13' The Role of Chance in Psychology

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13. The Role of Chance in Psychology

• Stanovich
• Chapter 11

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But Before that . . .
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More on Probability

• Remember, that human beings are not very good at
  probabilistic reasoning.
• There are many reasoning fallacies that get in
  the way of our making accurate judgments.

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Lets Make a Deal

• Classic television game show from the 1960s and
  70s.

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The 3 doors

• Theres a new car behind one door.
• Two pack mules behind the others.
• First, pick a door.
• Then, Monty shows whats behind a door not
  pickedalways a mule.

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Now the real choice

• Stick with the original choice or switch?
• What are the odds?
• 50-50? . . ?

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The Solution

• http//www.stat.tamu.edu/west/applets/LetsMakeaDe
  al.html

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On to the role of chance . . .
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Why Do We Seek Out Patterns In Life?

• Humans feel a strong need to make order out of
  chaos

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Seinfeld

• The Statue
• big coincidences and little coincidences
• The Opposite
• You see how it all evens out for me?

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Randomly generated shapes are given structure

• Rorscach test
• Stanovich strongly in the anti-inkblot camp
• There are actually certain times when this test
  is useful.
• Interpretation is based on empirical data.
• Rorschach test evaluated in the context of other
  tests too.

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More shapes

• What do you see?

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More shapes

• What do you see?

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More shapes

• What do you see?

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More shapes

• What do you see?
• People like to see a pattern / impose structure.

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Conspiracy theories

• Layers layers of explanations to explain
  randomness

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Top Ten Conspiracy Theories of 2002, by Mike
Ward, www.alternet.org

• For about thirty minutes after his chief of
  staff told him that America was under attack,
  George W. Bush continued to sit in an elementary
  school classroom listening to a second-grader
  tell a story about a pet goat. He did a marvelous
  job of looking completely unsurprised. Meanwhile,
  four hijacked jumbo jets were able to fly
  off-course across several states without
  encountering any opposition from the most
  powerful and responsive air force in the world.
• Less than a month later, on the pretext of
  pursuing terrorist mastermind Osama bin Laden,
  the Bush administration began what it called a
  "war" on the impoverished and already war-torn
  country of Afghanistan. It turns out this assault
  had been in the works well before September 11
  took place. . .

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The Illusion of Control

• Lottery tickets
• Do you pick your own numbers?
• Lottery popularity dramatically increased when
  people were allowed to pick their numbers
• If subjects picked their own tickets, they wanted
  4x as much money to sell them back
• Just-World Hypothesis
• People get what they deserve

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Accept Error to Reduce Error

• 70 red light 30 blue light
• If guess red in all 100 trials you will be
  correct 70
• If guessed red 70 and blue 30 in 100 trials
• 70 trials will be red, you will be correct
  .70x7049 times
• 30 trials will be blue, you will be correct
  .30x309
• On all 100 trials, you are correct 58 times
• 58 vs 70 (Neither is 100 accurate but 70 is
  better)

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Clinical vs Actuarial Prediction

• Clinical predictions are not as accurate as
  actuarial predictions
• Even when
• The clinician has all the information that goes
  into the actuarial equation
• The clinician has extra information
• The clinician has equation and is asked to modify
  the prediction (actually clinician increases
  error)

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Does it always matter?

• Psychologists and psychiatrists write reports and
  testify in court about offenders
• The court wants to know can the person benefit
  from rehabilitation? What would help them? Are
  they at risk to re-offend?
• Forensic Psychologists do in fact use actuarial
  measures of general criminal recidivism, risk of
  violence, risk of sexual violence, etc. AND
  clinical judgment

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Should we do this?

• Debate.
• What do you think?
• Explain why.