the wording feels worse because your subconscious is rationalising, as both the first and second rule are functionally identical. Remember that the first statement is the general form for conditional statements and actually should be easier if your a computer.
xpseudonym pseudonym exactly it takes a bit of more stress to emphasize that ONLY even numbers need to follow through with the rule. unlike the second one where it's made clear that ONLY below 18 year olds can't drink alcohol :)
I agree. It makes me wonder if people would get the first one right more if it said "If the number on the card's face is even, the card's back must not be blue." I think they would.
+Earl Wilbur A. Nogra "it takes a bit of more stress to emphasize that ONLY even numbers need to follow through with the rule. unlike the second one where it's made clear that ONLY below 18 year olds can't drink alcohol" - That's not true. Here is, word for word, both rules: "If a card is even, it must be red" "No alcohol under 18" Now lets switch these wordings to show that they convey EXACTLY the same information: "If a person is drinking alcohol, they must be over 18" "No even numbers if the card is blue" - Nothing is made more clear in the second statement, you just have a better intuative understanding of it since you are familiar with drinking laws.
You mentioned in the first problem that "one card breaks this rule, which card(s) must you flip to find out?" Your answer is: "The 8 and the blue". The thing is, by turning over the 8 and seeing it is red, I know that the blue card breaks it. If I turn over the blue and find an odd, I know the 8 breaks it. So the right answer should have been: Either the 8, or the blue.
+Mateja Petrovic only it would be wrong then. People under 18 could drink water, or milk, or not drink. The _true_ rule was the one he said, "people under 18 are not allowed to drink alcohol". Also I didn't find the second version simpler, but then maybe I'm an outlier.
This is 100% correct, the first example will only trick some people because of wordplay, the second example doesn't use the word play so less people will get tripped up on it (also because the first example was already explained and they are primed now)....the explanation in the video is less of a factor than this comment.
The video is made based on psychological studies, I'd imagine they didn't ask both questions to the same people, or the alcohol one only after explaining the first, there...
So I solved both pretty quickly, but it seems pointless to flip two cards in both cases. The riddle mentions that ONE card breaks the rule. That means that if we flip over the eight, and only the eight, and find out it follows the rule, the blue card, the only one that can break a rule now that we checked the eight HAS to be the odd one out.
The point is that even in blind experiments where the perticpant has never seen any variation of the riddle before, a much, MUCH higher percentage of people get the second one correct.
For the first one you only need to flip either the 8 or blue. because only 1 card breaks the rule according to the video, if you flipped the bad card, you know the other one is good, and vice versa. No need to flip both 8 and blue.
The answer you get for the first riddle in this video is absolutely wrong. 1. If a card is even, it must be red. 2. One card breaks the rule. 3. Your job is to fish it out. 4. If you turn a card that didn't have to be turned, it'll count as a fail. Answer: You don't need to turn both cards to know which of them breaks the rule. If you turn the 8 and it is red, it must mean the blue card has an even number on its backside. And because of 4 the answer you get in this video would be a failure.
This is incorrect. The blue card carries equal weight. Your idea assumes you can turn them over in some sort of order (instead of having to make all your decisions before flipping any over), and even then, it only has a 50% chance of being true. If you're still unconvinced, notice I could've said the exact same thing as you did, but swap the blue card with the 8 card.
Max Loh He is not incorrect. You're assuming that the rule breaking card needs to be flipped to determine that it is the rule breaking card, which is not the case. You only need determine it by process of elimination. given n cards that could be breaking the rule, you only need to flip n-1 cards to determine 100% of the time which card is the rule breaker. if one of the n-1 cards you flipped breaks the rule, you know it's that card. If none of the n-1 cards flipped break the rule, you know it can only be the last card you didn't flip that breaks the rule. This works in both scenarios of decision making; It doesn't matter if you have to choose all the cards ahead of time, or you have to flip them in a certain order.
mondere Yes, you are right; my original comment is incorrect. I guess the video maker should not have included the "exactly one card breaks the rule" constraint when trying to illustrate this phenomenon. Then everything would've been dandy.
