Archive for October 15, 2014

Teaching Computer Science Better to get Better Results

This is my third blog post in a series inspired by a thread in the SIGCSE-Members list and by the Slate article which argued that “Practice doesn’t make perfect.” Macnamara et al did a meta-analysis of studies of expertise, and found that a relatively small percentage of variance in expertise can be explained through hours of practice. The Slate authors argue that this implies that genetics explains the rest of the variance.

  • In the first post (see here), I argued that the practice+genetics is too simple to explain expertise. First, practice can be deliberate, lazy, or teacher-led. Second, there is experience that leads to expertise which is between genetics and practice. The most significant flaw of both Macnamara et al. and Ericsson et al. is ignoring teaching.
  • In the second post (appearing yesterday in Blog@CACM), I addressed a claim in the SIGCSE-Members list that programmers are “wired” differently than others. Most CS teachers agree with the Slate authors, that students can NOT be more successful with more work. The evidence that better teaching leads to better learning is overwhelming. In fact, there is significant evidence that teaching can even overcome genetic/innate-ability differences.

Lots of CS teachers believe in the Geek Gene Hypothesis, and for good reason. It’s frustrating to have seemingly no impact on some, especially the lower-end, students. Even the award-winning Porter, Zingaro, and Lister paper points out that the earliest assessments in the class they studied correlate very highly with the final grade. Gas Station without Pumps voiced a similar sentiment in his blog post in response to the Slate article:

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.

I agree. It’s not really knowable where the difference comes from and it’s not really relevant. The point of my Blog@CACM post is: we can do better. If we can teach spatial ability and subitizing, two skills that have a much stronger claim to being innate than programming, then we can certainly teach people to program better.

If we follow common practice and it’s unsuccessful, it’s not surprising that we think, “I tried. I explained carefully. I gave interesting assignments. I gave good feedback. It’s got to be an innate trait. Some students are just born wired to program.

I watch my children taking CS classes, along with English, Chemistry, Physics, and Biology classes. In the CS classes, they code. In the other classes, they do on-line interactive exercises, they write papers, they use simulations, they solve problems by-hand. Back in CS, the only activity is coding with feedback. If we only have one technique for teaching, we shouldn’t be surprised if it doesn’t always work

Here’s a reasonable hypothesis: We get poor results because we use ineffective teaching methods. If we want to teach CS more effectively, we need to learn and develop better methods. If we don’t strive for better methods, we’re not going to get better results.

A first step is to be more methodical with how we choose methods. In a 2011 paper by Davide Fossati and me (see here), we found that CS teachers generally don’t use empirical evidence when making changes in how we teach. We act from our intuition, but our students aren’t like us, and our intuition is not a good indicator of what our students need.

Next, we need to experiment with more methods. We want to get to a place where we identify known problems in our students’ understanding, and then used well-supported methods that help students develop more robust understandings. We probably don’t have a wide range of different techniques for teaching assignment, iteration, recursion, and similar concepts? We should try well-supported techniques like pair programming, peer instruction, or Media Computation (see CACM article on these). We should try to expand our techniques repertoire beyond simply grinding at code. We could try techniques like worked examples, Problets, CodingBat, games with learning outcomes like Wu’s Castle, multiple choice questions like in Gidget, the Parson’s Problems in the Runestone Interactive ebooks, or even computing without computers as in CS Unplugged.

We do not make it easy for CS teachers to pick up new, better, more proven methods. Sure, there are the SIGCSE Symposium proceedings, but that’s not a systematic presentation of what to use when. This is on the CS education research community to do better. But it’s also on the CS teaching community to demand better, to seek out better methods and studies of techniques.

If we taught better, there are a lot of problems in CS that we might impact. We might bring in a more diverse group of students. We might make our current students more successful. We might change attitudes about computing. Perhaps most importantly, maybe we as teachers will come to believe that we can teach anyone to program.

October 15, 2014 at 8:32 am 35 comments


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