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the psychology of reasoning is a branch
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of cognitive psychology that studies the
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way in which humans use logic to come to
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conclusions based on available
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information but not all reasoning is
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valid and people may use invalid
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reasoning to come to a logical
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conclusions suggest how logical are we
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as humans and for that matter how
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logical are you a logic test developed
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by Peter Watson in 1963 revolutionized
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the field of reasoning this classic
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selection task features cars with laters
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on one side and numbers on the other
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side subjects are then presented with
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four cars and a rule if a card has a
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vowel on one side it must have an even
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number on the other side and the task is
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this which card or cards must be turned
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over in order to determine whether or
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not the rule has been followed so
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basically you must turn over cars which
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can guarantee whether this rule is true
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or false I'll give you a few seconds if
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you want to pause the video and think
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about it before revealing the answer
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okay the correct answer is this the cars
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which must be turned over r-e + 7 these
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are the two cars which must be turned
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over to assess whether or not the rule
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has been followed
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Feeny's studies have shown an extremely
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poor results for tasks less and which
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will be 4 percent of participants get
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the correct answer the most common wrong
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answer been e + 2 this can possibly be
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explained by confirmation bias the rule
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mentioned put a vowel and an even number
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so it may seem logical to choose the
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vowel and the even number cards well
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this means seem logical as I will
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demonstrate is actually fundamentally
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illogical I'll now go through each card
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and explain why you do or do not need to
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turn each card over the keys test asked
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is that you need to understand that you
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must try to falsify the rule not confirm
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them so the first card II this is the
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most obvious unfortunately all
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participants creately conclude that this
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card must be turned over because of
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course if there's an odd number on the
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officers say the rule has been broken
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and in the next card
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the key card lists basically an
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irrelevant card which cannot give us any
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information if we turn it over and it's
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an odd number
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that's fain if we turn it over and
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that's an even number that's also thing
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so if neither outcome breaks the rule
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there's no need to turn the card over
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the 2 card is where things get tricky
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and where most participants slip up if
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we read the rule again if a car has a
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vowel on one side it must have an even
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number on the other side now what's
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important to realize is that this Beryl
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only goes one way therefore we cannot
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conclude the if there's an even number
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on one side there must be a vowel on the
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other side this is not the case if we
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turn over the 2 card and there's a
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constant on the other side that's pain
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this does not rate the room and
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obviously if we turn the card over and
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there's a vowel this also doesn't break
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the rule so again if neither outcome can
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break the rule then we cannot obtain any
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relevant information from this card and
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therefore there's no need to turn over
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finally the 7 car this card must be
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turned over why to make sure there is
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not a vowel on the other side if there
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is this breaks the rule because the car
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has a vowel on one side and an odd
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number on the other shape so looking at
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both potential outcomes of all four cars
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we can see that there are only two ways
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in which the rule and
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broken and therefore these two and only
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these two cars must be turned over this
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rule is basically an F a.m. statement or
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it can be written as P therefore Q and
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which P is the antecedent and Q is the
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consequent each of the four cards
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represent the four possible premises P
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not P Q not Q so P would be a vowel
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naught P would be a consonant cued being
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even number and not Q would be an odd
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number
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now when presented with each of these
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premises we can make inferences this can
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be divided into two types of reasoning
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inductive reasoning and deductive
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reasoning inductive reasoning is invalid
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while deductive reasoning is valid the
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first time was obvious is when presented
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with P and less example the a card since
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the rule is P therefore Q given P we can
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obviously deduce that Q must fall this
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is known as affirming antecedent or
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modus ponens which is a valid deductive
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form of reasoning next when presented
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with naught P and less example the key
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card Rakuten fair not Q this is known as
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denying the antecedent which uses
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inductive reasoning and is therefore
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invalid just because you're presented
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with naught P does not necessarily mean
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that naught Q must fall when presented
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with Q people often in fair P but like I
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said the rule only goes one way so just
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because the rule is P therefore Q does
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not mean we can turn around to see Q
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therefore P this is known as affirming
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the consequent which is another invalid
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form of reasoning now finally when
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presented with naught Q we can fear not
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P this is often missed by participants
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of tasklist despite it being a valid
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logical form of reasoning known as
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denying the consequent or modus tollens
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this is valid because if we have not
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cured only logical conclusion would be
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not P if we apply our real-world example
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we could say something like all Tigers
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have stripes as our premise then we
