Thursday, October 29, 2015

Wow, This Amazing Puzzle Will Reveal How Stupid You Are! (Maybe)

You know the Wason selection task. You know all about Linda the bank teller and the conjunction fallacy. You're smart. You'd never fall for those things now! You know it's not more likely that Linda is a bank teller who is active in the feminist movement than that Linda is a bank teller. You know to flip the Wason card that would break the rule rather than the one that would confirm it. Yes, of course!

Here's one I learned in junior high school, which I've never seen studied. I don't know the original source. (If you do, let me know!) Maybe it will be fresh to you. Over the years, when I've presented it orally, I've found that even people with PhDs in philosophy often struggle, though really it's very simple.

A man is looking at a picture. He says,
"Brothers and sons, I have none,
but this person's father is my father's son."
Question: Who is in the picture?

If you think you know the answer, write it down. I don't want any squirreling around about what you had really been thinking!

After you've written down your guess, click through to this post on my Underblog for the answer and discussion.

[image adapted from here]

6 comments:

Rineke Verbrugge said...

A slight variation is in Jeffrey's Formal Logic, see https://books.google.nl/books?id=iqvsjhvZCgcC&pg=PA49&lpg=PA49&dq=brothers+and+sisters+i+have+none+but+this+man%27s+father+%22Formal+logic%22+jeffrey&source=bl&ots=rgil8VTVjt&sig=YxIut2HSik-tXMehH1GSOxdynFk&hl=nl&sa=X&ved=0CCAQ6AEwAGoVChMIkIfMnLToyAIVAs8aCh395gK6#v=onepage&q=brothers%20and%20sisters%20i%20have%20none%20but%20this%20man%27s%20father%20%22Formal%20logic%22%20jeffrey&f=false

I'm sure that wasn't the first occurrence of that version, though.

As to your version (which I like better), I don't know its origin, but I did find an occurrence from 2005 here, without the correct answer: http://www.librarium-online.com/forums/off-topic/50522-riddles-46.html

Luke said...

Drawing a diagram is the way to go. The same works for the Monty Hall problem, which has apparently stumped some maths PhDs!

Rhys Southan said...

I'm not sure if this is the original source, but this is in "What is the Name of This Book?" by Raymond Smullyan

Eric Schwitzgebel said...

Thanks for those sources, Rineke and Rhys!

howard berman said...

Do you suppose practice in perspective taking can improve performance on such tasks? Or is it hardwired? And is it linked to Dunker's functional fixedness? And do women or artist's or children fare better on this puzzle?

Callan S. said...

Monty Haul problem just seems to be bringing in rules (1,2 and 3) latter on. That's bait and switch.