You cannot infer what is on the other side of the blue card. You are correct, in that only one card needs to be selected; but that's not because the other card can automatically be deduced to break the rule. It's because the rules clearly state that only one card card is incorrect.'
in the first problem the question makes you assume that only even numbers must be red and uneven numbers must be blue, if you would add something like "uneven numbers can be blue or red" it would be more understandable and thus easier
"in the first problem the question makes you assume that only even numbers can be red and uneven numbers must be blue" Which question created this assumption? The only question he asked was: "Which card(s) should be turned over?"
+juhotuho10 How come he didn't have to state that people over 18 could still drink non-alcoholic beverages then? There's nothing wrong with the first question, you're just bad at logic. The "If" statement is very different from "if and only if" (usually abbreviated to "iff"). It doesn't help that in English we don't have a single word for "iff", and oftentimes "if" and "iff are used interchangeably because we are lazy speakers. If we did have two separate words, our social decisions would be less prone to fallacies.
To my knowledge - in abstract logic, the problem is essentially like this: If A, then B However, our intuition has the tendency to tell that the logic can be vice-versa (it becomes "if B, then A"), when in fact it can't. The fallacy is called "affirming the consequent"
You kinda blew it by showing the answer before introducing the second variant, because now I don't know if I got the right answer because I knew the logic from the previous example or was it because of the nature of the second variant.
I know some of you will probably get both but did you feel like the drinking riddle was much more intuitive to get than the even number/colour riddle? Anyway, the next video will be about transfer and education in general. Feel free to share any thoughts you have on education as I'm sure you've had your experience. Also lastly, because I've decided to switch to more in depth videos for a while, I'm going to do small riddle videos on the side in the meantime (like this one), just so you guys have something more frequent to look forward too. Quick shout out to Psych2Go, another psychology channel ru-vid.com And see you soon.
Nice riddle and I hope you keep them coming :) but...Mister Spock tells me that your logic is flawed : I would only turn one card. I'll explain : - first the rule is : "if a card is even, it must be red" (then only 2 out of 4 card matter) - 0:17 you say that "one of these card breaks the rule"
Ahhhhh nice thinking. That is correct. I reworded the original question which just said "which card should you flip to determine whether the cards follow the rule". My mistake but thank you for picking that up
I thought the number/colour riddle was more intuitive because I didn't even know what was the question for the second one. I was only given the information "No alcohol if you're under 18", but I had no idea what I had to do with it, so I went out of my way to pick the orange juice card and 41 card because I thought I assumed the drink and age to myself by picking said cards (so I wouldn't break the alcohol restriction rule). If you would've just added a directive like "Bust the people who aren't drinking legally" after the rule I guess it would've been more intuitive, but I think it's just confusing as it is in the video lol EDIT: Actually nevermind, I just didn't realize the second riddle had the same principle regarding one card breaking the rule and me having to figure out which card it is. I'll let you decide whether it was your fault for not repeating it for the second riddle or just my stupidity.
I think the 2nd one is easier is because we don't have to think about the drinking rule because it's well known . I actually paused the video at 0:14 and tested each card to see if it can break the rule. I did it because the "even => red" rule was new for me, but for the 2nd one there was no need because "everyone" knows it. I am 99% sure that to someone who doesn't know about the minimum drinking age , the riddles have the same difficulty.
"Domain knowledge matters most" could be another formulation of the conclusion drawn from this. The psychological experiment regarding argumentative theories of reasoning is one thing, but there is an interesting second perspective on questions like this. It is a kinda funny perspective on job interviews. Thomas Fig used the same example to make a point about hiring people for Jobs. Often HR people ask general questions to gauge possible employees like "why are manhole covers round?" and the response should NOT be trying to answer the question but to leave the interview and wishing the HR person good luck in finding a good company to work for in the future, being thankful that they have shown you how awful it would be to work there. If someone asks you such a question he better be a psychologist doing an experiment, NOT a HR person. Such questions have only one real value in job interviews, namely to tell you that the management is crazy and never gets into the background of any project and only asks arbitrary and stupid questions, AND these questions in the interview is just there to filter out the sane candidates (who will leave soon again) from the insane ones (who might take this for a longer time). ;)
I'm sorry to say that you would have failed. Turning over the 8 was unnecessary. Turn over the blue card and it's even, then you win. Turn over the blue card and it's odd, then you know that the 8 card must be the one that breaks the rule (as the question specifies that only one card breaks the rule). Equally, you could turn over the 8 card only, and achieve the same result.
