Reasoning & Decision Making (Part 1) PDF

Reasoning & Decision Making Contents: (part 1) Reasoning – definition Deductive Reasoning...

Reasoning & Decision Making Contents: (part 1) Reasoning – definition Deductive Reasoning Thinking categorically Thinking conditionally Inductive Reasoning Four Types of Heuristics that cause errors in Reasoning KMF 1023 Availability Heuristic, Illusory correlations, Representative Heuristic & COGNITIVE PSYCHOLOGY Confirmation bias Decision Making Lecturer: Norehan Zulkiply The utility approach FSKPM, Universiti Malaysia Sarawak Reasoning & the Brain Reasoning Decision Making Reasoning Cognitive processes by which Making choices between alternatives people start with information and come to conclusions that go beyond original Eg. Buying an apartment, buying the perfect information ice cream, gambling E.g. Heuristics in perception, Memory Can involve both deductive and inductive construction reasoning Two types of Reasoning Deductive: a conclusion logically follows from premises Inductive: arrive at conclusions that are probably true, based on evidence Deductive Reasoning Deductive Reasoning Basic form of deductive reasoning: Syllogisms (general to specific) Syllogism = 2 statements called premises followed by third statement called conclusion Categorical Syllogism Conditional Syllogism 1  Deductive Reasoning (categorical syllogisms) Categorical Syllogisms Eg. -Has 2 premises and 1 Two approaches to study categorical conclusion. syllogisms: Premises: Normative approach- indicate which forms of All As are Bs -Premises & Conclusion syllogisms are valid and which are not (uses logic describe the relation thinking) All Bs are Cs between 2 categories by using statements that begin Conclusion: with some, no, or all Descriptive approach – how well people can All As are Cs evaluate whether a syllogism is valid (uses -Syllogism is valid if psychology) conclusion follows logically from its two premises Normative Approach Normative approach premise 1:All As are Bs 2 main principles: premise 2:All Bs are Cs Principle 1: If the premises are true, the conclusion of a valid syllogism must be true Conclusion: All As are Cs premise 1: All As are Bs True Although artificial, provides a good way premise 2: All Bs are Cs True of testing how well people are at Conclusion: All As are Cs True determining validity This is valid because the conclusion logically follows from the premises Normative approach Descriptive Approach Principle 2: The validity of a syllogism is The normative specifies the correct answers determined only by its form, not its content The descriptive approach is concerned with Syllogism 1 Syllogism 2 how well people can actually judge validity of a syllogism (uses psychology) premise 1: All As are Bs All Birds are Ants premise 2: All Bs are Cs All Ants have 4 legs So syllogism 2 is not valid if it is determined -------------------------------- -------------------------------- further by Descriptive approach. Conclusion: All As are Cs Conclusion: All Birds have 4 legs Question :So how do we determine further it’s validity? 2 Sources of error in syllogism Atmosphere Effect: qualifiers (all, some, no) create People make errors in syllogisms. an overall mood that influences the evaluation/production of the conclusion Two common source of errors Two All’s generally suggests an All conclusion (Syllogism 1 Atmosphere effect in your textbook) One or two No’s suggest a No conclusion Belief bias One or two Some’s suggest a Some conclusion (Syllogism 4 in your textbook) All of the students are tired Some tired people are irritable Some of the students are irritable  This syllogism is invalid if it is judged using descriptive approach. The truth of the conclusion can be argued) However….Atmosphere effect would lead to us to say that this invalid syllogism is valid. Deductive Reasoning (thinking conditionally) Belief Bias: if a syllogism’s conclusion is true or Conditional Syllogisms: agrees with a person’s beliefs the syllogism will be Have two premises and a conclusion too…but judged as valid the first premise has the form “If…..then..” All of the students are tired Some tired people are irritable Eg. Some of the students are irritable (believable) Premise 1: If I study smart for KMF 1023 mid term exam, then I will get a good grade Premise 2: I studied smart for the KMF 1023 mid- It seems possible that “Some of the students are term irritable” (could be true) Conclusion: I got a good grade So if the syllogism’s conclusion is parallel with your belief ….then you will judge it as valid. This type of deductive reasoning is common in everyday life Basic type of conditional syllogisms Deductive Reasoning First Premise: If I study (p) then I’ll get a good grade (q), is the same in all four cases Types of Conditional Syllogisms No. Second premise Conclusion Type Valid? %Correct p = antecedent (‘if’) 1. p Therefore q affirming the antecedent (modus ponens) Yes 97% q = consequent (‘then’) I study Therefore, I’ll get a good P is affirmed grade  If p..then q 2. Not q Therefore, not p Denying the consequent Yes 60% (modus tollens) I didn’t get a Therefore, I didn’t study q is negated good grade 3. Q Therefore p Affirming the consequent No 40% “If I don’t submit my assignment on time I got a good Therefore, I studied then my marks will be deducted. ” q is affirmed grade 4. Not p Therefore not q Denying the antecedent No 40% I didn’t study Therefore, I didn’t get a p is negated good grade Source: from Evans et al., 1993 3  Reasoning & Decision Making (part 2) Deductive reasoning – moving from general to specific (reach to a conclusion that is logically follows from premises) Inductive reasoning – moving from specific to general (arrive at a conclusion that is probably true, based on evidence) Inductive Reasoning Make a conclusion based on evidences (observations) Inductive reasoning Premises are based on observation of one or more specific (Specific to general) cases Generalize from cases to a more general conclusion In deductive reasoning, premise is stated as a fact. In inductive reasoning, premises are based on observation(s). Consider this arguments Observation: There are lots of vultures overhead, I’m in a desert with no water, Conclusion : I’m pretty sure they’re waiting for me to die. Inductive Reasoning Another example: Deductive reasoning = validity of syllogism Observations: There are lots of students in the cafeteria in the afternoon, I saw some students eat Inductive reasoning = strength of hungrily, and the waiters are walking back arguments and forth to serve the ordered foods to the students Conclusion : I’m pretty sure that these students are really hungry. 4  Inductive vs. Deductive Reasoning -- Inductive Reasoning Fundamental Difference Criteria for inductive reasoning: Deductive reasoning is dependent on its premises Through pure logic, the conclusion is derived based on a Number of observations: I’ve often seen few premises vultures circling above thirsty people wandering deserts in old movies... Representativeness of observations: All the Inductive reasoning creates laws based on the vultures I know of are scavengers, and I’m observation of the facts to be scavenged... The premises of an argument are believed to support the conclusion but do not ensure it. Quality of evidence: It is statistically unlikely I’ll survive in a desert without water... Inductive Reasoning Inductive Reasoning Inductive reasoning used in Science & Four Types of Heuristics that cause everyday life errors in Reasoning: Basic procedure for making discoveries 1. Availability Heuristic used in generalization of results Illusory correlations 2. Simple assurance 3. Representative Heuristic Economical (identify certain trends) Conjunction Rule 4. Confirmation bias Inductive Reasoning 1. Availability Heuristic Heuristics: Tversky & Kahneman’s (1973) study: Which is more common: words beginning with r or ‘computational short-cut’ that saves us words with r as the third letter? time and is easy to use and results in correct answers most of the time but not Results: People tend to say words beginning all the time with r But There are 3x more r s in third position Things that are more easily remembered are judged to be more common 5  2. Illusory correlations 3. Representative Heuristic Illusory correlation – occurs when a correlation between two Representative Heuristic – occurs when people make events appears to exist, but in reality the correlation actually judgements based on how much one event resembles does not (or is much weaker than you assume it to be) another event Eg. Stereotypes (oversimplied generalization about a group of The probability that an event A comes from class B can be determined by how well A resembles the properties of class B. people that often focuses on the negative) All effeminate men are homosexuals All Asians cannot speak English Consider this example: All coloured people are stupid Robert is a male in the US, wears glasses, speaks quietly, and reads a All chinese are businessmen lot. Which is more likely? Robert is a librarian or Robert is a farmer? Results: people tend to choose librarian as Robert match people’s can occur when we expect two things to be related, so we fool idea of a typical librarian ourselves into thinking they are related even when they are not Why? Because they are influenced by the representative heuristic and base their judgment on how closely Robert’s characteristics (A) match those of a typical librarian (B) Representative Heuristic Representative Heuristic The likelihood that event A comes from class B depends on how close A resembles or represents B In a group of 100 people, there are But this means they ignore another important source 70 lawyers and 30 