due to socialization or socioeconomic background, the students who are most comfortable interrupting class or seeking out professors to ask questions, the students who are most likely to buy into the idea that much of physics is unteachable because they’re the most likely to be confident in their abilities: white men.

Or, to put it another way: 40% of American students planning to major in STEM fields quit in college, because they find it too difficult — a state of affairs that is intentionally cultivated in physics. And women, already aware that they’re the minority among their teachers and peers, are more easily discouraged even when they’ve put in the necessary work and are well-regarded by their professors. (I particularly liked this NYT piece that mentioned this.) It seems logical to speculate that perhaps women and minorities are the ones who are most likely to be put off by the way physics is taught. In this context, physics teaching almost functions as a subconscious gatekeeping mechanism: if we deliberately do this, if we make it as difficult as possible for students to gain the skills they need for success in our classes, it’ll make it easier on us later by getting the people who don’t deserve to be here with us to quit.

(This is a good place to emphasize that I don’t think everyone does have what it takes to be a great physicist. I’m just wondering if there are people who do have it, but who are excluded early on by physicists’ insistence on making students figure out everything on their own.)


To tie this back to Walter Lewin: one reason I was so upset to hear about this situation is because I considered his lectures one of the very best ways to convince people that physics really is understandable and that it does ultimately make sense. I’ve recommended his lectures to many women over the years. I can’t tell you what a sense of betrayal I felt upon learning about his actions, and my heart goes out to his victims.

Lewin, as an emeritus professor, was one of the very few people with the interest, time, and persistence to figure out how to teach physics well. His behavior demonstrates that even when this exists, it still exists in a problematic overall physics culture — one that enables people to behave as badly as they like as long as their work is good, and that selects for those people later. Again, I suspect but cannot prove that this is partially due to the way physics is taught: that once someone has bought into the mindset that pain and struggle are this necessary for development in their field, they start excusing all different kinds of bad behavior. An advisor is a jerk to their grad students? Well, it helps build character and pushes the student. A man behaves inappropriately towards his colleague? Well, that’s just part of how people learn not to do things like that, by struggling with something and making lots of mistakes before it all suddenly snaps into place. Before the recent news, I had felt that Lewin’s lectures, perhaps unintentionally, were one of the best ways to combat that culture, simply by making such a strong statement that physics actually could be quite accessible.

So when I read that MIT was taking his courses down, I was upset. His lectures are one of the very few examples of really good physics teaching that I have ever seen. I was upset even though I knew that removing those courses was very much the morally correct decision to make. And I’m still upset — that the state of physics teaching is so very dire that just banning one guy for harassing women (which was, again, the correct course of action) can end up completely eliminating one of the sole excellent resources for aspiring physicists. Because there should be lots of excellent resources. It shouldn’t matter that one professor’s work was taken down, because there should be many, many more to take his place. That there aren’t is, I believe, very much a systematic problem of how physics is taught. And I think it’s one that physicists shouldn’t hesitate to fix.

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