How do teachers teach recursion with embodiment, and why won’t students trace their programs: ICLS 2020 Preview

This coming week was supposed to be the International Conference of the Learning Sciences (ICLS) 2020 in Nashville (see conference website here). But like most conferences during the pandemic, the face-to-face meeting was cancelled (see announcement here). The on-line sessions are being announced on the ICLS2020 Twitter feed here.

I’m excited that two of my students had papers accepted at ICLS 2020. I haven’t published at ICLS since 2010. It’s nice to get back involved in the learning sciences community. Here’s a preview of their papers.

How do teachers teach recursion with embodiment

I’ve written here about Amber Solomon’s work on studying the role of space and embodiment in CS learning. This is an interesting question. We live in a physical world and think in terms of physical things, and we have to use that to understand the virtual, mostly invisible, mostly non-embodied world of computing. At ICER 2018, she used a taxonomy of gestures used in science learning to analyze the gestures she saw in a high school computer science classroom (see link here). Last summer at ITiCSE, she published a paper on how making CS visible in the classroom (through gesture and augmented reality) may reduce defensive climate (see link here). In her dissertation, she’s studying how teachers teach recursion and how learners learn recursion, with a focus on spatial symbol systems.

Her paper at ICLS 2020 is the first of these studies: Embodied Representations in Computing Education: How Gesture,Embodied Language, and Tool Use Support Teaching Recursion. She watched hours of video of teachers teaching recursion, and did a deep dive on two of them.

I’m fascinated by Amber’s findings. Looking at what teachers say and gesture about recursion from the perspective of physical embodiment, I’m amazed that students ever learn computer science. There are so many metaphors and assumptions that we make. One of the teachers says, when explaining a recursive function:

“Then it says “… “now I have to call.”

Let’s think about this from the perspective of the physical world (which is where we all start when trying to understand computing):

• What does it mean for a function to “say” something?
• The function “says” things, but I “call”? Who is the agent in this explanation, the function or me? It’s really the computer with the agency, but that doesn’t get referenced at all.
• Recursion is typically explained as a function calling itself. We typically “call” something that is physically distant from us. If a function is re-invoking itself, why does it have to “call” as if at a distance?

For most computer scientists, this may seem like explaining that the sky is blue or that gravel exists. It’s obvious what all of this means, isn’t it? It is to us, but we had to learn it. Maybe not everyone does. Remember how very few students take or succeed at computer science (for example, see this blog post), and what enormously high failure and drop-out rates we have in CS. Maybe only the students who pick up on these metaphors are the ones succeeding?

Why won’t students trace their programs?

Katie Cunningham’s first publication as a PhD student was her replication and extension of the Leeds Working group study, showing that students who trace program code successfully line-by-line are able to answer more accurately questions about the code (see blog post here). But one of her surprising results was that students who start tracing and give up do worse on prediction questions than those students who never traced at all. In her ITICSE 2019 paper (see post here), she got the chance to ask those students who stopped tracing why they did. She was extending that with a think-aloud protocol, when something unusual happened. Two data science students, who were successful at programming, frankly refused to trace code.

Her paper “I’m not a computer”: How identity informs value and expectancy during a programming activity is an exploration of why students would flat out refuse to trace code — and yet successfully program. She uses Eccle’s Expectancy Value Theory (which comes up pretty often in our thinking, see this blog post) to describe why the cost of tracing outweighs the utility for these students, which is defined in terms of their sense of identity — what they see themselves doing in the future. Sure, there will be some programs that they won’t be able to debug or understand because they won’t trace line-by-line. But maybe they’ll never actually have to deal with code that complex. Is this so bad?

Katie’s live session is 2:00-2:40pm Eastern time on June 23. The video link will be available on the conference website to registered attendees. A pre-print version of her paper is available here.

Both of these papers give us new insight into the unexpected consequences of how we teach computing. We currently expect students to figure out how their teachers are relating physical space and computation, through metaphors that we don’t typically explain. We currently teach computing expecting students to be able to trace code line-by-line, though some students will not do it (and maybe don’t really need to). If we want to grow who can succeed at computing education, we need to think through who might be struggling with how we’re teaching now, and how we might do better.