engineers. If Jack is picked of information – base rates randomly from that group, what is the chance Base rates – relative proportion of different classes that he is an engineer? of population In this example of Robert, statistically there were Results: people will pick the correct answer more male farmers than male librarians in the US, so when base rates such as the above are given this base rate shows that it is more likely that Robert is a farmer Representative Heuristic Representative Heuristic For some of the participants, this description is added.. People disregard base rate information Jack is a 45-year-old man. He is married and has 4 children. He is when they are given descriptive generally conservative, careful, and ambitious. He shows no information interest in political and social issues and spends most of his free time on his many hobbies, which include home carpentry, sailing, In many cases often this cause errors in and mathematical puzzles. reasoning. Is Jack more likely to be an engineer or a lawyer? People tend to choose engineer even when the earlier base rate shows 30% of chance that he is an engineer When the descriptive info. is given, participants increase their estimate that Jack is an engineer. They disregard base rate (in fact, only 30% chance of picking Jack as an engineer). 6  Representative Heuristic Representative Heuristic Another example: The correct answer is A but 85 % of Linda is 31-years-old, single, outspoken, and very bright. She majored in philosophy. As a student, she participants chose B because they were was deeply concerned with issues of discrimination and influenced by the representative social justice, and also participated in antinuclear heuristic. demonstrations. Linda’s description fits people’s idea of a typical feminist Which of the following alternatives is more likely to describe Linda? But in doing so they have violated the A) Linda is a bank teller Conjunction rule B) Linda is a bank teller and is active in the feminist movement Conjunction Rule Representative Heuristic P(A&B) P(A) By using the representative heuristic people incorrectly estimate the probability of an The probability of a conjunction of two events (A and event occurring based on the extent the B) cannot be higher than the probability of the event is a representative of a particular single event (A alone or B alone). category There are fewer feminist bank tellers than bank tellers Bank teller (A) Feminist & bank teller (A&B) 4. Confirmation Bias Confirmation bias - our tendency to selectively look for information that conforms to our hypothesis Decision Making Lord and coworkers ( 1979)- He identified one group of participants in favor of capital punishment, and another group against it. Then he presented the participants with descriptions of research studies on capital punishment (some showed a deterrent effect on murder, others provided no deterrent effect) Participants reaction on the studies reflected the attitudes they had at the beginning of the experiment. 7 Decision Making Decision Making Making choices between alternatives The Utility Approach Utility = useful or profitable Eg. Making decision to ensure the outcome will benefit Buying an apartment you the most or will be most useful or profitable to Choosing the “right” university for your you Economics utility theory undergraduate studies People are basically rational, so if they have all of the relevant Deciding which job offers you would want information, they will make a decision which results in the maximum expected utility to accept. Decision based on monetary value However, in reality people do not always make decisions that maximize their monetary outcome. Not because they are irrational, but they find value in things other than money Decision Making Reasoning & the Brain Decision based on monetary value Prefrontal Cortex (PFC): important The realities: Casinos- people still gamble even though it may in reasoning, problem solving & working not get them rich just for the fun of it memory Some outcomes cannot be calculated- people do not necessarily act to maximize monetary value, eg. Paying expensive airfare to go home to see a loved one Incorrect mental simulations – models that people create about what will happen based on decisions that they make, eg attending a particular university, winning the lottery Summary Summary Inductive vs Deductive Reasoning 1. Availability Heuristic Inductive – based on the strength of 2. Illusory correlations your argument (specific to general) 3. Representative Heuristic Conjunction Rule 4 types of heuristics that cause errors in 4. Confirmation bias inductive reasoning: 8 Summary Decision making based on the utility approach- make decisions in terms of monetary gain But there are problems with this approach Reasoning and decision making abilities – prefrontal cortex of the brain 9