Ambiguity in risky versus intertemporal choice: Unique and shared neurocognitive aspects

Description: People often choose between rewards that differ in their outcome probability (risky choices) or delay (intertemporal choices). Importantly, we are typically unaware of the precise probabilities or delays involved, referred to as probability- and time-ambiguity, respectively. Despite the ubiquitousness of ambiguity in real-life, our understanding of the involved processes is limited. Using preregistered analyses, this study compared behavioral and neural ambiguity effects across the probability and delay domain. While undergoing MRI, participants (N=80) repeatedly made choices between a fixed sure option today and a variable option (VO) that varied across trials in its gain amount and -critically- in its exact win probability, its exact delay, its probability-ambiguity level, or its time-ambiguity level. As expected, fewer VO choices were made for smaller win probabilities, longer delays, and higher probability- and time-ambiguity levels. The effects of probability- and time-ambiguity on choice were trend-correlated. Neurally, we found domain-general ambiguity-related increases in bilateral PPC and dlPFC activation, likely indicating that dealing with ambiguity is more complex, thus requiring more domain-general executive control. Domain-specific ambiguity effects were only found in the parametric analyses: Bilateral IPS, IPL, and the precuneus responded more strongly to increases in ambiguous than exact delays, whereas activation for variation in ambiguous versus exact probabilities did not differ. These findings fit theoretical notions that time-ambiguity may require more prospection-related processes than exact delays, while prospection may be similarly irrelevant across exact and ambiguous probabilities. Thus, ambiguity may increase the complexity of decisions, which gets implemented in both a domain-general and domain-specific manner.