Passing a Test

The prize is under one object.

Your humble blogger used to enjoy solving puzzles. That pastime ended when marriage, full-time employment, and later, the Internet, provided more important and/or pleasurable diversions.

Concerned about my absent-mindedness as a precursor to something worse, an adult son played a YouTube clip of a puzzle similar to one used on the Oxford admission test.

The problem is straightforward.

Shilpa is told the shape of the object under which the prize is located, while Colin is told its color. Both participants know that fact about each other. Then the following dialogue ensues:

Host: Do either of you know where the prize is?
(Silence)
Host: Do you know now?
(Silence)
Host: Do you know now?
Shilpa and Colin: Yes!

Where is the prize?

The solution starts at 1:30 in the 5:28 video linked above.

After chuckling at the seeming absurdity of the set up, we froze the video, as the narrator suggested, and I talked through the problem, alighting on the solution in a few minutes. The adult son seemed satisfied that I still had my wits about me.

However, I am always still looking for my eyeglasses.

Note: Wikipedia summarizes variations of these induction puzzles.