A Quick Puzzle From OSCON

I recently returned from the O’Reilly Open Source Convention in Portland Oregon. In the final talk of the event, Paul Fenwick, always an amazing presenter, offered a puzzle during his talk that I thought I’d share.

I will offer the puzzle below, but the best way to experience it is to watch Paul’s talk, Mindware Upgrades For Fun And Profit.  No special technical or other background is necessary to enjoy it.

Albert is looking at Betty.  Betty is looking at Charlie.  Albert is a computer programmer.  Charlie is not.  Is there a computer programmer looking at a non-computer programmer?

What was most interesting to me is that the audience of about a thousand really smart people is then invited to raise their hands for “Yes” “No” or “Not Enough Information” and all but fewer than 10 people raised their hand for the same wrong answer!  I failed along with the vast majority, and the other wrong answer outweighed the right answer (which might have had zero votes… I don’t remember.)

If no one posts the right answer here after a while, I’ll come back with an explanation, but I do encourage you to go watch Paul explain.



  1. MathFan said,

    July 24, 2012 at 5:43 pm

    My answer is given below: [spoiler]I would have raised my hand for “Yes”.  If Betty is a *non-programmer*, then Albert is looking at her which satisfies the condidtion.  On the other hand, if Betty is a *programmer*, then she is looking at Charlie who is a non-programmer.  In either case, there is a computer programmer looking at a non-computer programmer.  Am I missing something?  Seems pretty obvious.[/spoiler]  

  2. jyoak said,

    July 24, 2012 at 5:49 pm

    MathFan, you’re right.  And it does seem fairly obvious now, but through some strange hypnotism, Paul made nearly every single one of us miss it.  Part of that is that both the context of a puzzle site and my mentioning that people got it wrong lead to deeper thinking.  In the moment, I guess we were tempted to casually accept the surface appearance instead of thinking.

  3. Chakolate said,

    July 24, 2012 at 7:54 pm

    I don’t know how to hide a spoiler, but it seems to me there are only two cases, and in both there’s a programmer looking at a non-programmer.

  4. MathFan said,

    July 24, 2012 at 8:00 pm

    I think you are right.  I hadn’t watched the video before but I think part of it was the limited amount of time allowed, plus perhaps the peer pressure of seeing others raising their hands. And you presented it all in one paragraph where he presented it with pauses and pictures which I found distracted from the puzzle.

  5. Paul H said,

    May 8, 2014 at 4:37 pm

    Hi, I just discovered your podcast today.  I listened to several episodes and really enjoyed them.  But it looks like you haven’t had any new episodes since 2012.  Do you have any plans to produce more episodes?

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