1,799 research outputs found
Success-First Decision Theories
The standard formulation of Newcomb's problem compares evidential and causal conceptions of
expected utility, with those maximizing evidential expected utility tending to end up far richer. Thus, in a
world in which agents face Newcomb problems, the evidential decision theorist might ask the causal
decision theorist: "if you're so smart, why ainâcha rich?â Ultimately, however, the expected riches of
evidential decision theorists in Newcomb problems do not vindicate their theory, because their success
does not generalize. Consider a theory that allows the agents who employ it to end up rich in worlds
containing Newcomb problems and continues to outperform in other cases. This type of theory, which I
call a âsuccess-firstâ decision theory, is motivated by the desire to draw a tighter connection between
rationality and success, rather than to support any particular account of expected utility. The primary aim
of this paper is to provide a comprehensive justification of success-first decision theories as accounts of
rational decision. I locate this justification in an experimental approach to decision theory supported by the aims of methodological naturalism
Perceptual learning in parafoveal vision
AbstractThe present study tests the effects of practice on parafoveal vernier and resolution acuity. By measuring task specificity, transfer of training to other retinal locations in the trained eye and transfer of training to the untrained eye, we directly address whether improvement on these tasks is the result of changes in the underlying physiological processes or simply the development of new cognitive strategies. We found that: (1) significant learning can occur for both vernier and resolution acuity in many (but not all) individuals; (2) there were significant individual differences in the degree and time-course of learning: (3) learning transfers to the untrained task; and (4) learning transfers to the other eye particularly when the visual pathway leads to the trained hemisphere. These results suggest that both physiological and cognitive processes contribute to the improvement seen after repetitive practice on these visual tasks
Dynamic random noise shrinks the twinkling aftereffect induced by artificial scotomas
AbstractPhysiological alterations in cortical neurons are induced during adaptation to an artificial scotoma, a small homogeneous patch within a dynamic random noise or patterned background. When the dynamic noise is replaced by an equiluminant gray background, a twinkling aftereffect can be seen in the location of the artificial scotoma. Following binocular adaptation, we discovered that the perceived size of the twinkling aftereffect was dramatically smaller than the inducing artificial scotoma. Dichoptic adaptation induced shrinkage in the twinkling aftereffect that was similar to that found after binocular adaptation, suggesting that the twinkling aftereffect and its shrinkage both have cortical origins. We speculate that this perceptual shrinkage may reflect the interaction between two cortical mechanisms: a twinkling aftereffect mechanism that spreads throughout the artificial scotoma, and a filling-in mechanism that has a greater influence at the edges of the artificial scotoma and spreads inwards
Geometric Phase and Helicity Inversion of Photons Propagating inside a Noncoplanarly Curved Optical Fiber
The Letter presents an exact expression for the non-adiabatic non-cyclic
geometric phase of photons propagating inside a noncoplanarly curved optical
fiber by using the Lewis-Riesenfeld invariant theory. It is shown that the
helicity inversion of photons arises in the curved fiber. Since we have exactly
solved the time-dependent Schr\"{o}dinger equation that governs the propagation
of photons in a curved fiber and, moreover, the chronological product is not
involved in this exact solution, our formulation therefore has several
advantages over other treatments based on the classical Maxwell's theory and
the Berry's adiabatic quantum theory. The potential application of helicity
inversion of photons to information science is briefly suggested.Comment: 8 pages, Latex. accepted by Phys. Lett.