I think he phrased the question wrong. Typically you have to provide a solution that proves or disproves the rule and always works with no guess and check. this version requires both cards to be flipped
rather confusing instructions in that it appears by the directions that only one card can be turned, whereas the solution permits two cards. If it relies on the ambigous statements at the beginning of course you will trick/confuse people.
There is a mistake in the first task: You task is to find the one that doesn't follow the rule. But you know that only 2 Cards CAN break the rule, so you only need to switch one. If it is the one that breaks the rule, you got it. If it doesn't break the rule the other one must break the rule. Or have I misunderstood the task?
false equivalency, "these two puzzles are exactly the same." their logical sum is the same but the statements are not. one is, "if this then that." the other is, "not this if that."
or phrase it the same, "all even cards must be red." and the puzzle is trivial ... or go ahead and match identically, "you can't be blue if you're even,"
The statements are different, but resolve with the same logic. The logic from riddle 2 is perfectly applicable in riddle 1, but we don't apply it because we don't recognize the same logic in a different context. Phrasing riddle 1 identically lets us transfer the logic over because we recognize the context, so yes the puzzle becomes trivial.
This goes into assumptions created by the statement itself. Logic is dropped by the listener in favor of a quicker solution - when the statements are different you will get differing quick answers. That's what I believe Camilo was pointing out (and you're both correct) ... when you have 4 items and 2 are named directly, the average person will focus on those 2 even if it brings an illogical conclusion. Hence "bite size psych" and not "bite size logic".
Yeah, logical equivalence is not the same as "same puzzle." Logically "tell me the largest prime less than one hundred" is equivalent to "say the words 'ninety-seven'" but most people will find the first riddle easier.
Logical equivalence does make it the same if the gap between the logic (that is to say, the number of logical steps needed to go from one statement to the other) is few. It takes a lot of logical steps to conclude "largest prime less than one hundred" is the same as "97," but it is only a single step to go from an "if statement" to its contrapositive. I think what's illustrative of this is that people don't have an intuitive sense of the idea of "if."
eddie howell not really annoying unless it's done more than three times. That's when it goes to be unoriginal. At least call it something that would make sense as an insult like "oh god, so original" since the first reply was patronising sarcasm. Either be an ass properly, or not at all.
from a purely logical standpoint, probably not. from a standpoint of knowledge, it is: we already know alcohol is not allowed for people under 18 in many parts of the world. we don't need to go through a comprehension process that takes time in order to understand this rule. the card rule is completely arbitrary and unknown to us beforehand. it might as well be the other way round. we have to invest time in order to understand it. one riddle is set up to cater to us, the other one is not, therefore there is an objective difference in difficulty.
CaptainObvious0000 Not exactly... Since the first problem simply presented us with four cards and a basic rule. The second problem however, presented us with four cards, a just as basic rule, but the mind is then having to deal with all the information behind it. This can go two ways off the top of my head. I agree with Gillian because I've seen the first problem before a while back and knew how to work it out. For returning, the first one is easier. HOWEVER; I also agree with you, since for beginners who don't understand how to work it out, the second problem is better at explaining the methods used to figure out the problem. In conclusion, the first problem with basic rules is simpler, but it's a lot harder to figure out the method from just the basic rule. The second question presents us with a story we can relate to. This can be expanded on mentally to understand why we would only need to turn over two cards. Since any doubt from the first question is already cleared up by the story behind the second question.
Another reason the drinking riddle is easier is due to how the rule is structured. In mathematical logic, events or facts can be represented by letters, and relations between these events as symbols. For example: if it rains, then the road will be wet. The events "it rains" and "the road will be wet" can be represented as the letters P and Q, respectively, and the relation "if... then" can be represented by an arrow: P --> Q. Another symbol is the ~, which expresses the negative of an event; therefore, "it doesnt rain" can be represented as ~P. The first riddle involves the events "the number is even" and "the card is red", in a direct relation P -->Q. The second riddle involves the events "the person is under 16" and "be allowed to drink alcohol". But the relation is actually a negative: P --> ~Q. And the negative is easier to identify is turning the vodka card, or the blue card (which is just ~red).
