Second harmonic generation (SHG) can be used as a technique for controlling the spatial mode structure of optical beams. We demonstrate experimentally the generation of higher-order spatial modes, and the possibility to use nonlinear phase matching as a predictable and robust technique for the conversion of transverse electric modes of the second harmonic output. The details of this effect are ...

We compared thresholds for discriminating spatial frequency for children aged 5, 7, and 9 years, and adults at two baseline spatial frequencies (1 and 3 cpd). In Experiment 1, the minimum change from baseline necessary to detect a change in spatial frequency from either baseline decreased with age from 34% in 5-year-olds to 11% in 7-year-olds, 8% in 9-year-olds, and 6% in adults. The data were ...

The main purpose of these experiments was to examine in detail how successfully the uncertainty reduction explanation accounts for the effects of spatial cues in a temporal forced-choice contrast discrimination task in which any one of four well-separated Gabor patches is incremented. In preliminary experiments, it was shown that in the absence of uncorrelated contrast jitter, observers could u...

This paper explores the potential for mapping with Geographic Information System (GIS) technology and Exploratory Spatial Data Analysis techniques using several different software packages to contribute to an understanding of housing discrimination in the City of Philadelphia. The primary research question is whether spatial statistical analysis offers insight beyond that provided by visual ana...

We investigated whether the statistical predictability of a target's location would influence how quickly and accurately it was classified. Recent results have suggested that spatial probability can be a cue for the allocation of attention in visual search. One explanation for probability cuing is spatial repetition priming. In our two experiments we used probability distributions that were con...

A familiar result in the literature on mergers is that the principal beneficiaries from such activity are the firms which are excluded from participation. The possible existence of this ‘merger paradox’ contrasts strongly with the frequently expressed view that merger is anti-competitive. This paper examines the question within the context of a model of spatial competition in which firms choose...

PURPOSE The visual deficit in amblyopia involves both elevated contrast thresholds and distorted suprathreshold percepts at high spatial frequencies. It is currently unclear whether these two anomalies are part of the same neural disturbance or whether they reflect different neural dysfunction. METHODS The quality of the spatial percepts in amblyopia was assessed at detection threshold. The a...

We compared the number of spatial frequency and orientation mechanisms underlying first- versus second-order processing by measuring discrimination at detection threshold for first- and second-order Gabors to determine the smallest difference in spatial frequency and orientation that permits accurate discrimination at threshold. For second-order gratings, the number of channels is the same as f...

The human visual system is spatially inhomogenous, and this property should be included in models of visual processing. We used weighted Hermite polynomials (WHPs) to encode and to characterize such inhomogenous processing. Simulations using an order-transfer-function (OTF) defined for each WHP order, at three spatial scales, provide elegant predictions of variations in two-point resolution and...

Groups of five to seven macaques were trained on repeated reversals of a visual (or spatial) discrimination habitafter no pretraining, extended discrimination training, or repeated reversal training on spatial (or visual) cues. Neither sortof pretraining had a significant effect on reversal learning on the second cue. These results indicate that monkeys' capacity to develop generalized "win-sta...