The human brain faces a variety of computational dilemmas, including the flexibility/stability, the speed/accuracy and the labor/leisure tradeoff. I will argue that striatal dopamine is particularly well suited to dynamically regulate these computational tradeoffs depending on constantly changing task demands. This working hypothesis is grounded in evidence from recent studies on learning, motivation and cognitive control in human volunteers, using chemical PET, psychopharmacology, and/or fMRI. These studies also begin to elucidate the mechanisms underlying the huge variability in catecholaminergic drug effects across different individuals and across different task contexts. For example, I will demonstrate how effects of the most commonly used psychostimulant methylphenidate on learning, Pavlovian and effortful instrumental control depend on fluctuations in current environmental volatility, on individual differences in working memory capacity and on opportunity cost respectively.

It seems we see the world in full detail. However, the eye is not a camera nor is the brain a computer. Incredible metabolic constraints render us unable to encode more than a fraction of information available in each glance. Instead, our illusion of stable and complete perception is accomplished by parsimonious representation relying on natural order inherent in the surrounding environment. I will begin by discussing previous behavioral work from our lab demonstrating one such strategy by which the visual system represents average properties of Gestalt-grouped sets of individual objects, warping individual object representations toward the Gestalt-defined mean. I will then discuss on-going work using a behavioral index of averaging Gestalt-grouped information established in our previous work in conjunction with an ERP-index of VSTM capacity (the CDA) to measure whether the Gestalt-grouping and perceptual averaging strategy acts to boost memory capacity above the classic “four-item” limit. Finally, I will outline our pre-registered study to determine whether this perceptual strategy is indeed engaged in a “smart” manner under normal circumstances, or compromises fidelity for capacity by perceptually-averaging in trials with only four items that could otherwise be individually represented.