A bat and ball cost $1.10.

    The bat costs one dollar more than the ball.

    How much does the ball cost?

Then read this article

"Everything was made up by people that were no smarter than [half of] you." -what Steve Jobs should have said?

5 cents

Some of the comments on that article are INSANE.

I get how people can get it wrong.

I don't get how people can then not understand when its explained.

Got it wrong! Gurtie's answer made me realise though.

Quote from: Gurtie on September 03, 2015, 08:01:19 PM
I get how people can get it wrong.

I don't get how people can then not understand when its explained.

The comments wouldn't load for me on that page, but....

It's called the Dunning-Kruger effect because of an influential paper by Dunning and Kruger! They did things like gave people a grammar test and then had people rate what percentile they were in. Then they gave people access to tests from other people and had them rate their grammar skill again. Less capable people make the smallest adjustments. They've redone the studies with other fields (comedy event).

The abstract from the most influential paper (2406 citations):

QuoteSuccessful negotiation of everyday life would seem to require people to possess insight about deficiencies in their intellectual and social skills. However, people tend to be blissfully unaware of their incompetence. This lack of awareness arises because poor performers are doubly cursed: Their lack of skill deprives them not only of the ability to produce correct responses, but also of the expertise necessary to surmise that they are not producing them. People base their perceptions of performance, in part, on their preconceived notions about their skills. Because these notions often do not correlate with objective performance, they can lead people to make judgments about their performance that have little to do with actual accomplishment.

source: http://cdp.sagepub.com/content/12/3/83.short (abstract; full text behind paywall).

The followup paper from 2008 has this abstract

QuotePeople are typically overly optimistic when evaluating the quality of their performance on social and intellectual tasks. In particular, poor performers grossly overestimate their performances because their incompetence deprives them of the skills needed to recognize their deficits. Five studies demonstrated that poor performers lack insight into their shortcomings even in real world settings and when given incentives to be accurate. An additional meta-analysis showed that it was lack of insight into their own errors (and not mistaken assessments of their peers) that led to overly optimistic estimates among poor performers. Along the way, these studies ruled out recent alternative accounts that have been proposed to explain why poor performers hold such positive impressions of their performance.

src - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702783/ (full paper).

I feel that nothing protects one's modesty like knowing about the Dunning-Kruger effect. Since learning of this when the original paper came out, now I can never think "I'm really good at that" without thinking "Or maybe I'm just totally incompetent and therefore don't know what actual competence looks like."

Like for example, I feel like I'm really good at giving short, concise answers ;-)


"One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision"

- Bertrand Russell (1951)

The problem is sort of a math illusion.  Most people I've asked in person have gotten the answer wrong at first -- only one person got it right, I suspect that she knew that it was a question she needed to think about before she answered.  I asked a guy with a masters degree in Mathematics and he got it wrong too. 

I came across the question in a lecture where it was given as an example of how quick, instinctual judgements could be wrong sometimes even though they serve us well on a daily basis.  Its a type of mental reflex if you will, works most of the time and makes decision making less of a burden.

Personally, I knew there was some type of angle to the question and that my $0.10 answer was wrong, then I thought a bit more about it and was like "oh year, it has to be $0.05!".  I suspect that the 50% number at those prestigious universities would have been higher if he students were not on guard.

As for those folks who can't accept that they are wrong what you said Ergophobe sounds right to me.

I got it right, but it was the fact that it was asked that made me stop and think before answering. In another context I think would have just gone for $0.10 without thinking.

That and I've been reading a book called Calculated Risks lately that walks you through probability math way more complex than that (like over 90% of physicians get the medical questions wrong and 90% of lawyers get the legal questions wrong). But after you've read the book, you'll never get those questions wrong again.

>> I got it right, but it was the fact that it was asked that made me stop and think before answering

me too, although I tend to be good at these type of questions (at least, I think so!!). I am horribly bad at others. When I was at school I also had a teacher who really drove home to us the importance of reading a question properly to the end before answering it, which helps as it forces you to slow down and reframe the question.

Quote from: Gurtie on September 05, 2015, 08:37:45 AM
When I was at school I also had a teacher who really drove home to us the importance of reading a question properly to the end before answering it,

You're going to get destroyed on Jeopardy ;-)

I refer you to

>>  I am horribly bad at others


Yet another book on my 'to read' list

>the importance of reading a question properly to the end before answering it

Same, first year of 'science' at high school the teacher went at length to insist we done this before any kind of experiment. Of course, no one did and the result was something like 'i am a dummy'.

In day to day life we condition ourself to make quick decisions based on effort & pay off. e.g. crossing a road, it's not important to know how far away oncoming traffic is when 'far enough' will do.

It's amusing seeing the ego in the comment section.

I saw this a few years ago and got it right then and now.

I think that says more about me than the question though. I'm not clever, I just think in weird ways, or as my other half said recently "Aspergers as fuck!"