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November 23, 2010 / Ben Chun

It’s all in how you ask…

I’ve been thinking a lot lately about how much we rely on common cultural context (at minimum, some kind of common language) in order to communicate in the classroom. Our greatest challenge as teachers might be just to understand our students and make ourselves understood. This is not because the subjects we teach are so complex, but rather because our backgrounds and ways of thinking can be so different.

An example of this came up today. My AP class has started looking at the GridWorld Case Study, a code base that they’ll learn for the exam. I think this is a great way to test more than syntax and algorithms, without requiring students to ingest complex multi-class systems during the exam. I use the College Board materials because I think the explanations are clear, and they provide good sets of questions and exercises that go through the case study code.

My students ran GridWorld for the first time in class last week, and I assigned the first set of questions for homework over the weekend. The very first question asks, “Does the bug always move to a new location? Explain.” To me, it seems clear that they want you to say, “No, the bug will move to a new location unless the location directly in front of it is blocked or nonexistent, in which case it will turn 45 degrees clockwise instead.”

But now look at these student answers and tell me they’re unreasonable:

“The bug is not always stationary, but the movement bug tends to be repetitive. So I wouldn’t consider the location to be new.”

“No, the bug doesn’t always move new locations, it follows its path again and again.”

“The bug only moves to a new location if the step or run button is on. If it is on the bug will move, and will turn when it reaches an obstacle. If no obstacles are in the bugs way, it would go in a circle forever.”

I think these are all great answers. We haven’t given strict definitions of our terms. And, as anyone who has written an exam knows, it’s hard to write questions that get exactly at a particular concept! We really have to work to avoid playing “Guess what the teacher is thinking”. I like that the College Board questions start with some black-box observation of the system. A lot of questions seem simple, but taken at face value are really just a starting point for deeper investigation.

Another example: “Can more than one actor (bug, flower, rock) be in the same location in the grid at the same time?” Well, if we just watch a bug move, we might not be able to tell if it removes and replaces a flower as it passes, or if it exists in the same location as the flower and has the side-effect of renewing the flower’s color. Similarly, if we right-click on an actor and find that, unlike a blank location, it offers a menu of methods to call but no options to construct new actors, we might not be sure if this is a limitation of the user interface or if it reflects something deeper about the system.

It’s important that we not treat differing answers here as wrong, and that we not toss off the questions as being trivial or as an excuse to just tell students how things work. They need to explore the depth of these questions themselves. The ways in which our language is imprecise are the exact ways in which we need to work to clarify our understanding of how a system works — and clarify what we are really asking!


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