Introduction to Critical Thinking

Introduction to Critical Thinking Think Slowly Ask Questions Cultivate a Healthy Skepticism

Making Sense • Students often say things like “that makes sense”, and they conclude that what makes sense is thus true.

Truth and Making Sense • It is important to understand that: All that is true makes sense. but it does not follow that: All that makes sense is true

Critical Thinking All giraffes are animals. but it does not follow that: All animals are giraffes. Some animals are cats, dogs, humans, squirrels, etc.

The Dangers of Inferencing Would you agree with the following premise? If a student is lazy and does not care about school, then he will often be late for class?

Inferencing It’s actually true: If a student is lazy and cares little about school, we can reasonably expect that he will often be late for class. But does it follow that “if he is often late for class, then he is lazy and cares little about school”?

Inferencing No, it does not. Students typically understand that. Consider the following:

The dangers of inferencing • If a student is lazy and does not care about school, • If a student is feeling very sick and missed the bus as a result, • If a student’s bus was late, • If a student’s parents are always fighting and he’s feeling rather depressed and can’t get himself motivated, • If there was an accident on the road and roads were closed, • then he will be late for class

Inference The “if” clause is called the antecedent, the “then” clause is called the consequent: If you eat cake every day, then you will get fat. antecedent consequent

The dangers of inferencing • If a student is lazy and does not care about school, • If a student is feeling very sick and missed the bus as a result, • If a student’s bus was late, • If a student’s parents are always fighting and he’s feeling rather depressed and can’t get himself motivated, • If there was an accident on the road and roads were closed, As you can see, there are a number of possible antecedents that “make sense” out of the consequent. • then he will be late for class

Hypotheses • If ________________________________ , then he will be late for class An unknown antecedent is a “hypothesis” (a conjecture) There are any number of possible hypotheses that can explain the consequent.

Inference Mean Principal then he will have a very serious demeanor then he will have a very serious demeanor

The dangers of inferencing Notice how often we make inferences about people, like the school principal, a teacher, a person living on the street, etc. We settle upon the first hypothesis that “makes sense” (or the one that makes us feel better). • We forget that it is not necessarilythe case that if it makes sense, it is true.

Induction The process of going from the evidence (the consequent) to the hypothesis (antecedent) is called induction. The scientific method is inductive: If _______________ , then he will have a fever and be vomiting. The evidence or symptoms are in the ‘consequent’. The antecedent is any number of possible hypotheses (flu, another virus, food poisoning, poison, etc.).

Testing • That is why testing is so important in the sciences. • A hypothesis has to be tested and tested again, etc., before we assume it is true. • Keep in mind, however, that confirmation does not prove the hypothesis. We want to test in order to disconfirm the hypothesis: Try to figure out this rule: Click YouTube Video: https://www.youtube.com/watch?feature=player_embedded&v=vKA4w2O61Xo

Induction Biases and Fallacies • Confirmation bias • Availability Bias (WYSIATI) • Post hoc ergo propter hoc (confusing correlation with causation) • Round Trip Fallacy • Fallacy of Misplaced Authority • Ad Hominem • Narrative Fallacy and Selection Bias

Confirmation Bias Consider that if John killed his mother, then there will be evidence of a motive(i.e., life insurance policy). It was discovered that: • John was in debt and needed money to pay those debts. • his mother recently took out an accidental death insurance policy and named John as the beneficiary • John does not have an alibi for the time of the murder. • John owns a hunting knife (and his mother was stabbed to death). • Neighbors said that John and his mother were arguing on the day of her murder. All these facts “confirm” the hypothesis (conjecture) that he killed his mother. But this does not prove he did so. Investigators know this. So often it has happened that a prime suspect like John, who had all kinds of evidence against him, turned out to be innocent (DNA). What is needed at this point is more attention to possible evidence that disconfirmsor refutes the original hypothesis (conjecture). What often occurs, however, is that such evidence is overlooked, because it does not confirm our original hypothesis, and that can be a tiring thought (we’re back to the drawing board). Lazy investigators are dangerous!

Confirmation Bias The confirmation bias is the tendency to favorevidence that confirms our hypothesis. Those pieces of evidence stand outfor us (they seem right), precisely because they confirm our original hypothesis. But, confirmation does not prove a hypothesis. What a good scientist or investigator will do is seek out evidence that “disconfirms” a hypothesis, proving it is false. I.e., If the principal above has 6 kids at home, that is strong evidence that the hypothesis “he hates kids” is wrong.

The Murder of Dorothy Donovan A 70-year-old woman, Dorothy May Donovan, was found murdered in her home. She was stabbed to death. Nothing was missing from the home, and she had not been sexually assaulted. She has one son, Charles Holden, for whom she took out an insurance policy. He is the sole beneficiary. What can we infer from these facts? • She was killed by her son Charles (a factory worker), who had debts and needed the insurance money. • She was killed by someone hired by her son, Charles, who had debts and needed the insurance money. • She was killed by a perfect stranger (to both of them), an ex-con, who broke into the house because he needed a place to sleep, but when she confronted him, he killed her for fear that she could identify him, and he would be sent back to jail. • She was killed by someone about to rob the house, but when she woke up and came down and saw the man, she screamed and threatened to call the police, he panicked, stabbed her, and fled the scene without achieving his goal, which was to rob the house.

