On the mean and variance of response times under the diffusion model with an application to parameter estimation

We give closed form expressions for the mean and variance of RTs for Ratcliff’s diffusion model [Ratcliff, R. (1978). A theory of memory retrieval. Psychological Review, 85, 59-108] under the simplifying assumption that there is no variability across trials in the parameters. These expressions are more general than those currently available. As an application, we demonstrate their use in a method-of-moments estimation procedure that addresses some of the weaknesses of the EZ method [Wagenmakers, E.-J., van der Maas, H. L. J., & Grasman, R. P. P. P. (2007). An EZ-diffusion model for response time and accuracy. Psychonomic Bulletin & Review, 14, 3-22], and illustrate this with lexical decision data. We discuss further possible applications.     

An EZ-diffusion model for response time and accuracy

The EZ-diffusion model for two-choice response time tasks takes mean response time, the variance of response time, and response accuracy as inputs. The model transforms these data via three simple equations to produce unique values for the quality of information, response conservativeness, and nondecision time. This transformation of observed data in terms of unobserved variables addresses the speed—accuracy trade-off and allows an unambiguous quantification of performance differences in two-choice response time tasks. The EZ-diffusion model can be applied to data-sparse situations to facilitate individual subject analysis. We studied the performance of the EZ-diffusion model in terms of parameter recovery and robustness against misspecification by using Monte Carlo simulations. The EZ model was also applied to a real-world data set.     

Value-based decision-making battery: A Bayesian adaptive approach to assess impulsive and risky behavior

Using simple mathematical models of choice behavior, we present a Bayesian adaptive algorithm to assess measures of impulsive and risky decision making. Practically, these measures are characterized by discounting rates and are used to classify individuals or population groups, to distinguish unhealthy behavior, and to predict developmental courses. However, a constant demand for improved tools to assess these constructs remains unanswered. The algorithm is based on trial-by-trial observations. At each step, a choice is made between immediate (certain) and delayed (risky) options. Then the current parameter estimates are updated by the likelihood of observing the choice, and the next offers are provided from the indifference point, so that they will acquire the most informative data based on the current parameter estimates. The procedure continues for a certain number of trials in order to reach a stable estimation. The algorithm is discussed in detail for the delay discounting case, and results from decision making under risk for gains, losses, and mixed prospects are also provided. Simulated experiments using prescribed parameter values were performed to justify the algorithm in terms of the reproducibility of its parameters for individual assessments, and to test the reliability of the estimation procedure in a group-level analysis. The algorithm was implemented as an experimental battery to measure temporal and probability discounting rates together with loss aversion, and was tested on a healthy participant sample.     

Control of rapid aimed hand movements: the one-target advantage

A series of 8 experiments examined the phenomenon that a rapid aimed hand movement is executed faster when it is performed as a single, isolated movement than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movement hypothesis, the target uncertainty hypothesis, and the movement integration hypothesis. Data are reported that corroborate the 3rd hypothesis, but not the first 2 hypotheses. According to the movement integration hypothesis, the first movement in a series is slowed because control of the second movement may overlap with execution of the first. It is shown that manipulations of target size and movement direction mediate this process and determine the presence and absence of the 1-target advantage. Possible neurophysiological mechanisms and implications for motor control theory are discussed.     

Effects of Gender on Costly Punishment

Women are often believed to be more cooperative and less egoistic than men. In the present study, we examined whether people punish women for failing to live up to these benevolent gender stereotypes. Participants played a prisoner's dilemma game with female and male partners who either cooperated or defected. Participants were offered a costly punishment option. They could spend money to decrease the payment of their partners. In Experiment 1, participants spent more money to punish the defection of female in comparison to male partners, but this effect of partner gender on punishment was indirect rather than direct: Participants were more likely to cooperate with female partners than with male partners, which gave them more opportunity for moralistic punishment. In Experiments 2 and 3, we examined the effects of the participants' own gender on cooperation and punishment of female and male partners. Female participants cooperated more with female partners than with male partners while male participants treated female and male partners equally. We conclude that the effect of facial gender on punishment are indirect rather than direct. The results also showed that women, in contrast to men, tended to make decisions that can be considered more social and less rational from an economic point of view, consistent with social‐role theory and evolutionary accounts. Copyright © 2017 John Wiley & Sons, Ltd.     

Semantic priming by irrelevant speech

To-be-ignored, task-irrelevant speech disrupts serial recall performance relative to a quiet control condition. In most studies, the content of the auditory distractors had no effect on their disruptive potential, one’s own name being one of the few exceptions. There are two possible explanations of this pattern: (1) Semantic features of the irrelevant speech are usually not processed, except for highly relevant auditory distractors, or (2) semantic processing of the irrelevant speech always occurs, but usually does not affect serial recall performance. To test these explanations, we presented to-be-ignored auditory distractor words drawn from different categories while participants memorized visual targets for serial recall. Afterwards, participants were invited to what they believed to be an unrelated norming study, in which they were required to spontaneously produce words from the categories from which the auditory distractor words were drawn. Previously ignored words were produced with a higher probability than words from a parallel, nonpresented set, demonstrating that features of to-be-ignored, task-irrelevant speech that do not interfere with immediate serial recall performance are nevertheless processed semantically and may have substantial effects on subsequent behavior.