Patterns of Information Behavior and Prostate Cancer Knowledge Among African-American Men
The purposes of this study are to explore cancer information acquisition patterns among African-American men and to evaluate relationships between information acquisition patterns and prostate cancer prevention and control knowledge. A random sample of 268 men participated in a statewide interviewer-administered, telephone survey. Men classified as non-seekers, non-medical source seekers, and medical source seekers of prostate cancer information differed on household income, level of education, and beliefs about personal risk for developing prostate cancer. Results from multiple regression analysis indicated that age, education, and information-seeking status were associated with overall levels of prostate cancer knowledge. Results from logistic regression analyses indicated that men who included physicians as one of many information resources (medical source seekers) had superior knowledge over non-seekers and non-medical source seekers on 33% of individual knowledge details. The findings emphasize the need to connect lower-income and lower-educated African-American men to physicians as a source of prostate cancer control information
Vacuum Solutions of Einstein's Equations in Parabolic Coordinates
We present a simple method to obtain vacuum solutions of Einstein's equations
in parabolic coordinates starting from ones with cylindrical symmetries.
Furthermore, a generalization of the method to a more general situation is
given together with a discussion of the possible relations between our method
and the Belinsky-Zakharov soliton-generating solutions.Comment: 15 pages, version published in Class. Quantum Gra
Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California river
Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the SacramentoâSan Joaquin River system form the backbone of Californiaâs salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery- versus wild-spawned salmon is vital for assessing the status and resiliency of wild salmon populations. Here, we reconstructed the proportion of hatchery fish on natural spawning grounds in the Feather River, a major tributary to the Sacramento River, using strontium isotope (87Sr/86Sr) ratios of otoliths collected during carcass surveys from 2002 to 2010. Our results show that prior to the 2007â2008 salmon stock collapse, 55%â67% of in-river spawners were of hatchery origin; however, hatchery contributions increased drastically (89%) in 2010 following the collapse. Data from a recent hatchery marking program corroborate our results, showing that hatchery fish continued to dominate (âŒ90%) in 2011â2012. Though the rebound in abundance of salmon in the Feather River suggests recovery of the stock postcollapse, our otolith chemistry data document a persistent decline of wild spawners, likely leading to the erosion of locally adapted Feather River salmon populations
Gyroscope precession in cylindrically symmetric spacetimes
We present calculations of gyroscope precession in spacetimes described by
Levi-Civita and Lewis metrics, under different circumstances. By doing so we
are able to establish a link between the parameters of the metrics and
observable quantities, providing thereby a physical interpretation for those
parameters, without specifying the source of the field.Comment: 13 pages, Latex. To appear in Class.Q.Gra
Nonlinear Realization of Chiral Symmetry on the Lattice
We formulate lattice theories in which chiral symmetry is realized
nonlinearly on the fermion fields. In this framework the fermion mass term does
not break chiral symmetry. This property allows us to use the Wilson term to
remove the doubler fermions while maintaining exact chiral symmetry on the
lattice. Our lattice formulation enables us to address non-perturbative
questions in effective field theories of baryons interacting with pions and in
models involving constituent quarks interacting with pions and gluons. We show
that a system containing a non-zero density of static baryons interacting with
pions can be studied on the lattice without encountering complex action
problems. In our formulation one can also decide non-perturbatively if the
chiral quark model of Georgi and Manohar provides an appropriate low-energy
description of QCD. If so, one could understand why the non-relativistic quark
model works.Comment: 34 pages, 2 figures, revised version to be published in J. High
Energy Phys. (changes in the 1st paragraph, additional descriptions on the
nature of the coordinate singularities in Sec.2, references added
Thinking like a man? The cultures of science
Culture includes science and science includes culture, but conflicts between the two traditions persist, often seen as clashes between interpretation and knowledge. One way of highlighting this false polarity has been to explore the gendered symbolism of science. Feminism has contributed to science studies and the critical interrogation of knowledge, aware that practical knowledge and scientific understanding have never been synonymous. Persisting notions of an underlying unity to scientific endeavour have often impeded rather than fostered the useful application of knowledge. This has been particularly evident in the recent rise of molecular biology, with its delusory dream of the total conquest of disease. It is equally prominent in evolutionary psychology, with its renewed attempts to depict the fundamental basis of sex differences. Wars over science have continued to intensify over the last decade, even as our knowledge of the political, economic and ideological significance of science funding and research has become ever more apparent
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