A Tale of Two Systems: The effects of executive function on UG Decisions Aaron Tesch
Rational Theories Of Decision-Making • Plato: The spirit world is rational but our decisions are contaminated by the physical world. • Stoics believed they needed to purge the emotional contamination to find truth. I reject your offer !
Utility Theories Absolute value ≠ Utility : St. Petersburg Paradox Utility can't be calculated because of limitations of human cognition, therefore we use heuristics and have psychological biases. However, still used in much of economic theory.
Emotional Theories • Freud's Id • Sex sells • Behavior is not always rational
Two-System Decision Models <ul><li>Posner & Snyder (1975) and Schneider & Shiffrin, (1977) proposed two-systems models that pit a automatic system against a controlled system. </li></ul><ul><li>Kahneman (2003) outlined such a theory: </li></ul><ul><li>System 1 which automatically makes quick judgments based on simple heuristics and emotions </li></ul><ul><li>System 2 which monitors the quality of the answer System1 produced and corrects it if necessary. </li></ul>
Neural Evidence for Two-System Decision models <ul><li>Delay Discounting (McClure) </li></ul><ul><li>Moral Decision Making (Greene) </li></ul><ul><li>Ultimatum game (Sanfey) </li></ul>
Other Two-System Models? <ul><li>High vs. Low road visual processing </li></ul><ul><li>- Ahh a bug! </li></ul><ul><li>Facial Expression </li></ul><ul><li>- Say “monkey butts” </li></ul><ul><li>How do these systems relate to the decision systems? </li></ul>
Possible Neurological Evidence for Two system model in the UG <ul><li>• Sanfey (2003) had people play the responder in a series of Ultimatum Games. Found higher activation in dlPFC than the Insula when accepting unfair offers and higher activation in the Insula when rejecting offers. </li></ul>
Priming Affective systems <ul><li>• Harle & Sanfey (2007) found that rejection rates are reduced when primed with “sad” movie clips. </li></ul><ul><li>• Sadness = Insula activation? </li></ul><ul><li>• Also disgusting clips may increase rejection rates! </li></ul>
TMS on the DLPFC <ul><li>Van ‘t Wout et al. (2005) and Knoch et al. (2006) both showed that TMS on the DLPFC increases acceptance rates during the Ultimatum Game. </li></ul><ul><li>This suggests that the DLPFC is somehow, causally linked to decisions during the ultimatum game. </li></ul>
Working Memory is Associated with the DLPFC <ul><li>Sakai, Rowe, & Passingham (2002) found that there was activation of DLPFC during correct working memory trials but not for incorrect working memory trials. </li></ul>
Pilot Experiment (WM-Easy) <ul><li>Two groups were given a UG task either with a working memory prime or without. </li></ul>
Results of Acceptance Rate Analysis • Acceptance rates in the easy working memory task were significantly higher then the control group with no working memory prime. • There was also a significant interaction. Acceptance rates also decayed slower in the working memory condition then in the control condition.
Pilot Experiment (WM-Hard) <ul><li>A harder working memory task that varied color, shape and location dimensions was used instead of the simple black dot task. </li></ul>
r=-0.44* Results of Acceptance Rate Analysis • Acceptance rates are positively correlated with memory performance. i.e. they were negatively correlated with memory error rates as shown to the right.
Trial by Trial Analysis <ul><li>A chi^2 showed that participants were more likely to reject on incorrect trials then on correct trials. </li></ul>
Limitations <ul><li>Is loading the controlled system activating or depressing its function? </li></ul><ul><li>Are their affective confounds due to memory task feedback? </li></ul>
Limitations cont. <ul><li>• How general is the System 2? Is it a general executive functioning system, general working memory system, or is it limited to spatial working memory? We are not sure how the differences in memory task difficulty affect acceptance rates. </li></ul>
Experiment 1 <ul><li>• Independent measures of spatial working memory (Visual Digit Span), verbal working memory (N-back), switching (Global-Local), inhibition (SSRT) and self reported general executive function (BADS). </li></ul><ul><li>Also find the effect of different working memory difficulty levels on decisions within subjects. </li></ul><ul><li>The No Feedback condition also allowed detection of emotional feedback confounds. </li></ul>
Visual Digit Span Task <ul><li>• Adapted a digit span task to present 2-6 dots in a 3x3 grid instead of digits 1-9. </li></ul><ul><li>• Example with three dots -> </li></ul>
Ultimatum Game Trial <ul><li>Picture -> Proposal -> Decision -> Outcome </li></ul>R T Y F G H V B N
Type of Trials <ul><li>• Each participant received every combination of the five memory difficulty levels (2-6 dots) and the five UG Offer levels ($ 1-5). </li></ul>D,O 2 3 4 5 6 1 2,1 3,1 4,1 5,1 6,1 2 2,2 3,2 4,2 5,2 6,2 3 2,3 3,3 4,3 5,3 6,3 4 2,4 3,4 4,4 5,4 6,4 5 2,5 3,5 4,5 5,5 6,5
Outcomes <ul><li>• Updating but not switching or inhibition measures of EF have positive relationship with System 2 decision making system. </li></ul><ul><li>• There is no within subject effects of working memory difficulty level. </li></ul><ul><li>• The trend for a relationship for visual digit span performance is dependent on memory feedback. </li></ul>
Experiment 2: Affective Processing due to unfair feedback <ul><li>Unfair memory feedback </li></ul>Feedback R T Y F G H V B N
Outcomes <ul><li>• Relationship between visual digit span reversed. Suggesting an emotional prime in proportion of unfairness experienced. </li></ul>
Experiment 3: Priming vs. Loading <ul><li>Is there any differences in UG decisions or EF relationships with those decisions after priming vs. loading the working memory system? </li></ul>
Condition Timelines <ul><li>Condition WM Presentation Loaded task WM Test Unloaded task </li></ul><ul><li>Loading condition Dot Presentation -> UG Trial -> Dot Test -> Control </li></ul><ul><li>Priming condition Dot Presentation -> Control -> Dot Test -> UG Trial </li></ul>Loading condition Priming condition
Outcomes <ul><li>• The relationships between Updating and UG decisions that were not found in the other experiments were not found in the Priming condition. </li></ul><ul><li>• However, these relationships were not found in Loading control task either suggesting that the relationships mentioned above are fragile. </li></ul>
Overall Outcomes <ul><li>• No System 2 effects of memory difficulty in the within subject paradigm but evidence of a good range of memory task difficulty. </li></ul><ul><li>• Fragile relationship between independent updating measures and UG decisions. </li></ul>
Discussion <ul><li>• Little evidence supporting the connection of EF and System 2 decisions may suggest many interacting systems. </li></ul><ul><li>• However these results may simply be a limitation of the within subject paradigm. </li></ul>
Future Directions <ul><li>• Between subject memory manipulations. </li></ul><ul><li>• How are decision related System 1 and System 2 related to other similar cognitive systems i.e. visual systems and expression systems? </li></ul><ul><li>• What are the outlines of the systems related to decision making? </li></ul><ul><li>• Can these models help explain preference reversals? </li></ul>
Future Directions Cont. <ul><li>• Other paradigms? </li></ul><ul><li>• Online gaming e.g. Mafia Wars (5Million+), Vampire Wars, Kingdoms of Camelot etc. </li></ul>
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