Asymmetries in blue-yellow color perception and in the color of 'the dress'.

The perception of color poses daunting challenges, because the light spectrum reaching the eye depends on both the reflectance of objects and the spectrum of the illuminating light source. Solving this problem requires sophisticated inferences about the properties of lighting and surfaces, and many striking examples of 'color constancy' illustrate how our vision compensates for variations in illumination to estimate the color of objects (for example [1-3]). We discovered a novel property of color perception and constancy, involving how we experience shades of blue versus yellow.

Neural bases of individual variation in decision time.

People make decisions by evaluating existing evidence against a threshold or level of confidence. Individuals vary widely in response times even when they perform a simple task in the laboratory. We examine the neural bases of this individual variation by combining computational modeling and brain imaging of 64 healthy adults performing a stop signal task.

The influence of risky and conservative mental sets on cerebral activations of cognitive control.

Mental set is known to influence cognitive functioning. Risk-seeking and risk-aversive mental sets alter cerebral responses to conflicting events. Here, building on our previous imaging work of the stop signal task, we introduced a "reward uncertainty" condition to elicit changes in participants' mental sets and examined how individual differences altered the neural responses to salient events.

The effects of age on cerebral activations: internally versus externally driven processes.

Numerous studies using functional magnetic resonance imaging (fMRI) have described increased or decreased regional brain activations in older as compared to younger adults. This seeming inconsistency may reflect differences in the psychological constructs examined across studies. We hypothesized that behavioral tasks/contrasts engaging internally and externally driven processes are each associated with age-related decreases and increases, respectively, in cerebral activations.