Donovan murder continued The police take Charles in for questioning. Here is his story: • At around midnight on June 22, 1991, he was leaving a Hardee’s restaurant when a man came to his truck, asking for a ride. The man said that his sister was having a baby and that he needed to get to the hospital. Charles told the police that at first, he told the black man that he could not give him a lift, because he wasn’t going very far—he only lived a few blocks away. But after some pressure, he changed his mind and gave the man a lift.

Donovan murder Shortly thereafter, Charles stopped at an intersection (in Delaware, just outside of Harrington). The hitchhiker got angry and started attacking him. Charles said he opened the door, got out and ran. The hitchhiker grabbed a screwdriver from the floor of the truck and ran after Charles, and the fight continued. So Charles stopped and agreed to take the man to where he wanted to go. But as the hitchhiker went around to the passenger side, Charles jumped in, locked the door, and drove off. The hitchhiker tried to run after him, but soon gave up.

Donovan murder Charles did not want to turn and proceed to his home, which was half a mile from where he left the man, in case the hitchhiker would see him and take revenge, so he continued to drive around. Finally, he returned to his trailer, but he noticed someone lurking around it; he looked like the hitchhiker. So he did not pull into the driveway. Instead, he called the police from a local pay phone. An officer came and went with him to his trailer and then his mother’s house, Dorothy Donovan, who lived in the house next to the trailer. They saw that the back door window had been broken and there was blood inside the house. They proceeded up the stairs to Dorothy's bedroom and found her lying dead; she’d been stabbed to death.

Facts in evidence: Nothing was stolen from the house, so this was not a robbery. It was not a sexual assault. Charles refused to take a polygraph. So what motive could anyone other than Charlie have for killing this woman? What is the likelihood that a hitchhiker would eventually turn down a street and find Charles’ mother’s house and kill her? Why would he do so? In revenge for not getting a lift farther up the road? And how would he know that this was Charles’ mother? The likelihood that he would find Charles’ house is very low; the probability that he would know that his mother lived in the house behind him is even lower. Moreover, Dorothy Donavan recently took out an accidental death insurance policy and Charles was the sole beneficiary, and he needed money to pay back certain debts that he had. And who likes living in a trailer when you can inherit a beautiful house upon the death of the owner? As you can see, there is a great deal that confirms the hypothesis that he is the killer.

How would you rate the likelihood that this story is the truth? On a scale of 1 – 10 (1 = highly unlikely; 10 = almost certainly true) 1 2 3 4 5 6 7 8 9 10

Donovan murder The police thought his story was ludicrous.

Conclusion • The forensic team found a bloody palm print on the stair railing. It did not match Charlie’s palm print. Witnesses at the Hardee’s confirmed that the hitchhiker did exist. The DNA evidence did not match Charles.Although the evidence is looking better for Charles, the narrative is still rather unbelievable (improbable). And so authorities began to speculate that perhaps Charles hired someone to kill his mother.

Solved • 15 years later, a DNA match surfaced. The killer was Gilbert Cannon of Delmar, MD. He was high on cocaine at the time, and he said that he went to that particular house because it was the first one he could find in which there appeared to be no one home. He was surprised to learn that this was the mother of the man who gave him a lift (Charles). • As you can see, what appears to be highly improbable (his story) may still turn out to be true. A theory with lots of evidence that confirms a hypothesis (that he is the killer is highly probable) may be false.

Availability Bias We have a tendency to make decisions and/or judgments on the basis of information that is readily available, all the while believing that this is all that is available (There is a bias in favor of readily available information). For example: Circle the number for that which you think (based on what you know) is the number one cause of death annually in the United States. • ___ AIDS • ___ Motor vehicle accidents • ___ Breast Cancer • ___ Medical mistakes • ___ Aviation • ___ Weapons related violence

Availability bias The answer is “medical mistakes”. • Most people would not put medical mistakes, because that information is not made available to us. What is made available is AIDS deaths, motor vehicle accidents, plane crashes, etc. • Bias in the media contributes to availability bias. There is so much that is not covered in the media for one reason or another that is far more important than what is typically covered.

WYSIATI WYSIATI is the acronym for What You See Is All There Is (Daniel Kahneman, Thinking Fast and Slow) Mr. Alphonso once told me that when he first came to Canada from India, he was expecting students to stand up as he entered the classroom; for teachers are highly esteemed in India. He was rather taken aback when he first walked in to a classroom here; students would be talking to one another and they would pay not the slightest attention to him. Like the rest of us, he was subject to an availability bias (What You See Is All There Is)

Availability bias What is the most popular snack in the world among teenagers? • Chocolate bars • Potato chips • Popcorn • Other

Availability Bias Ans: Other: rice. For the answer, we tend to look to what is immediately available to us, forgetting that there is so much we do not see (so much that is not available).

