“Subject alternately fixates on each of two proffered snacks, before choosing one. [The image shows the] average path of the decision variable according to the Krajbich model for three parameter settings. The decision variable ramps toward the left or right choice boundaries, with the slope determined by the true relative subjective value of the items (here, left is preferred), but biased to slope toward the item currently being fixated. The biases depicted are: high (green), medium (red, as actually inferred from the data) or none (blue). Clocks depict the excess time spent looking at the left versus the right option at each step.”

TL;DR The leaning of the decision-maker is influenced by which choice they’re currently looking at, getting stronger with time, until a threshold is reached where the decision is made. A more eye-catching item is therefore more likely to be chosen because it gets more sight-time.

Link to article. Although technically OP’s image is from a paper that yoinked the left half of the figure to waffle on about some economics bs. But this is the original source.