Could you make a video explaining why school is either useful or useless. There seems to be a lot of non factual videos explaining why school is or isn't important and I just want to know the truth.
That is not a topic that can be adequately addressed in a short video. There are so many perspectives on this, so many articles and books written on the topic. I think most people can agree school is not optimally formatted for learning, though there's fairly large disagreement on what changes would most improve it, or how we would measure said improvement. The answer you get will likely depends on how you define school, and what you think the benefit of it is or ought to be. If you're interested in the topic, there's a really good book called "How Children Fail" by John Holt (a former teacher). It's not very long, but it is quite interesting. It's primarily a collection of notes and observations he made of his classroom and the classroom of one of his colleagues. It was written in the 60's, so it's a bit old, but schools haven't really changed since then, and his observations are as true today as they were back then. They certainly rang true with my own experience working in a classroom. Although the book is called "How Children Fail" what it really addresses is how the structure of the school system sets children up to fail (at gaining real, transferable knowledge and understanding--not necessarily at failing at school). His followup book, "How Children Learn" addresses just what the title suggests. From what I learned getting my degree in psychology, what he talks about lines up pretty well with the research on how children learn. Long story short, people learn best in playful settings (and school is pretty much the opposite of play, though the more play-like it can become, the better chance it has of being a useful learning environment for children).
School (academic learning) is useful to people for many reasons. Anyone who says it is useless is probably unaware of how much they use academic knowledge. Essential day to day tasks are much harder without the ability to read, write and calculate well. Now sure there might be an aspect of academia that you felt wasn't particularly relevant to your life (people usually say geometry as an example) but there are many instances you can use geometry without realising it. Sports, architecture, design, woodwork, computing etc.
I'm assuming you're writing about high school, but my comment will apply to college as well to a lesser degree. Even if you feel like school is just teaching you a bunch of useless things that you'll never need again, it's still incredibly important. Just by processing that information by memorizing things, calculating things, writing things, etc. in all those different subjects you're increasing your ability to process and retain new information for the rest of your life. No matter what you want to do with your life, that ability is pretty vital to interacting with the world around you. I didn't go to school as a kid and it was indescribably difficult to adjust to college in so many ways, and even now after I got into a stride and earned a STEM degree with a pretty good GPA, missing out on school in my formative years has caused me a lot of difficulty. I feel like I have to try five times as hard to accomplish what most people can without much effort, and if it hasn't gotten much better by now it probably never will. Basically, going to school as a kid/teen is worth SO MUCH MORE than the facts you memorize or equations you learn. That said, I've had the most random things from some of my early courses in college pop up as being useful in unexpected places. You never know when it'll help you to have some piece of knowledge in your back pocket.
I think the 2nd one is easier is because we don't have to think about the drinking rule because it's well known . I actually paused the video at 0:14 and tested each card to see if it can break the rule. I did it because the "even => red" rule was new for me, but for the 2nd one there was no need because "everyone" knows it. I am 99% sure that to someone who doesn't know about the minimum drinking age , the riddles have the same difficulty.
These riddles have an unwritten second rule that complements the first. "If the number is even, the other side must be red" also means "If one side is blue, the number must be odd" since cards with an even number must have red on the other side. "If you're under 18, you're not allowed to drink alcohol" means "If you're drinking alcohol, you must be older than 18". The cards you pick must confirm both the written rule and the unwritten one, which is why you should pick 8 and blue, and 16 and vodka.
Actually, you are misinformed, slightly. The "second rule" is one that you assumed to be true, but very well could be false and the riddle as is would remain intact. The initial rule was that an even number has a red back, therefore an odd number could very well also have a red back. Correlation does not imply causation. Meaning just because you're told that even numbers are red backed, you shouldn't assume odd numbers must be blue backed. It seems like an obvious logical method of reasoning, but in certain environments, that quick assumption can cause significant errors in your perception of mentioned environment.
