Side note: I obviously should have thought about how I looked before I taped myself. Right after this video, we headed to the Y (for obvious reasons - ha!), therefore I have a slicked back ponytail and no make-up. Don't hold my appearance against me . . . You will see that this is a "one shot" deal - once your child sees it, you really can't do it again, at least not for several months. Soooo . . . there was no retaking the video or it wouldn't be real. :)
This is a good "assessment" of sorts to see how your child is cognitively thinking. I remembered this little activity after Carolina "sorted" all my recycling all over the kitchen for me. What a helper! ha!
Here's what you need: two brown paper bags; two jars, one thin and tall (I used an empty spice jar), and one wider (I used a jelly jar I think); and marbles or some other like object. This is important: fill up the tall, thin jar with the objects and then DOUBLE the amount. You will understand once you watch the video. . .
Here's why you should do it: The technical term is "Conservation of Number" - If they are able to understand that the number is the same in spite of the visual differences once the jars are removed, then "conservation of number" has been mastered.
Here's how you do it: Place the jars in the bags without your child seeing the jars. (In their minds the jars are the same size and shape) The glass jars add a nice "clink" and interest to the activity. . .
Alright, so he got a little bored during the whole process, but then I did, too, making sure each marble went into the jar. :) He was confident that they were the same all along, but when I pulled them out, he wasn't so sure after all. (But I think he did question himself trying to decide.)
Notice I didn't tell him, "Of course they were the same because you said it the entire time", but I let him prove and discover on his own by counting that they were indeed the same. This is an important step because it solidifies in a concrete way what he saw and then believed once the jars were revealed.
Go through your recycling and try this out! :)