Investigating Decision-Making with Insufficient Evidence Using Behavioral Modeling

Obliging to make decisions with only limited and sometimes insufficient evidence is one of the challenges that we face. Previous studies have examined the effect of evidence on performance, confidence, and response time. The question of what leads to a decision with insufficient evidence is still shrouded in ambiguity. This research tries to find an answer by experimenting with random dot motion tasks and using behavioral modeling.

A random dot motion psychophysics experiment was designed and 10 participants were asked to indicate the direction of dots and the degree of their confidence after observing the movement of the dots. In this experiment, the duration of stimulus display was variable and, in each trial, randomly had one of the six specified durations (80 to 720 milliseconds). As the stimulus display time varied, participants were exposed to sufficient and insufficient evidence to make a decision. The results of the participants' behavioral data were analyzed by psychometric functions and the participants' behavior was modeled using the drift-diffusion model.

Our behavioral data indicate that the duration of stimulus display has a significant impact on increasing accuracy and confidence as well as on reducing response time. Behavioral modeling results also showed that the decision components (i.e., threshold separation, drift rate, and none-decision time) are affected by changes in stimulus duration, and threshold separation is significantly affected. The threshold separation increases significantly as the stimulus shows increases.

Our investigation supports the hypothesis that the brain changes the decision threshold and adapts to the situation when making decisions based on insufficient evidence.