150,891 research outputs found
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QuestPlus: A MATLAB Implementation of the QUEST+ adaptive Psychometric Method
QuestPlus is a MATLAB implementation of the QUEST+ adaptive psychometric method. It provides a rapid and flexible method of estimating the parameters of a psychophysical model, and is also capable of advising the user on the most appropriate stimuli to present, and on when to terminate testing. Of particular note is the algorithm’s ability to use prior information, its ability to determine the maximally informative stimulus on each trial, its ability to fit arbitrarily complex models, and its ability to vary multiple stimulus properties simultaneously
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A tutorial on cue combination and Signal Detection Theory: Using changes in sensitivity to evaluate how observers integrate sensory information
Many sensory inputs contain multiple sources of information (‘cues’), such as two sounds of different frequencies, or a voice heard in unison with moving lips. Often, each cue provides a separate estimate of the same physical attribute, such as the size or location of an object. An ideal observer can exploit such redundant sensory information to improve the accuracy of their perceptual judgments. For example, if each cue is modeled as an independent, Gaussian, random variable, then combining Ncues should provide up to a √N improvement in detection/discrimination sensitivity. Alternatively, a less efficient observer may base their decision on only a subset of the available information, and so gain little or no benefit from having access to multiple sources of information. Here we use Signal Detection Theory to formulate and compare various models of cue-combination, many of which are commonly used to explain empirical data. We alert the reader to the key assumptions inherent in each model, and provide formulas for deriving quantitative predictions. Code is also provided for simulating each model, allowing expected levels of measurement error to be quantified. Based on these results, it is shown that predicted sensitivity often differs surprisingly little between qualitatively distinct models of combination. This means that sensitivity alone is not sufficient for understanding decision efficiency, and the implications of this are discussed
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A note on detecting statistical outliers in psychophysical data
This paper considers how to identify statistical outliers in psychophysical datasets, where the underlying sampling distributions are unknown. Eight methods are described, and each is evaluated using Monte Carlo simulations of a typical psychophysical experiment. The best method is shown to be one based on a measure of spread known as S n . This is shown to be more sensitive than popular heuristics based on standard deviations from the mean, and more robust than non-parametric methods based on percentiles or interquartile range. MATLAB code for computing S n is included
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Degraded reality: Using VR/AR to simulate visual impairments
The effects of eye disease cannot be depicted accurately using traditional media. Consequently, public understanding of eye disease is often poor. We present a VR/AR system for simulating common visual impairments, including disability glare, spatial distortions (Metamorphopsia), the selective blurring and filling-in of information across the visual field, and color vision deficits. Unlike most existing simulators, the simulations are informed by patients' self-reported symptoms, can be quantitatively manipulated to provide custom disease profiles, and support gaze-contingent presentation (i.e., when using a VR/AR headset that contains eye-tracking technology, such as the Fove0). Such a simulator could be used as a teaching/empathy aid, or as a tool for evaluating the accessibility of new products and environments
Vibrational transfer functions for complex structures
Evaluation of effects of vibrational multiple frequency forcing functions is discussed. Computer program for developing vibrational transfer functions is described. Possible applications of computer program are enumerated
New polyimide polymer has excellent processing characterisitcs with improved thermo-oxidative and hydrolytic stabilities
Polyimide P10P and its processing technique apply to most high temperature plastic products, devices and castings. Prepolymer, when used as varnish, impregnates fibers directly and is able to be processed into advanced composities. Material may also be used as molding powder and adhesive
Development of Auditory Selective Attention: Why Children Struggle to Hear in Noisy Environments
Children’s hearing deteriorates markedly in the presence of unpredictable noise. To explore why, 187 school-age children (4–11 years) and 15 adults performed a tone-in-noise detection task, in which the masking noise varied randomly between every presentation. Selective attention was evaluated by measuring the degree to which listeners were influenced by (i.e., gave weight to) each spectral region of the stimulus. Psychometric fits were also used to estimate levels of internal noise and bias. Levels of masking were found to decrease with age, becoming adult-like by 9–11 years. This change was explained by improvements in selective attention alone, with older listeners better able to ignore noise similar in frequency to the target. Consistent with this, age-related differences in masking were abolished when the noise was made more distant in frequency to the target. This work offers novel evidence that improvements in selective attention are critical for the normal development of auditory judgments
Application of a multi-site mean-field theory to the disordered Bose-Hubbard model
We present a multi-site formulation of mean-field theory applied to the
disordered Bose-Hubbard model. In this approach the lattice is partitioned into
clusters, each isolated cluster being treated exactly, with inter-cluster
hopping being treated approximately. The theory allows for the possibility of a
different superfluid order parameter at every site in the lattice, such as what
has been used in previously published site-decoupled mean-field theories, but a
multi-site formulation also allows for the inclusion of spatial correlations
allowing us, e.g., to calculate the correlation length (over the length scale
of each cluster). We present our numerical results for a two-dimensional
system. This theory is shown to produce a phase diagram in which the stability
of the Mott insulator phase is larger than that predicted by site-decoupled
single-site mean-field theory. Two different methods are given for the
identification of the Bose glass-to-superfluid transition, one an approximation
based on the behaviour of the condensate fraction, and one of which relies on
obtaining the spatial variation of the order parameter correlation. The
relation of our results to a recent proposal that both transitions are non
self-averaging is discussed.Comment: Accepted for publication in Physical Review
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