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could make inferences using both
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inductive and deductive reasoning for
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example if it's a tiger it has stripes
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if it's not a tiger it doesn't have
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stripes if it has drapes it's a tiger if
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it doesn't have stripes it's not a tiger
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looking at the results of the card
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selection task one mate quickly Jones to
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conclusion that humans are not very good
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at reasoning and therefore illogical but
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one important thing to know is that
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content is crucial to a task like this
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participant performs significantly
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better when presented with cars that
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have real-world applicable examples this
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can be seen in a different form of the
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car selection task this time each car is
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represented by a person on one side of
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the car is a drink in which that person
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is drinking and on the other side is
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their age participants are presented
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with four cars and falling rule if a
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person is drinking alcohol it must be 18
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years or older the task is once again to
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turn over cards in order to determine
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whether or not the rule or in this case
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the law is being followed in this case
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72% of people correctly predicted that
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the cards beer and sex team must be
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turned over the beer card has to be
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turned over to make sure the person
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drinking it is old enough the water card
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is irrelevant since it doesn't matter
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what age the person is the 25 card is
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also irrelevant since it doesn't matter
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whether they're drinking alcohol or not
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since it over 18 and the 16 card must be
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turned over to make sure that person is
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not drinking alcohol it's much easier
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for us to reason and tasks like this
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because we can actually apply it to
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real-world scenarios in terms of actual
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variables this test is actually
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quantitatively identical to the first
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the statement if a person is drinking
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alcohol it must be 18 years or over it's
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just another F P then Q statement we're
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drinking alcohol at P and being 18 years
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or older as Q the four cards also
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represent the same four premises as
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before P naught P Q naught Hume this
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also helps highlight why certain
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inferences are illogical
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the most common wrong answer in the
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first task was the a in two cards but as
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stated earlier turning over the two card
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is illogical the two card is
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representing the premise Q and s real
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world example representing the Q premise
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as the h20 five card so it becomes more
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obvious why this is a logical just
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because a person is over 18 does not
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necessarily mean they're drinking
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alcohol so no matter what the drinking
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they're not breaking the law and
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therefore there's no need
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to turn over the card so the real P
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therefore Q cannot simply return R into
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Q therefore P as a personal drinking
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alcohol they must be 18 years old or
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cannot simply be turned right into F a
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person's over 18 they must be drinking
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alcohol this is n dot of reasoning and
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is therefore invalid it's worth pointing
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out though it's possible to be wrong
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using deductive reasoning and vice-versa
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is possible to arrive at correct
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conclusion using inductive reasoning
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deductive reasoning is only as correct
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as its premise so given an incorrect
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premise like all parts can fly we could
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use modus tollens to logically deduce
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that if it can't fly it's not a Bart
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this is obviously false because the
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penguin is a species of bird that can't
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fly and if we return to our Tiger
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example if we see a tiger and say it has
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stripes therefore as a tiger this is an
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invalid form of reasoning yet we have
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arrived at correct conclusion in fact
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inductive reasoning is actually
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incredibly useful and we use it on a
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daily basis with incredible accuracy
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some of the most obvious statements an
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assumption should we make are actually
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using inductive reasoning things as
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obvious as the Sun will rise tomorrow or
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if I drop a coin it will fall to the
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ground these statements though obvious
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are actually using inductive reasoning
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how do we really know the Sun will rise
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tomorrow because it's present every day
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of a life so far but nothing that has
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happened in the past can guarantee will
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happen in the future we can only make
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predictions and increase the certainty
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of our protections but we can never
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guarantee outcomes in fact everything we
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know about the universe we know through
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end up the reasoning how do you think we
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get these premises in the first place
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how do we know that all Tigers have
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stripes through inductive reasoning but
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there's no way to know for sure that all
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Tigers have stripes maybe there's an
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undiscovered species of tiger and a
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jungle somewhere with no stripes it's
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just that every tiger anyone has ever
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seen has had stripes so we can say with
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a high degree of confidence that all
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Tigers have stripes but it's impossible
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to know for sure in fact according to
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the strictest rules of logic it's
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impossible to know anything for sure
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through scientific research we can only
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increase the likelihood that something
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is true but can never actually confirm
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it famous philosophical quotes
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that nothing can be normed nor even this
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but just because something can be known
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with 100% certainty when all the
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scientific evidence points to something
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any rational person would accept it as
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fact so it comes to reasoning it's not
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just about logic but also a bit common
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sense and rationality - thanks for
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watching
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[Music]
