A Brain Imaging Study of Procedural Choice

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A Brain Imaging Study of Procedural Choice

• Aldo Rustichini, John Dickhaut, Paolo Ghirardato,
  Kip Smith and Jose Pardo

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Outline of talk

• What is the issue being addressed?
• What claims do we make?
• What is the design of the study?
• What does the data with risky reference gambles
  show?
• What does the data with certainty reference
  gambles show?
• What do we conclude?

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What issues are addressed?

• What is the procedure that is followed when
  choices are made?
• How do subjects respond differently to different
  degrees of ambiguity?
• Can we distinguish strategies based on cognitive
  considerations?
• How do we understand the relationship between
  these types of choices and emotions?

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What claims do we make?

• If we isolate choice from learning and
  incremental feedback, then the choice process is
  guided by evaluation of the options.
• The evaluation involves areas of the brain used
  in approximate computation not used in language.
• Subjects face ambiguity as a computational
  problem.
• In this problem Partial Ambiguity is
  qualitatively different from Risk and from
  Ambiguity and this fact appears in brain
  activity.

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What is the design?

• Types of gambles.
• Types of choices faced by subjects and
  conditions.
• Details of design.
• A description of the procedure.

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Types of Gambles
Ambiguous Gamble
Partially Ambiguous Gamble
Risky Gamble
Certainty
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Types of Choices Made By Subjects
Example of an Ambiguous-Certain (AC) Gamble
Conditions in the experiment
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Details of design

• 96 choices (3 times 15 R choices for the
  reference lottery and 3 times 17 for the C
  reference lottery.)
• Eight seconds per choice.
• Payments at end of experiment.
• 4 of the 96 lotteries randomly chosen.
• Each of these 4 would be implemented by the draw
  of a ball from an appropriately filled urn.

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Description of Procedure
Blood Flow Increases in Areas Where Neurons Fire
Task leads To Neuronal Firing
Subject Supine
IV 015 Water
Positrons are Emitted from Bloodstream
Torus Collects Positron Counts
Region of Neuronal Firing Inferred
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Results

• Risky Reference Lottery
• Choice Data
• Response Times
• Imaging Data

• Certainty Reference Lottery
• Choice Data
• Response Times
• Imaging Data

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Risky Reference Lottery
Choice Data
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Risky Reference Lottery
Response Times
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Risky Reference Lottery
Brain Imaging
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Certainty Reference Lottery
Choice Data
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Certainty Reference Lottery
Response Times
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Certainty Reference Lottery
Brain Imaging
Superior frontal gyrus-frontal lobe
Parietal Activation
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Conclusions

• The rresponse times and brain imaging support the
  proposition that there are different processing
  procedures for risky and certain reference
  gambles.
• Risky gambles are processed based on the safety
  of the gambles.
• With certainty gambles subjects employ a cutoff
  strategy.
• Neither response time nor brain imaging further
  differentiate what happens in different
  conditions with risky gambles.
• On the other hand we are able to establish that
  certainty gambles appear to be operating on an
  approximation basis - this is partially
  corroborated by the fact that when subjects
  process choice with the certainty gamble closer
  to the cutoff that it takes more time to process.
• Brain imaging gives us both support for the idea
  that approximations are used and furthermore
  provides insight into difference within
  conditions for the certainty comparison gamble.

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• Neither response time nor brain imaging further
• differentiate what happens in different
  conditions with
• risky gambles.
• On the other hand we are able to establish that
• certainty gambles appear to be operating on an
• approximation basis - this is partially
  corroborated by
• the fact that when subjects process choice with
  the certainty
• gamble closer to the cutoff that it takes more
  time to process.
• Brain imaging gives us both support for the idea
  that
• approximations are used and furthermore provides
  insight
• into difference within conditions for the
  certainty comparison
• gamble.