Gas station without pumps

2014 October 13

Practice, teaching, or genetics

Filed under: Uncategorized — gasstationwithoutpumps @ 10:04
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Mark Guzdial, in The 10K Hour Rule: Deliberate Practice leads to Expertise, and Teaching can trump Genetics | Computing Education Blog, responds to a Slate article claiming that genetics is more important than practice:

Here’s my argument summarized. The Slate authors and Macnamara et al. dismiss the 10K hour rule too lightly, and their explanation of genetic/innate basis for expertise is too simple. Practice is not the same as deliberate practice, or practice with a teacher. Expertise is learned, and we start learning at birth with expertise developing sometimes in ways not directly connected to the later activity. The important part is that we are able to learn to overcome some genetic/innate disparities with good teaching. We shouldn’t be giving up on developing expertise because we don’t have the genes. We should be thinking about how we can teach in order to develop expertise.

Mark’s blog is read (or at least commented on) mainly by teachers of computer science, so he is largely preaching to the choir here. I would like to believe that my teaching makes a difference—I spend almost all my time teaching, grading, or preparing to teach.

I do believe that most students in my classes leave the class with better skills than they came in with.  Whether that is due to my teaching or just to the students being forced to practice is somewhat difficult to determine—to a large extent my teaching style consists of forcing students to practice skills that they’ve generally ignored in the past (like in-program documentation) and providing them detailed feedback on their practice.  I’d like to believe that the feedback (both individual and group) matters, since I give up my weekends to provide the feedback.  If only the practice matters, then I could do as many of my colleagues do and just do I/O testing or delegate the feedback to untrained undergraduate graders.

So I have a bias towards believing Mark’s claim that teaching matters, and that there is a difference between different sorts of practice by students.

But the outcomes for individual students seem to depend more on the students coming in than on what I do.  Those students who come in better prepared or “innately” smarter progress faster than those who come in behind, so the end result of the teaching is that differences among the students are amplified, not reduced. Whether the differences in the students coming in are due to prior practice, prior teaching, or genetics is not really knowable, but also not really relevant.

Mark claims that “Genetics/innate starts at birth, no later”, which is somewhat of a simplification.  Although innate differences are present at birth (by definition), they may not be expressed until much later, either due to the developmental program that coordinates gene expression or due to environmental triggers.  So phenotypic differences may not appear until much later (genes for patterns of facial hair among men generally make no difference until puberty, for example).

He claims that

If you’re going to make the genetics/innate argument, you have to start tracking participants at birth. Otherwise, there’s an awful lot that might add to expertise that’s not going to get counted in any practice logs.

I’ve only had one child that I have taught from birth on (and lots of others also taught him), and we all know the uselessness of sample size=1, so it is not possible for me (and probably for anyone) to track participants from birth for a significant sample size.  But there are certainly ways to estimate the heritability of talent without tracking all activity since birth—the twin studies that he dismisses attempt to do precisely that.  (Some of the twin studies are well done and some are useless anecdotal reports—but there is substantial evidence that some talents have a substantial heritable component.)

Of course, it is always hard to pick apart whether “nature” or “nurture” is responsible for a particular difference in talents, since there is a large feedback loop.  Small differences in initial results can result in differences in how much pleasure practice provides and how much support is given, which can in turn affect how much practice is done and how valuable the practice is.  So small differences in “innate” talent can be amplified to large differences in outcomes.

I’d like to believe Mark’s claim that “Hours spent in practice with a good teacher are going to contribute more to expertise than hours spent without a teacher,” and that I’m a good enough teacher to make that difference.  But I fear that there is a lot of confirmation bias here—I want to believe that what I do matters, so I accept articles and studies that confirm that belief.

Looking back over my own education, I had a few teachers who helped me progress, and a few who probably delayed my learning by convincing me that the subject they were teaching was unutterably tedious, but a lot of my learning was on my own without a teacher. Sometimes the initial learning was with a teacher (often my Dad, when I was child, see Thanks, Dad), but subsequent learning was pretty much entirely from books and solo practice.  It is hard to say whether I would have achieved more expertise with teachers—some of the stuff I learned was esoteric enough that there were no teachers and I had to teach myself.  Other material was more commonly available, but I came at it from an unusual direction, so that the conventional ways of teaching the material would have been a very bad match for me.

Having an expert mentor around can make difference, and structured practice (such as I assign to my students) can make a difference—even just having an externally imposed reading schedule can make a difference.  But most of my learning in the past couple of decades has been without a teacher and without an externally imposed course structure.

So my own experience is that teachers are not the secret sauce to developing expertise.  Good teaching helps, but good learning can take place even in the absence of teachers.

Mark wrote

Look back at that definition of “deliberate practice”—who’s going to pick the activities that most address your needs or provide the immediate feedback? The definition of deliberate practice almost assumes that there’s going to be teacher in the loop.

I think Mark is wrong here.  For example, when I was teaching myself electronics design, I picked the activities based on what I wanted to design.  The feedback came from building and testing the circuits—from the real world, not from the opinions of teachers. I found that some of the simplified models used in the text books and religiously repeated in intro courses were not very useful, while others were very handy and gave good results.  Having a teacher steering me would have probably resulted in less learning, because I would not have been as invested in the examples (so less willing to explore) and the examples would have been chosen to give the conventional results, rather than showing where the conventional models break down.

