Behavioral Social Neuroscience Seminar

I will discuss the diffusion model for perceptual and cognitive two-choice decisions. The model is reviewed in Ratcliff and McKoon (2008): http://star.psy.ohio-state.edu/html/coglab/Research/neuralcomp08.pdf I will explain how the model works, how it accounts for difficulty, speed-accuracy tradeoffs, error response times (RTs), and RT distributions. One of the major contributions of the model is that it solves a long-standing problem for decision-making models, specifically, the relationship between correct and error RTs. It solves this problem with the assumption that the parameters of the model vary in their values from trial to trial. I will also describe recent studies in which we have used the model to examine differences in processing between college-age students and older adults. We have found that in several paradigms, namely, numerosity discrimination, recognition memory, and lexical decision, the rate of accumulation of evidence in the decision process is not significantly different for the two groups. Longer RTs for the older adults come from more conservative decision criteria and from a small increase in the nondecision components of processing. In contrast, in associative recognition, the older adults' longer RTs come from a reduced rate of accumulation of evidence, as well as more conservative decision criteria and a small increase in the nondecision components of processing. In addition to these differences between groups, the model extracts meaningful differences among individuals such that their parameters correlate across tasks. The model also allows calculations of the optimality with which individuals make decisions in two-choice tasks, but I argue that decision criterion settings are not dictated by optimality in the sense it has been used.