A fast numerical algorithm for the estimation of diffusion model parameters

In this paper, we describe a new algorithmic approach for parameter estimation in Ratcliff's [(1978). A theory of memory retrieval. Psychological Review, 85 (2), 59-108] diffusion model. This problem, especially if inter-trial variabilities of parameters are included in the model, is computationally very expensive; the parameter estimation procedure often takes a long time even with today's high-speed computers. The algorithm described here makes the calculation of the cumulative distribution functions for predicted process durations computationally much less expensive. This improvement is achieved by solving the Kolmogorov backward equation numerically instead of employing the previously used closed form solution. Additionally, the algorithm can determine the optimum fit for one of the model parameters (the starting point z) directly, thereby reducing the dimension of the parameter search space by one. The resulting method is shown to be notably faster than the standard (closed-form solution) method for parameter estimation.     

Accurate forced-choice recognition without awareness of memory retrieval

Recognition confidence and the explicit awareness of memory retrieval commonly accompany accurate responding in recognition tests. Memory performance in recognition tests is widely assumed to measure explicit memory, but the generality of this assumption is questionable. Indeed, whether recognition in nonhumans is always supported by explicit memory is highly controversial. Here we identified circumstances wherein highly accurate recognition was unaccompanied by hallmark features of explicit memory. When memory for kaleidoscopes was tested using a two-alternative forced-choice recognition test with similar foils, recognition was enhanced by an attentional manipulation at encoding known to degrade explicit memory. Moreover, explicit recognition was most accurate when the awareness of retrieval was absent. These dissociations between accuracy and phenomenological features of explicit memory are consistent with the notion that correct responding resulted from experience-dependent enhancements of perceptual fluency with specific stimuli--the putative mechanism for perceptual priming effects in implicit memory tests. This mechanism may contribute to recognition performance in a variety of frequently-employed testing circumstances. Our results thus argue for a novel view of recognition, in that analyses of its neurocognitive foundations must take into account the potential for both (1) recognition mechanisms allied with implicit memory and (2) recognition mechanisms allied with explicit memory.     

The validity and reliability of the Violence Risk Scale-Sexual Offender version: assessing sex offender risk and evaluating therapeutic change

The Violence Risk Scale-Sexual Offender version (VRS-SO) is a rating scale designed to assess risk and predict sexual recidivism, to measure and link treatment changes to sexual recidivism, and to inform the delivery of sexual offender treatment. The VRS-SO comprises 7 static and 17 dynamic items empirically or conceptually linked to sexual recidivism. Dynamic items with higher ratings identify treatment targets linked to sexual offending. A modified stages of change model assesses the offender's treatment readiness and change. File-based VRS-SO ratings were completed on 321 sex offenders followed up an average of 10 years post-release. VRS-SO scores predicted sexual and nonsexual violent recidivism post-release and demonstrated acceptable interrater reliability and concurrent validity. A factor analysis of the dynamic items generated 3 factors labeled Sexual Deviance, Criminality, and Treatment Responsivity, all of which predicted sexual recidivism and were differentially associated with different sex offender types. The dynamic items together made incremental contributions to sexual recidivism prediction after static risk was controlled for. Positive changes in the dynamic items, measured at pre- and posttreatment, were significantly related to reductions in sexual recidivism after risk and follow-up time were controlled for, suggesting that dynamic items are indeed dynamic or changeable in nature.     

The Effect of Disruptions During Counseling on Recall of Genetic Risk Information: The Case of Cystic Fibrosis

Genetic counseling is a communication process with two main functions: information provision and supportive counseling. The information transmission function may be compromised by disruptions that occur during counseling. At least two mediators are possible: (a) disruptions may interfere with memory by creating distractions and divided attention during encoding or (b) disruptions may degrade the flow of interaction which requires that participants engage in conversation repair rather than the task at hand. This study examined both alternatives in a group of parents (N=20 families, 40 individual parents) whose infant had received a newborn screening for cystic fibrosis (CF). Upon arrival at the hospital, each parent completed a questionnaire designed to assess his or her knowledge of CF. Their interaction with the genetic counselor was videotaped and coded for the presence of disruptions. Six weeks after the counseling, parents again completed the knowledge measure. The data showed a direct negative effect for disruptions during counseling on memory for CF-related risk information six weeks later. Disruptions also produced the anticipated effect on conversation, but counter to expectations, interruptions of conversation flow was positively associated with knowledge at time 2.     

How to make your own response boxes: A step-by-step guide for the construction of reliable and inexpensive parallel-port response pads from computer mice

Psychological research is based in large parts on response latencies, which are often registered by keypresses on a standard computer keyboard. Recording response latencies with a standard keyboard is problematic because keypresses are buffered within the keyboard hardware before they are signaled to the computer, adding error variance to the recorded latencies. This can be circumvented by using external response pads connected to the computer's parallel port. In this article, we describe how to build inexpensive, reliable, and easy-to-use response pads with six keys from two standard computer mice that can be connected to the PC's parallel port. We also address the problem of recording data from the parallel port with different software packages under Microsoft's Windows XP.     

Fast-dm: A free program for efficient diffusion model analysis

In the present article, a flexible and fast computer program, called fast-dm, for diffusion model data analysis is introduced. Fast-dm is free software that can be downloaded from the authors' websites. The program allows estimating all parameters of Ratcliff's (1978) diffusion model from the empirical response time distributions of any binary classification task. Fast-dm is easy to use: it reads input data from simple text files, while program settings are specified by commands in a control file. With fast-dm, complex models can be fitted, where some parameters may vary between experimental conditions, while other parameters are constrained to be equal across conditions. Detailed directions for use of fast-dm are presented, as well as results from three short simulation studies exemplifying the utility of fast-dm.     

The aftermath of 9/11: effect of intensity and recency of trauma on outcome

Does trauma exposure have a long-term impact on the brain and behavior of healthy individuals? The authors used functional magnetic resonance imaging to assess the impact of proximity to the disaster of September 11, 2001, on amygdala function in 22 healthy adults. More than three years after the terrorist attacks, bilateral amygdala activity in response to viewing fearful faces compared to calm ones was higher in people who were within 1.5 miles of the World Trade Center on 9/11, relative to those who were living more than 200 miles away (all were living in the New York metropolitan area at time of scan). This activity mediated the relationship between group status and current symptoms of posttraumatic stress disorder. In turn, the effect of group status on both amygdala activation (fearful vs. calm faces) and current symptoms was statistically explained by time since worst trauma in lifetime and intensity of worst trauma, as indicated by reported symptoms at time of the trauma. These data are consistent with a model of heightened amygdala reactivity following high-intensity trauma exposure, with relatively slow recovery.     

Defining ‘Modern’ Malay womanhood and the coexistent messages of the veil

The gender constructions and performances of Malay women are often perceived by outside researchers as ‘shrouded under a veil’ of increasing Islamic conservatism. Urban Malay women, however, argue that women actively engage in the construction and performance of gender identities. Based on research conducted in Kuala Lumpur, Malaysia, during 2001 and 2003, this article argues that women advantageously alter, transform and utilise the constructs placed upon them by Islam, by ethnic identification and by conceptions of ‘modernity’. Often one image of ‘womanhood’ is presented and in public - an image that is socially accepted, honoured and respected - while less publicly alternative forms of ‘womanhood’ articulate individual goals and aims. Using an agent-oriented perspective, this article further includes an analysis of women's individual renegotiations of larger cultural constructs and the ways in which the tudong, or headscarf, has become a symbol by which individual women express their understanding of social position and personal freedoms in an industrialised Islamic context.