The counterintuitive impact of responses and response times on parameter estimates in the drift diffusion model

Given a drift diffusion model with unknown drift and boundary parameters, we analyse the behaviour of maximum likelihood estimates with respect to changes of responses and response times. It is shown analytically that a single fast response time can dominate the estimation in that no matter how many correct answers a test taker provides, the estimate of the drift (ability) parameter decreases to zero. In addition, it is shown that although higher drift rates imply shorter response times, the reverse implication does not hold for the estimates: shorter response times can decrease the drift rate estimate. In the light of these analytical results, we illustrate the actual impact of the findings in a small simulation for a mental rotation test. The method of analysis outlined is applicable to a broader range of models, and we emphasize the need to further check currently used reaction time models within this framework.     

Health: Introductory paper

The notion of confidence is essential if there is to be any dialogue within the family about questions of health. The international and ecological aspects of health problems must, however, also be incorporated.     

Creating coherence in real‐life decision processes: Reasons,differentiation and consolidation

Svenson, O. & Jakobsson, M. (2009). Creating coherence in real‐life decision processes: Reasons, differentiation and consolidation. Scandinavian Journal of Psychology, 51, 93–102. Differentiation and Consolidation Theory describes human decision making as a process in which attractiveness values are restructured in order to reach a decision and support the decision made. Here, the theory was developed to include reasons pro and con alternatives and tested on students making decisions between two university psychotherapy training programs (cognitive‐behavioral and psychodynamic therapy). Before and also after the decision, the attractiveness of the chosen alternative was upgraded and the non‐chosen alternative downgraded. Different measures of evaluations of an alternative, such as “best” or “worse” converged over time until shortly after the decision. The number of reasons pro and con alternatives give a more complete picture than attractiveness and increased from the first to the last session. The reasons supporting the chosen alternative increased in strength, but reasons against the non‐chosen alternative decreased. In informal comments participants reported that the study also served as a decision aid.