Availability Bias If you were to go to a movie depicting inner-city drug gangs and gang wars, violence, etc., and then were asked upon leaving the theatre whether gangs are becoming a serious problem in Toronto, you would probably answer ‘yes’, relying on the most available information, without making the effort to think through the question.

Fallacy of post hoc ergo propter hoc Assuming that when one event precedes another, it is the cause of the succeeding event. I was doing poorly in school, but then my grandmother gave me this pagan amulet to wear around my neck, and then my marks started to improve. I am convinced it works. I wear it all the time now.

Post hoc… John purchases a new laptop and it works fine for months. He then buys and installs new software. The next time he starts up his new laptop, it freezes. He concludes that the software is the cause of the malfunction.

Confusing correlation and causation “Every time my older brother eats sweets, it gives him acne. Thus, sweets cause acne” There might indeed be a correlation between those who have acne and those who eat sweets. But correlation is not necessarily causation.

Sweets and Acne Cause Effect But, because of that correlation, we are quick to assume that eating sweets is the cause of the acne.

However, it is possible that both are caused by some other factor, i.e., anxiety, stress. The stress at exam time causes a person to eat more sweets, and at the same time, the anxiety causes his or her acne to break out. The sweets are not necessarily the cause of the acne, although sweets and acne are correlated. Unknown cause (possible hypothesis)

Correlation and causation “The majority of prison inmates come from poor backgrounds. Therefore, poverty is the cause of crime”

Causation… This is a popular confusion of correlation and causation. Forensic psychologist Stanton Samenow points out that we must not overlook the very real possibility that those kids with anti-social personality are the cause of instability in their families and their parents’ marriages, which in turn can lead to divorce, then poverty, etc. Also, the correlation can easily be explained by reversing the terms: those who have a criminal personality do not want to work hard, are not responsible enough to hold down a steady job, they are unreliable, thus most often unemployed, thus living below the poverty line. There is no simple explanation

Round trip fallacy A common statistical error: #1: 99% of all terrorists are MuslimsAbdul is a Muslim.Therefore, Abdul is a terrorist. Or #2: 87% of oranges in this box are grade A.This orange is grade A.Therefore, this orange came from this box.

Explanation of #1 There are about 2 billion Muslims in a world of about 7 billion. Thus, about 30% of the world’s population are Muslims. There are about 10,000 terrorists in the world, 99% of whom—let’s assume—are Muslims. That gives us 9,900 terrorists who are Muslim, out of the 2 billion Muslims in the world. That’s: 9,900 2,000,000,000 It is highly improbable that Abdul is a terrorist. Or, 0.000495%

Explanation of #2 87% of oranges in this box are grade A. (There are 100 oranges in this box) But this orange in my hand is grade A. Can we conclude that it is from this box? There are billions and billions of grade A oranges in the world. What are the chances that this grade A orange is from this box of 100 oranges? 1 1000,000,000,000 Highly improbable.

However We can indeed argue the following statistical argument: 87% of oranges in this box are grade A.This orange is from this box.Therefore, this orange is grade A. (87% probability = high) Or, 95% of all Italians are Catholic.Luigi is Italian. Therefore, Luigi is Catholic (95% probability = high)

Catholic or Protestant World renowned golfer Rory McIlroy (winner of the 2014 British Open) is from Northern Ireland. Catholics make up a 40% minority in Northern Ireland. 60% of Northern Irish are non Catholic.McIlroy is Northern Irish. Therefore, McIlroy is non Catholic (60% probability that conclusion is true) From a statistical point of view, he is probably not a Catholic.

Rory McIlroy, it turns out, is Catholic Probable arguments are always uncertain

Fallacy of Misplaced Authority Consists of appealing to the testimony of an authority on an issue that is outside his or her proper field of competence (expertise). "My doctor assured me that Fords are the best cars. Therefore, I'm going to buy a Ford. After all, he is a doctor." Having a symposium with this year’s Nobel Prize winners in Chemistry, Physics, and Medicine in order that they may shed light on world issues and offer political solutions to the world's problems.

The Fallacy of ad hominem (to the man) This involves the criticism of some person's position or belief by criticizing the person rather than the position itself. I.e., • That man couldn’t be a good priest, just look at his belly. • He doesn’t know what he’s talking about. Just listen to his stuttering. • I’m not going to vote for him; I can’t stand the way he looks.

Ad Hominem How can this man possibly be right about the Theory of Relativity? Look at the way he combs his hair!

Ad Hominem Oh my G _ _ ! Look at his eyes! I’d vote for him over Harper any day!

Introduction to Critical Thinking