Brown University

About: Brown University is a education organization based out in Providence, Rhode Island, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 35778 authors who have published 90896 publications receiving 4471489 citations. The organization is also known as: brown.edu & Brown.

Acting Optimally in Partially Observable Stochastic Domains

Abstract: In this paper, we describe the partially observable Markov decision process (POMDP) approach to finding optimal or near-optimal control strategies for partially observable stochastic environments, given a complete model of the environment. The POMDP approach was originally developed in the operations research community and provides a formal basis for planning problems that have been of interest to the AI community. We found the existing algorithms for computing optimal control strategies to be highly computationally inefficient and have developed a new algorithm that is empirically more efficient. We sketch this algorithm and present preliminary results on several small problems that illustrate important properties of the POMDP approach.

Differential responses to psychotherapy versus pharmacotherapy in patients with chronic forms of major depression and childhood trauma

Abstract: Major depressive disorder is associated with considerable morbidity, disability, and risk for suicide. Treatments for depression most commonly include antidepressants, psychotherapy, or the combination. Little is known about predictors of treatment response for depression. In this study, 681 patients with chronic forms of major depression were treated with an antidepressant (nefazodone), Cognitive Behavioral Analysis System of Psychotherapy (CBASP), or the combination. Overall, the effects of the antidepressant alone and psychotherapy alone were equal and significantly less effective than combination treatment. Among those with a history of early childhood trauma (loss of parents at an early age, physical or sexual abuse, or neglect), psychotherapy alone was superior to antidepressant monotherapy. Moreover, the combination of psychotherapy and pharmacotherapy was only marginally superior to psychotherapy alone among the childhood abuse cohort. Our results suggest that psychotherapy may be an essential element in the treatment of patients with chronic forms of major depression and a history of childhood trauma.

Appropriate growth policy: a unifying framework

Abstract: In this lecture, we use Schumpeterian growth theory, where growth comes from qualityimproving innovations, to elaborate a theory of growth policy and to explain the growth gap between Europe and the US. Our theoretical apparatus systematizes the case-by-case approach to growth policy design. The emphasis is on three policy areas that are potentially relevant for growth in Europe, namely: competition and entry, education, and macropolicy. We argue that higher entry and exit (higher firm turnover) and increased emphasis on higher education are more growth-enhancing in countries that are closer to the technological frontier. We also argue that countercyclical budgetary policies are more growth-enhancing in countries with lower financial development. The analysis thus points to important interaction effects between policies and state variables, such as distance to frontier or financial development, in growth regressions. Finally, we argue that the other endogenous growth models, namely the AK and product variety models, fail to account for the evidence on the relationship between competition, education, volatility, and growth, and consequently cannot deliver relevant policy prescriptions in the three areas we consider. (JEL: O20, O30, O40)

Psychophysical support for a two-dimensional view interpolation theory of object recognition

Abstract: Does the human brain represent objects for recognition by storing a series of two-dimensional snapshots, or are the object models, in some sense, three-dimensional analogs of the objects they represent? One way to address this question is to explore the ability of the human visual system to generalize recognition from familiar to unfamiliar views of three-dimensional objects. Three recently proposed theories of object recognition--viewpoint normalization or alignment of three-dimensional models [Ullman, S. (1989) Cognition 32, 193-254], linear combination of two-dimensional views [Ullman, S. & Basri, R. (1990) Recognition by Linear Combinations of Models (Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge), A. I. Memo No. 1152], and view approximation [Poggio, T. & Edelman, S. (1990) Nature (London) 343, 263-266]--predict different patterns of generalization to unfamiliar views. We have exploited the conflicting predictions to test the three theories directly in a psychophysical experiment involving computer-generated three-dimensional objects. Our results suggest that the human visual system is better described as recognizing these objects by two-dimensional view interpolation than by alignment or other methods that rely on object-centered three-dimensional models.