Jack is looking at Anne, but Anne is looking at George. Jack is married, but George is not. Is a married person looking at an unmarried person?
(a) Yes
(b) No
(c) Can not be determined
***
If you chose (c) as the answer, you’re wrong! Here’s how, and also why:
And the answer is the first option. But over 80 percent of people choose the third option. Here’s the solution: the puzzle doesn’t say whether Anne is married or not, but she either is or she isn’t. If Anne is married, she’s looking at George, so the answer is “yes”; if she’s unmarried, Jack is looking at her, so the answer is still “yes.” The underlying reason why smart people get the wrong answer is (according to the article) that they simply don’t take the time to go carefully through all of the possibilities, instead taking the easiest inference. The patience required to go through all the possibilities doesn’t correlate very well with intelligence.
This is from Cosmic Variance blog on the Discover Magazine.
[If you liked this brain treaser, you might also enjoy A Mathematical Conundrum.]
Blank Slate 
I hvae always believed that ‘intelligence’ itself is a highly subjective term and intelligence as measured by I.Q. tests capture only one aspect of the human mind. Also people who are considered ‘smart’ in some aspects may be totally clueless in other areas.
People might have an aptitude for a particular aspect like logical and mathematical skills, but that only means they’re good with number crunching and nothing more. I think I.Q. tests are way too often misused for measuring something as abstract as intelligence. As you have rightly pointed out patience is a skill too and a very important one at that.
Yup, I agree that “intelligence” – as it’s used and understood generally – is a subjective term.
I came across this related article on Hindu about a month ago: “Who is more intelligent? Ramanujan or Tansen?” Most of us would answer that Ramanujan was far more intelligent than Tansen, and we would be technically correct (although there’s no way we can empirically validate that).
But intelligence is hardly unidimensional. Verbal, musical, interpersonal, intrapersonal are some of the factors of intelligence (as suggested by the article) that are not considered in the standardized measurement through the means of I.Q. tests.
Anyways, I just thought that this puzzle that I’ve posted in my post was a nice way to show that (as argued in the linked article) the reason why 80% of us chose option (c) is not due the lack of intelligence, but in spite of our intelligence (which tends to make us impatient).
This reminds me of one of my favorite math proofs: An irrational number raised to an irrational power is at least sometimes rational.
Proof: Write (sqrt(2)^sqrt(2))=x. Then x^sqrt(2)=2.
x is either rational or irrational. If it’s rational, then sqrt(2)^sqrt(2)=x is the required example. If
it’s irrationa, then x^sqrt(2)=2 is the required example.
As with Mary’s marital status, we don’t need to know whether x is rational. (In fact it’s not, but that’s hard to prove and we don’t need to know it). Either way, we have our example.
That’s neat!
Thanks for stopping by and for your comment. I’m really looking forward to read your book.
Pingback: Rational Irrationality at Steven Landsburg | The Big Questions: Tackling the Problems of Philosophy with Ideas from Mathematics, Economics, and Physics
Pingback: The Monty Hall Paradox « A Blank Slate
Made for a good reading this. I would rather view the ‘third option answer’ to the eagerness to answer the quickest. Human mind treats any puzzle as a ‘personal challenge’ – a litmus test in the race to be amongst the creamy layer of ‘intelligentia’.
And that “eagerness to answer the quickest” seems to correlate well with intelligence.
Both smart and not-so-smart people often get this answer wrong… but due to different reasons.
Pingback: Conjunction Fallacy « A Blank Slate
Pingback: Thursday night quiz: rationality brain tease - zupped