The Role of Time Ambiguity in Intertemporal Choice: an fMRI study
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2015-08-21
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en
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Abstract
In intertemporal choices, people need to make tradeoffs between outcomes occurring
at different points in time. For example, we may be faced with the choice between
having a cake now (a sooner-smaller or SS reward) or having a slim figure later (a
later-larger or LL reward). In the real world, people often have imprecise information
about the timing of outcomes when making intertemporal choices (e.g., when exactly
does one have that slim figure?), which we call time ambiguity. However, how time
ambiguity influences intertemporal choices and how this is represented in the brain
has not been investigated before. Therefore, we developed a new intertemporal choice
task that systematically varies time ambiguity. Trials presented either exact outcome
timing (e.g., 5 weeks from now), or imprecise outcome timing in a range of weeks
(e.g., 3 to 7 weeks from now). Time ambiguity was either 4 or 8 weeks, added to the
SS reward, the LL reward, or to both. These 6 trial types were compared with standard
intertemporal choice trials without time ambiguity (i.e., with precise outcome timing
information). As expected, adding time ambiguity to an option made it less likely for
subjects to choose it. Whether time ambiguity was 4 or 8 weeks did not matter.
Neurally, we found significant ambiguity-related increases in activation in the
precuneus, PPC, MTG, dlPFC, SFG, IFG, MFG, cuneus, cingulate gyrus, and
midbrain (although not all of these clusters survived multiple comparison corrections).
Some – but not all – of these regions have previously found to be activated during
probability ambiguity, suggesting a partly shared and partly unique mechanism for
time ambiguity.
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Faculteit der Sociale Wetenschappen