MadeofAwesome4ever is right, though. The rule is an implication: [A - > B] (if even, then red) With that You also know: [not B - > not A] (if not red, then not even - OR: if blue, then odd) What You mean (if odd, then blue) is of the form: [not A - > not B] and is indeed a wrong assumption. But MadeofAwesome4ever (weird name, by the way) never said that to be true.
If you think that there is an automatic second rule that if the side is blue then the number is odd, then you are inventing a rule where there is no reason. You cannot make the assumption that you can infer anything about the color of ODD numbers nor the odd-even status of BLUE cards. That's the entire point -- if you jump to that conclusion, then you are being illogical.
+Lemon is correct in illustrating. More technical, the contrapositive is equivalent to the conditional. If A then B is equivalent to If not-B then not-A. Upon further thinking, +MadeofAwesome4ever hits upon the key difference. The riddle requires one to focus upon what conforms to the rule thus need to check every card versus the underage drinking rule the focus is upon rule breakers thus only need to check the potential violators, those under 18 years old. In the Real World situation, we do not care about the above-18 drinking non-alcohol so we do not need to check what everyone is drinking.
+PhrontDoor You can actually "invent" that rule, as the other commenters have shown. It's called "modus tollens," if you're curious. This might be more obvious. Consider this statement: "If you are younger than 18, you are a 'minor.'" Suppose I ask a friend of mine about person X, and my friend says, "X is not a minor." I know by modus tollens that X is not younger than 18. This is true by definition. If they were younger than 18, they would have to be a minor, so if they're not a minor, they must be 18 or older. Here's one more: "All cats are mammals." (If X is a cat, X is a mammal.") "X is not a mammal." "Therefore, X is not a cat."
Basically it's abstract vs concrete. Red and even numbers are abstract. Alcohol and imagining someone at a certain age is concrete. So, it's easier for us to understand.
Honestly I think part of the intuitiveness is due to the phrasing. I think the first puzzle would be slightly easier if it was phrased "If a card is even, it must NOT be blue" which is more of a direct analogy to the drinking example. This doesn't detract from the fact that being primed for a solution from real-world familiarity helps, but it does make the example here a little less persuasive.
mike garcia But you still failed following the instructions. Let's say the rules were: if you turn over more cards than necessary all your loved ones would be killed. So by turning over all the cards, sure you would solve the riddle in good time but hey, all your loved ones would be dead. Worth it? Well the killing part perhaps's a bit harsh =/ But point is, there will be times in your life where using your brain instead of taking the shortcut will be necessary. So instead of coming up with some bullshit excuse why you failed this riddle, apply yourself harder next time.
its not harder its just easier in the 2nd one because we were told how to solve the problem in the first one.if you were given the 2nd one first, we would have the same problem wether we were over thinking or just not understanding the problem
I was confused in the beginning. It was not clear that you were supposed to turn over any number of cards to verify that all cards were compliant with the rule, and the question is which card(s) do you then turn over...
I would say you only have to turn one card: no. 2 with the 8? If it's non-red, that's the rule breaker. If it's red then card 4 must be the rule breaker since the rule doesn't apply to card 1 and card 3 can't violate it. Am I wrong?
agree, the speaker sad that only one is violating the rule. if he would have said: find all cards that violate the rule, than his solution is need. however, in this case the riddle actually has two solutions, the one you said and the one with the same logic but for the card no. 4
Technically you only HAVE to flip 1 of the cards. Either flip the 8 OR the blue. You can do this because we know that one of the cards breaks the rule. Therefore, if the card you flip beaks the rule, you found the card. Otherwise, if the card you flip adheres to the rule, you know the remaining card must break the rule.
I take it this way, First problem mentioned that "if a card is EVEN, it must be RED" Second one is "no ALCOHOL if you're under EIGHTEEN" Take a look at the keywords in both the problems, The first one has keywords EVEN and RED so we tend to look at the red card and the even card, whereas see the second problem which has the keywords ALCOHOL and under EIGHTEEN so we tend to look at alcohol card and 16(under eighteen) card. It is just the matter of what words are used in framing the riddle. If the first riddle was framed as "no BLUE card should be EVEN", it would have been a much easier riddle and the difficulty of both the riddles would be same.