For example, my post Capacitance depends on DC bias in ceramic capacitors explains how I found out about how ceramic capacitors change their capacitance with DC bias.  The knowledge was out there in various industrial application notes, but it is not generally taught in beginning electronics courses—capacitors are treated as ideal devices.  A teacher would probably have led me to a circuit that did not have a large DC bias on the capacitors, so that they would have acted much like the ideal devices, and I would not have learned a very important (and often overlooked) flaw in the models.  I may be less expert in the conventional models than someone who spent the same amount of time studying electronics with a teacher, but I have picked up odd bits of learning that I would have missed with most teachers.

Similarly, my posts Diode-connected nFET characteristics, More mess in the FET modeling lab, and Mic modeling rethought showed my learning about the characteristics of nFET transistors, where I ended up with a different model from the textbook ones.  Teachers would have almost certainly directed me to learn the conventional model first, and then much more complicated models to patch the conventional model (that’s all I could find in any of the textbooks).  Not having a teacher let me find a useful simple model for the I-vs-V curve that models the entire curve fairly well, without having to switch between models.  (Incidentally, I never did come up with an explanation for the negative resistance in the first nFETs measured in the “more mess” post—that part has been discontinued and other nFETs I’ve measured don’t exhibit the phenomenon.)

Mark might argue that I had good teachers in the past, which allowed me to develop more expertise at self-teaching.  I won’t dispute that, but I think his main point “the definition of deliberate practice almost assumes that there’s going to be teacher in the loop” is refuted by self-teaching with real-world feedback.


  1. Nice analysis — thanks! I see your point. I think I’d restate that sentence as ““the definition of deliberate practice almost assumes that there’s going to be teacher in the loop FOR MOST PEOPLE.” Given who you are, you’re capable of learning with self-teaching and real-world feedback. Most people do not do that successfully. Most people are not auto-didacts. There’s also the issue of *efficiency*. I do believe that I can teach programming far more efficiently than can learners on their own. They will learn more and faster working with a good teacher than they will on their own.

    Comment by Mark Guzdial — 2014 October 13 @ 10:13 | Reply

    • BTW, the next two posts (I’ve got a three part series here) will point out that I’m not preaching to the choir. Overwhelmingly, CS teachers do not believe that more effort leads to greater success — far more than CS students and far more than teachers in other subjects. See for example.

      Comment by Mark Guzdial — 2014 October 13 @ 10:26 | Reply

      • I note in that paper that faculty generally (more than 75%) rejected the statement “14. I cannot learn computer science without a teacher to explain it.” That seems to indicate your belief in the primacy of teaching is a minority position. Of course, there is a big overlap possible between rejecting “cannot learn” and believing that teaching helps, and I suspect we both fall into that overlap.

        You were highlighting item 4: “Nearly everyone is capable of succeeding in the computer science curriculum if they work at it,” which the faculty strongly rejected, but students weakly accepted. Given the high failure rates among the students who are already selected for top academic performance, I’m not convinced that “working at it” would be sufficient to get the bottom quintile of the population (who do not even finish high school) to succeed in the CS curriculum. I think that a weaker statement (like “the majority of university students”) would have gotten more faculty approval. The problem is what set you are quantifying over, and the professors may have a larger set in mind than the students (who may be misreading the question as “nearly everyone”=”you and your friends”). It could also be the tension between hope and experience. Dweck doesn’t promise that nearly everyone can do difficult things, just that people can get better if they adopt the attitude that they are capable of improvement. In short, item 4 does not ask a reasonable question that gets at mindset, but only at ignorance of the wide range of the population.

        Comment by gasstationwithoutpumps — 2014 October 13 @ 15:18 | Reply

    • I believe that my students learn more and faster with my teaching than they would without it. If I didn’t believe that, I’d give up teaching. But the home-schooling community is certainly questioning your belief that most people are incapable of self-teaching. Indeed, I think that many school curricula and teaching styles are crippling students’ ability to be autodidacts, and that part of our job as university professors is to try to repair that damage.

      I cringe when I see over-scaffolded courses at the university level, which turn students into note-taking, answer-memorizing automata, instead of encouraging to explore and learn stuff from a variety of sources. Computer science particularly lends itself to experimentation (low cost and low risk), but I see very little in most early CS courses.

      Comment by gasstationwithoutpumps — 2014 October 13 @ 15:24 | Reply

      • Strongly agreed: Computer science pedagogy should emphasize more experimentation. My suspicion is that the desire to teach “Good engineering practice” leads to an over-emphasis on up-front design, and a de-emphasis on exploring.

        You may be right that more students can be autodidacts. The constructionists would certainly agree with you. There are too few students being homeschooled today (3%, and mostly higher-SES) to test the hypothesis that way. I like to think about trying to support a wide range with different methods, e.g., things like meetups and maker-labs for the high-motivated, things like our workbook-like ebooks for the low-motivated.

        Comment by Mark Guzdial — 2014 October 13 @ 16:36 | Reply

  2. […] correlate very highly with the final grade. Gas Station without Pumps voiced a similar sentiment in his blog post in response to the Slate […]

    Pingback by Teaching Computer Science Better to get Better Results | Computing Education Blog — 2014 October 15 @ 05:32 | Reply

  3. […] correlate very highly with the final grade. Gas Station without Pumps voiced a similar sentiment in his blog post in response to theSlate […]

    Pingback by Marcos d'Ornellas' Portal | Teaching Computer Science Better to Get Better Results — 2015 May 31 @ 12:23 | Reply

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