Figure 1.

Model and experiment. (A) Model. A relative decision value (RDV) evolves over time with a slope that depends on what the subject is looking at. In addition to the average drift, there is also Gaussian noise. When the RDV reaches one of the two barriers the subject makes the corresponding choice. The shaded regions indicate what the subject is currently looking at, blue for the product and yellow for the price. (B) Timeline. (Top) Subjects first reveal how much they are willing to pay for each of the 50 products, using a BDM auction. Then subjects make 300 purchasing choices (the 50 products at six different prices). At the end of the experiment one trial from the combined tasks is randomly chosen and the subject is paid and/or is shipped the chosen product. (Bottom) Within a choice trial, subjects must first fixate at the center of the screen for 2 s. They are then presented with an item and a price and given unlimited self-paced time to decide whether to buy the item at that price.