Reasoning with Which One Doesn't Belong

I do a 15-minute Which One Doesn't Belong session most weeks. I've blogged about WODB before, and I regularly tweet about it. Last year my Grade 3s were getting really expert. This year, my K3 (5,6 year olds) are all really into them.

Over Christmas my copies of Christopher Danielson's book and teacher's guide arrived. I've been enjoying the teacher's guide; there's a lot of background in there, and a lot of useful advice. I really recommend it. Christopher took the book through its paces with children of  all different ages, and despite the simplicity of the basic idea, there's a lot to think about in its execution.

Christopher looks at development as a geometer using the Van Hiele model:

A lot of my students' thinking is, not surprisingly, at Level 0. But there's also a fair bit of Level 1 emerging. And at Level 1 with WODB you start to get some great reasoning.

Today I used this one that I'd made:

All but one of the 22 students had at least one thing to say:

Christopher suggests using this kind of recording as a reminder, and spur to further thought:

"Simply writing a key word (square) or phrase (all angles the same) or sketching a quick diagram, or circling key features of the shape are all quick ways to maintain visible reminders of the unfolding conversation for everyone to access." (p30)

And it's making me think that I should keep these up, because there's a lot of things that need returning to and developing, and who knows at what pace and at what moment thoughts will come to people?

I made some low-res video of the session. Here's a few moments. In this one you can see one of the "it's like" observations, and also one that describes a property (the red one is the only one with one round bit).

Some of the "it's like" statements need further investigation:

Sometimes an observation of a property leads to a discussion about what exactly that property is, the sort of reasoning I really want to develop in my students:

So maybe we need to pin up that second sketch too, and come back to it?

Tweeting about moving from "it's like" to properties, I got some good advice from Christopher and from David Butler:

@Trianglemancsd @Simon_Gregg Would a question like "what is it that makes it like a clam?" help to make the move?

— David Butler (@DavidKButlerUoA) January 12, 2017

We also talked about when to introduce vocabulary. I'd be interested in ideas about how to develop this. How could this kind of lesson be extended in another lesson, maybe in smaller groups or individually? What, in all this is worth developing? What I think would really help my class is to  encourage everyone somehow to look for properties and reason about them. Ideas?