The effect of stimulus presentation time on bias: A diffusion-model based analysis

AbstractThere are two main types of bias in simple decision tasks, response bias and stimulus bias. Response bias is a starting level of evidence in favor of a biased response, whereas stimulus bias is the evaluation of stimuli in favor of a biased response. Previous research typically dissociates between these two types of bias. Some studies suggest that it can be difficult to induce response bias without stimulus bias (Ratcliff & McKoon, 2008; van Ravenzwaaij, Mulder, Tuerlinckx, & Wagenmakers, 2012). We used a two-alternative forced-choice brightness discrimination task in which we manipulated the presentation length of the stimuli. We analyzed the data with a hierarchical diffusion model. The results show an overall response bias, as well as stimulus bias that increases as stimulus presentation time decreases. We argue that the results suggest a need to revise how stimulus bias is conceptualized through the drift rate parameter of the diffusion model.


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