Abstract: People respond quickly when they have a clear preference and slowly when they are close to indifference. The question is whether others exploit this tendency to infer private information. In two-stage bargaining experiments, we observe that the speed with which buyers reject sellers’ offers decreases with the size of the foregone surplus. This should allow sellers to infer buyers’ values from response times, creating an incentive for buyers to manipulate their response times. We experimentally identify distinct conditions under which subjects do, and do not, exhibit such strategic behaviour. These results provide the first insight into the possible use of response time as a strategic variable.

Recent work has revealed that people are better at making decisions between high-value options than low-value options. One explanation for this puzzling result is that arousal increases when people expect to earn large rewards. Here, we test this hypothesis using two versions of the same color discrimination task with different incentives, one with fixed rewards (accuracy-based) and one with rewards that scale with value (value-based). Online data collection is ongoing; our target sample is n=30. We will use the drift-diffusion model (DDM) to study the relationship between accuracy and overall value. We hypothesize that there will be a positive relationship between option values and accuracy in the value-based condition, but not in the accuracy-based condition, as the fixed reward provides no incentive to respond more accurately to higher-value options. These results would indicate that value-based discrimination is primarily driven by goal-based factors.

Intertemporal choices - decisions that play out over time - pervade our life. Thus, how people make intertemporal choices is a fundamental question. Here, we investigate the role of attribute latency (the time between when people start to process different attributes) in shaping intertemporal preferences using five experiments with choices between smaller-sooner and larger-later rewards. In the first experiment, we identify attribute latencies using mouse-trajectories and find that they predict individual differences in choices, response times, and changes across time constraints. In the other four experiments we test the causal link from attribute latencies to choice, staggering the display of the attributes. This changes attribute latencies and intertemporal preferences. Displaying the amount information first makes people more patient, while displaying time information first does the opposite. These findings highlight the importance of intra-choice dynamics in shaping intertemporal choices and suggest that manipulating attribute latency may be a useful technique for nudging.

The drift diffusion model (DDM) is a prominent account of how people make decisions. Many of these decisions involve comparing two alternatives based on differences of perceived stimulus magnitudes, such as economic values. Here, we propose a consistent estimator for the parameters of a DDM in such cases. This estimator allows us to derive decision thresholds, drift rates, and subjective percepts (i.e., utilities in economic choice) directly from the experimental data. This eliminates the need to measure these values separately or to assume specific functional forms for them. Our method also allows one to predict drift rates for comparisons that did not occur in the dataset. We apply the method to two datasets, one comparing probabilities of earning a fixed reward and one comparing objects of variable reward value. Our analysis indicates that both datasets conform well to the DDM. We find that utilities are linear in probability and slightly convex in reward.

When people make choices, the items they consider are often embedded in a context (of other items). How this context affects the valuation of the specific item is an important question. High-value context might make items appear less attractive because of contrast-the tendency to normalize perception of an object relative to its background-or more attractive because of assimilation-the tendency to group objects together. Alternatively, a high-value context might increase prior expectations about the item's value. Here, we investigated these possibilities. We examined how unavailable context items affect choices between two target items, as well as the willingness-to-pay for single targets. Participants viewed sets of three items for several seconds before the target(s) were highlighted. In both tasks, we found a significant assimilation-like effect where participants were more likely to choose or place a higher value on a target when it was surrounded by higher-value context. However, these context effects were only significant for participants' fastest choices. Using variants of a drift-diffusion model, we established that the unavailable context shifted participants' prior expectations towards the average values of the sets but had an inconclusive effect on their evaluations of the targets during the decision (i.e. drift rates). In summary, we find that people use context to inform their initial valuations. This can improve efficiency by allowing people to get a head start on their decision. However, it also means that the valuation of an item can change depending on the context.