I don't think the difference lies in how difficult it is to apply the logic, but rather in how difficult it is to parse/understand the problem. For instance, the second version better communicates the problem by getting rid of a potential misunderstanding. In everyday language, we rarely say things like "if and only if", often simplistically substituting it with "if". Consequently, when we hear "if" we sometimes (depending on context) assume the speaker meant "if and only if". The second version's context makes it clear to the viewer that by "if" you really mean just "if".
Comments that attempt to discredit others are from disbelief or the need to gain recognition. I do not need prove whether I solved this or not. It is common sense which make make it harder for some to reason with. This is mearly a fact checking riddle to see if the statement is true or not. There's no reason to check the things not mentioned only the things that are, never take things ate face value.
Honestly i feel like these two aren't that different, but since we were not familiar with the rules and hade to take a second to comprehend the assignment, the first one seemed harder. Once we knew the rules clearly, we completed the second one with ease. Also, the second one was easier since the drinking age rule is ingrained into our minds since an early age, so putting it to practice was child-like simple. On the other hand, the even color rule was new to us, so again it took us a second to learn the rule. Its like saying "our brains are so mysterious, i can spell my name backwards faster than *insert unfamiliar word* backwards"
no this is wrong. sorry this is this is really dumb. you know why the second one was easier? because you literally gave the same riddle twice and put the cards in the same position and expected us not to remember something we watched 20 seconds ago?
The first one was formulated in a more tricky way. Also, the second was easier for me because I just was shown the solution of a very similar riddle just seconds before. The fact that I was shown the solution to a trickier riddle made it easy for me to solve the second one...which actually seems to support the school system...you get a lot of complicated and detailed information in order for you to find it easier to deal with random everyday life situations
I got this correctly without any problems. But found the first one much easier to process. I'd wager that it's because of the mathematical terms just being more defined in my head.
I found the first version of the riddle extremely trivial, and the second version harder. The second version simply contained more information since it was less abstract, so it was harder.
Actually, you only need to turn over the blue card (we can discard the red and 11 as mentioned in the video) because we are told that only one of them breaks the rule. Let me explain In the first case, if the blue card is turned and is even, then we know it breaks the rule, and the 8 does not as only one breaks the rule In the second case, if we turn over the blue card and it is odd, the eight must break the rule as it is the only card left to break the rule The same logic can be applied to only turning the eight
The 1st one is a trick question. The rule is "if a card is even, it must be red". The rule does not define a "vice versa", so the rule "if a card is red, it must be even" is nonexistent. Therefore the real answer to the first question is to flip only the "card 8"!
Yes the only rule stated was about numbers not colours. so in fact if there definitely is one card that breaks this rule it must be the 8 card so there is no need to turn any card over as you know it is that card already
This was also my first instinct which I quickly recognized as wrong when presented with the answer. You must flip the blue card too in case it's even. Even cards aren't allowed to be blue.
If you know that exactly ONE of them the breaks the rule (no more, no less), it's sufficient to turn over just one card, isn't it? Either the blue card or the even card, because if the card you turned is not breaking the rule it must be the other... That depends on a very pedantic understanding of "one of these cards breaks this rule", of course; but such puzzles usually requires pedantic and literal interpretations...
This is why learning math through application is easier for most people. If you can relate it to a real-world situation, the problem becomes more than invisible concepts, but a situation we can actually observe.
The two statements are not alike. "No alcohol" is prohibition, which is something very different. I bet if you say "No blue back when a card is even" then most people will get it right.
Or simply "if a card is even, then it must not be blue" instead of "if a card is even, then it must be red." If you were presented with both these statements side-to-side, you'd probably say they were exactly the same, and logically they are, but day-to-day usage of English makes you think of them differently.
thezebov is right: one riddle has the pattern "if A than B", and the other "if A than NOT B"... but still, without being told that one is "harder" they both seem pretty much the same level of complexity.
You didn't specify that you could turn more than one card in the first riddle, but the one card I did guess (the 8 card) turned out to be one of the correct ones.
I didn't understand what you were asking me to solve for until you gave me the answer. Then it was obvious that you wanted me to check if the rule was being followed.
