Aging and individual differences in rapid two-choice decisions

The effects of aging on performance were examined in signal detection, letter discrimination, brightness discrimination, and recognition memory, with each subject tested on all four tasks. Ratcliff’s (1978) diffusion model was fit to the data for each subject for each task, and it provided a good account of accuracy and the distributions of correct and error response times. The model’s analysis of the components of processing showed that aging had three main effects: The nondecision components of processing were slower and the decision criteria were more conservative for 60- to 74-year-old and 75- to 85-year-old subjects than for college students, but the quality of the evidence on which decisions were based was as good for the older subjects as for college students on some of the tasks. Individual differences among subjects in components of processing tended to be preserved across the tasks, as was shown by strong correlations across the tasks in the parameters of the model that represent the components of processing. For example, if the evidence on which a subject’s decisions were based was good in one task, it tended to be good in all four tasks.     

Extinction of conditioned taste aversion depends on functional protein synthesis but not on NMDA receptor activation in the ventromedial prefrontal cortex

We investigated the role of the ventromedial prefrontal cortex (vmPFC) in extinction of conditioned taste aversion (CTA) by microinfusing a protein synthesis inhibitor or N-methyl-d-asparate (NMDA) receptors antagonist into the vmPFC immediately following a non-reinforced extinction session. We found that the protein synthesis blocker anisomycin, but not the NMDA receptors antagonist D,L-2-amino-5-phosphonovaleric acid, impaired CTA extinction in the vmPFC. Anisomycin microinfusion into vmPFC had no effect on CTA acquisition and by itself did not induce CTA. These findings show the necessary role functional protein synthesis is playing in the vmPFC during the learning of CTA extinction.     

Culture, ethnicity, and children's facial expressions: a study of European American, Mainland Chinese, Chinese American, and adopted Chinese girls

This investigation extends previous research documenting differences in Chinese and European American infants' facial expressivity. Chinese girls adopted by European American families, nonadopted Mainland Chinese girls, nonadopted Chinese American girls, and nonadopted European American girls responded to emotionally evocative slides and an odor stimulus. European American girls smiled more than Mainland Chinese and Chinese American girls and scored higher than Mainland Chinese girls for disgust-related expressions and overall expressivity. Adopted Chinese girls produced more disgust-related expressions than Mainland Chinese girls. Self-reported maternal strictness, aggravation, positive expressiveness, and cultural identification correlated with children's facial responses, as did number of siblings and adults in the home. Results suggest that culture and family environment influences facial expressivity, creating differences among children of the same ethnicity.     

Modeling response signal and response time data

The diffusion model (Ratcliff, 1978) and the leaky competing accumulator model (LCA, Usher & McClelland, 2001) were tested against two-choice data collected from the same subjects with the standard response time procedure and the response signal procedure. In the response signal procedure, a stimulus is presented and then, at one of a number of experimenter-determined times, a signal to respond is presented. The models were fit to the data from the two procedures simultaneously under the assumption that responses in the response signal procedure were based on a mixture of decision processes that had already terminated at response boundaries before the signal and decision processes that had not yet terminated. In the latter case, decisions were based on partial information in one variant of each model or on guessing in a second variant. Both variants of the diffusion model fit the data well and both fit better than either variant of the LCA model, although the differences in numerical goodness-of-fit measures were not large enough to allow decisive selection between the models.     

Speeded old-new recognition of multidimensional perceptual stimuli: modeling performance at the individual-participant and individual-item levels

Observers made speeded old-new recognition judgments of color stimuli embedded in a multidimensional similarity space. The paradigm used multiple lists but with the underlying similarity structures repeated across lists, to allow for quantitative modeling of the data at the individual-participant and individual-item levels. Correct-rejection response times (RTs) got systematically faster as the similarity of foils to the old study items decreased. There were also intricate patterns of speed-accuracy trade-offs that varied across individual items and participants. An exemplar-based random-walk model provided a good overall quantitative account of the recognition choice probabilities, mean correct RTs, and mean error RTs associated with the individual items on the basis of their positions in multidimensional similarity space. However, the model failed to predict the very long RTs associated with correct rejections of a prototype foil.