CGSC 2001 Lecture Notes - Lecture 14: Recognition Heuristic, Availability Heuristic, Representativeness Heuristic

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COGSCI March 31, 2015
Rationality and Fast-and-Frugal
Heuristics
Example
Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a
student, she was deeply concerned with issues of discrimination and social justice, and also
participated in antinuclear demonstrations. Which is the most likely alternative?
oLinda is a bank teller
oLinda is a bank teller and is active in the feminist movement
Representativeness Heuristic
Majority of people choose B – not the correct answer, actually the least likely choice
One of the heuristics people use when making judgments about the probability of an “event”
under uncertainty is called the representativeness heuristic
oEvaluate probabilities based on how similar two elements are to one another
In the example above, option “B” is more similar to the description of Linda than
option “A”, so we incorrectly choose it
oWhy is B the wrong answer?
The probability of a conjunction (a combination of elements) is never greater
than the probability of its individual elements
Example:
Which is a more likely cause of death: being killed by falling airplane parts or by a shark?
Availability Heuristic
Most people rate shark attacks as the more likely answer, but this is not correct
oWhy is this the more common answer?
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COGSCI March 31, 2015
oShark attacks receive more publicity than falling airplane parts and so are more likely to
be stored in memory
The more repeated fact is the more likely to be remembered
Tversky calls this the availability heuristic
oWhatever first comes to mind is likely to be right
o“if you can think of it, it must be important”
Rationality
Rationality: refers to ability to make judgment and choose courses of action under conditions of
uncertainty
The last two cases illustrated examples of judgment not based on rules of probability
Three Views of Rationality
1. Unbounded rationality
a. When making a decision, the individual has unlimited knowledge, computational power,
and time to make the decision
a.i. Linda the bank teller example: obtain the decision using law of probability
b. When making a decision when there is uncertainly and user preferences, ALL THE
POSSIBLE ALTERNATIVES are considered, taking into account two things:
b.i. How likely something is to happen (probabilities)
b.ii. How desirable that outcome is (utilities)
b.ii.1. Why both? Let’s say that you really want an iPhone, but would
settle for a Samsung phone. There are two raffles: Raffle A gives you a
75% chance of getting a Samsung; Raffle B lets you win an iPhone with a
5% chance. You can only play in one of these. Which do you choose?
c. Issues:
c.i. Often takes way too long to explore all possible alternatives
c.ii. People just don’t think this way in many instances
2. Contextualized rationality
a. Trying all possible alternatives (unbounded rationality) is too expensive
b. Proposal: try only some of the alternatives and stop when considering the remaining
ones are not worth it
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