The Role of Time Ambiguity in Intertemporal Choice: an fMRI study

Ikink, Iris

The Role of Time Ambiguity in Intertemporal Choice: an fMRI study

Files

Final_version_master_thesis_Iris_Ikink_2015.pdf (805.88 KB)

Authors

Ikink, Iris

Issue Date

2015-08-21

Language

en

URI

http://theses.ubn.ru.nl/handle/123456789/4121

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.