We describe evidence consistent with the proposal that the visual system contains a parallel array of size-tuned mechanisms sensitive to orientation texture-defined (OTD) form, and propose that the relative activity of these mechanisms determines spatial frequency discrimination threshold for OTD gratings. Using a pattern of short lines we measured spatial frequency discrimination thresholds fo...

Hernán A. Makse, José S. Andrade, Jr., Michael Batty, Shlomo Havlin, and H. Eugene Stanley Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 Departamento de Fı́sica, Universidade Federal do Ceará, 60451-970 Fortaleza, Ceará, Brazil Centre for Advanced Spatial Analysis, University College London, 1-19 Torrington Place, London WC1E 6BT, United Kin...

This paper examines if the joint behavior of inflation and relative price variability (RPV) is consistent with threshold nonlinearity. It applies the test procedure proposed by Tsay (1998) to monthly inflation and RPV in the U.S. for a period from January 1947 to October 2000, and finds strong evidence in favor of threshold nonlinearity that signifies asymmetries of the relationship between inf...

22 23 Whether a link exists between the two orienting processes of saccade preparation and 24 visuospatial attention has typically been studied by using either sensory cues or pre25 determined rules that instruct subjects where to allocate these limited resources. In the 26 real world, explicit instructions are not always available and presumably expectations 27 shaped by previous experience pl...

Predicting species distributions at scales of regions to continents is often necessary, as largescale phenomena influence the distributions of spatially structured populations. Land use and land cover are important large-scale drivers of species distributions, and landscapes are known to create species occurrence thresholds, where small changes in a landscape characteristic results in abrupt ch...

We study a model of a multi-species ecosystem described by Lotka-Volterra-like equations. Interactions among species form a network whose evolution is determined by the dynamics of the model. Numerical simulations show power-law distribution of intervals between extinctions, but only for ecosystems with sufficient variability of species and with networks of connectivity above certain threshold ...

We investigated the possibility that the spatial imprecision of amblyopic eyes can be accounted for by the relative insensitivity to contrast that has been documented for these eyes. Thresholds for the discrimination of spatial misalignment, a measure of spatial uncertainty, were determined for three amblyopes and one normal for targets ranging in contrast from detection threshold to 99%. We fo...