In our daily lives, we often take sequential actions rather than making single, isolated decisions. A typical example is deciding which items we want to put in our shopping basket. Previous studies have investigated the temporal dynamics of these sequential decisions using a virtual shopping paradigm (Wolf et al., 2018, 2019, Front. Psychol.; Xu et al., 2023, Front. Psychol.). Specifically, these studies have examined the probability of accepting or rejecting different food items as well as the speed of those dietary decisions with various constraints. However, the cognitive mechanisms of the underlying sequential decision dynamics have not been addressed.
Here, we replicate and extend the study by Xu et al. (2023) using their paradigm in an online study, in which n = 100 participants decided for sequentially encountered items whether or not to add them into their shopping basket. In one condition, participants could also defer the choice. The number of food items that could be added to the basket was manipulated between subjects.
To elucidate the cognitive mechanisms, we evaluate various evidence-accumulation models that are specifically tailored to sequential decision problems, testing how well they can provide a comprehensive account of the reported choice and response time patterns. Simulations with these models suggest a pivotal role of the starting point of evidence accumulation, which is biased towards reject decisions. This allows to explain why reject decisions are faster than accept decisions, and why this difference is modulated by the size of the shopping basket.