Please create a version two of this video and swap the riddles? I want to see people's reactions to see if knowledge of the riddle changes outcome of the answers.
The riddles aren't the same. If you had said, "only juice if you are under 18," then they would be the same, and people would choose 16 and juice if they didn't get the concept. Also, if you said, "blue can't be with even," then everyone would have gotten it right
Wording of 1st scenario is: "ONE of these cards breaks this rule". Hence becomes unnecessary to flip both "8" and "{blue}". So flipping both results in failure!
It's harder because you didn't clarify until afterwards that you can flip over more than one, but that information was provided for the second problem.
This is interesting. In the first riddle I assumed that 'even must be red' implied that 'odd must be not red' which is a false assumption. But when you use the numbers and drinks I wouldn't assume that 'under 18 gets no alcohol ' implies that 'over 18 must get alcohol'. Without the false assumption it's easy to solve.
Knowing that A implies B is equivalent to not B implies not A, those problems are really easy: One should check that if you have A, you also have B or equivalently if you don't have B, that you don't have A. In the first problem, you can see A as the proposition ''The card is even'' and B as ''The color of the back of the card is red''. Hence, if you have an even card, you have to turn it to see if it is red and if you know that you don't have a red card you have to turn it to see if it's not even (so if it's odd). The same rule would applies if there were 3 colors (say red, blue and green) and 3 type of numbers (say positive odd, positive even and negative). If the rules was again: ''If a card has an even positive number, than its back is red'', you should return only those with an even positive number on and those with a blue or green back.
So the reason the first riddle was shared for me was because I honestly didn't really understand what he was trying to get me to do. Once he explained it the second riddle became easy. Not because that version is easier but because I had an understanding of how the game/riddle works
Why I couldn't solve the first puzzle is because I assumed all odd cards needed to be blue. If I realized the odd cards can be both colors, this would have been just as easy.
I suspect the context that makes such a difference here is that we all start out as under-18-year-olds who therefore must be non-alcohol-drinkers, so we're used to thinking about the contrapositive of "if you drink alcohol you must be 18 or older". While most people don't even know what "contrapositive" means in the abstract, and so don't always see any if-A-then-B statement and automatically grok that it's the equivalent to an if-not-B-then-not-A statement.
8 years later I still remember this simple rule from geometry. For a logic if-then statement, the contrapositive must be true, but the converse and inverse are not necessarily true. So if a card is even, it must be red and on the contrapositive, if a card is blue, it must be odd. The other two combinations are irrelevant and don't need to be checked.
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The 2nd riddle is easier because the rules are more familiar to the average person. I've taken some programming and math proofs class and both riddles were pretty much equal to me. I've noticed that most people just get taken off guard when you introduce variables and abstract conditions, but normally they adapt very quickly with some practice.
The key to understanding this is that even cards must be red, but red cards don't have to have even. So turning an odd number card is pointless and turning any red cards is pointless. This could be 10 cards and again you only need to turn even numbered cards and blue cards. It took me ages to understand but now I totally get it.
To generalize, If A then B means If not-B then not-A. Language is powerful. Repeat that sentence when you encounter real life scenarios where that logic is used and in time you'll generalize it more. EDIT: In logic this rule is known as "modus tollens".
Fun fact friday, these two riddles aren't the same and familiarity isn't the only factor at play. The first riddle with the colored cards states: if a card has en even number, the other side must be red. From this statements 2 rules should be drawn: a) the red side of an even number has to be varified. b) the other side of a blue card cant be even While the second statement results in slichtly different "rules". From the second statement ("no alchol if under 18") the following rules can be drawn: a) if you are under 18 the other side cant be alchol b) if you are drinking alchol than the age on the other side must be over 18 In the second riddle the rules you have to conclude effect the items being mentioned. alchol, so i turn over all alchol, under 18, so i turn over everything under 18. Not much thinking required. While in the first statement not both objects mentioned are the objects your concluded rules aplly to. even, so i turn over even. red so i turn over red. Done , and wrong. So even though the probblem might seem the same, the way it's told actually influences the outcome. This does not exclude the effect the setting might have.
