181 research outputs found
You Don't See What I See:Individual Differences in the Perception of Meaning from Visual Stimuli
Everyone has their own unique version of the visual world and there has been growing interest in understanding the way that personality shapes one's perception. Here, we investigated meaningful visual experiences in relation to the personality dimension of schizotypy. In a novel approach to this issue, a non-clinical sample of subjects (total n = 197) were presented with calibrated images of scenes, cartoons and faces of varying visibility embedded in noise; the spatial properties of the images were constructed to mimic the natural statistics of the environment. In two experiments, subjects were required to indicate what they saw in a large number of unique images, both with and without actual meaningful structure. The first experiment employed an open-ended response paradigm and used a variety of different images in noise; the second experiment only presented a series of faces embedded in noise, and required a forced-choice response from the subjects. The results in all conditions indicated that a high positive schizotypy score was associated with an increased tendency to perceive complex meaning in images comprised purely of random visual noise. Individuals high in positive schizotypy seemed to be employing a looser criterion (response bias) to determine what constituted a 'meaningful' image, while also being significantly less sensitive at the task than those low in positive schizotypy. Our results suggest that differences in perceptual performance for individuals high in positive schizotypy are not related to increased suggestibility or susceptibility to instruction, as had previously been suggested. Instead, the observed reductions in sensitivity along with increased response bias toward seeing something that is not there, indirectly implicated subtle neurophysiological differences associated with the personality dimension of schizotypy, that are theoretically pertinent to the continuum of schizophrenia and hallucination-proneness
A Novel Dynamic Morphed Stimuli Set to Assess Sensitivity to Identity and Emotion Attributes in Faces
Face-based tasks are used ubiquitously in the study of human perception and cognition. Video-based (dynamic) face stimuli are increasingly utilized by researchers because they have higher ecological validity than static images. However, there are few ready-to-use dynamic stimulus sets currently available to researchers that include non-emotional and non-face control stimuli. This paper outlines the development of three original dynamic stimulus sets: a set of emotional faces (fear and disgust), a set of non-emotional faces, and a set of car animations. Morphing software was employed to vary the intensity of the expression shown and to vary the similarity between actors. Manipulating these dimensions permits us to create tasks of varying difficulty that can be optimized to detect more subtle differences in face-processing ability. Using these new stimuli, two preliminary experiments were conducted to evaluate different aspects of facial identity recognition, emotion recognition, and non-face object discrimination. Results suggest that these five different tasks successfully avoided floor and ceiling effects in a healthy sample. A second experiment found that dynamic versions of the emotional stimuli were recognized more accurately than static versions, both for labeling, and discrimination paradigms. This indicates that, like previous emotion-only stimuli sets, the use of dynamic stimuli confers an advantage over image-based stimuli. These stimuli therefore provide a useful resource for researchers looking to investigate both emotional and non-emotional face-processing using dynamic stimuli. Moreover, these stimuli vary across crucial dimensions (i.e., face similarity and intensity of emotion) which allows researchers to modify task difficulty as required
The unusual 2006 dwarf nova outburst of GK Perseii
The 2006 outburst of GK Perseii differed significantly at optical and
ultraviolet wavelengths from typical outbursts of this object. We present
multi-wavelength (X-ray, UV and optical) Swift and AAVSO data, giving
unprecedented broad-band coverage of the outburst, allowing us to follow the
evolution of the longer-than-normal 2006 outburst across these wavelengths. In
the optical and UV we see a triple-peaked morphology with maximum brightness
~1.5 magnitudes lower than in previous years. In contrast, the peak hard X-ray
flux is the same as in previous outbursts. We resolve this dichotomy by
demonstrating that the hard X-ray flux only accounts for a small fraction of
the total energy liberated during accretion, and interpret the optical/UV
outburst profile as arising from a series of heating and cooling waves
traversing the disc, caused by its variable density profile.Comment: 9 pages, 7 figures, accepted for publication in MNRA
Texture variations suppress suprathreshold brightness and colour variations
Discriminating material changes from illumination changes is a key function of early vision. Luminance cues are ambiguous in this regard, but can be disambiguated by co-incident changes in colour and texture. Thus, colour and texture are likely to be given greater prominence than luminance for object segmentation, and better segmentation should in turn produce stronger grouping. We sought to measure the relative strengths of combined luminance, colour and texture contrast using a suprathreshhold, psychophysical grouping task. Stimuli comprised diagonal grids of circular patches bordered by a thin black line and contained combinations of luminance decrements with either violet, red, or texture increments. There were two tasks. In the Separate task the different cues were presented separately in a two-interval design, and participants indicated which interval contained the stronger orientation structure. In the Combined task the cues were combined to produce competing orientation structure in a single image. Participants had to indicate which orientation, and therefore which cue was dominant. Thus we established the relative grouping strength of each cue pair presented separately, and compared this to their relative grouping strength when combined. In this way we observed suprathreshold interactions between cues and were able to assess cue dominance at ecologically relevant signal levels. Participants required significantly more luminance and colour compared to texture contrast in the Combined compared to Separate conditions (contrast ratios differed by about 0.1 log units), showing that suprathreshold texture dominates colour and luminance when the different cues are presented in combination
The Willingness to Pay for Mortality Risk Reductions: A Comparison of the United States and Canada
AE Aquarii represents a new subclass of Cataclysmic Variables
We analyze properties of the unique nova-like star AE Aquarii identified with
a close binary system containing a red dwarf and a very fast rotating
magnetized white dwarf. It cannot be assigned to any of the three commonly
adopted sub-classes of Cataclysmic Variables: Polars, Intermediate Polars, and
Accreting non-magnetized White Dwarfs. Our study has shown that the white dwarf
in AE Aqr is in the ejector state and its dipole magnetic moment is . It switched into this state due to intensive mass
exchange between the system components during a previous epoch. A high rate of
disk accretion onto the white dwarf surface resulted in temporary screening of
its magnetic field and spin-up of the white dwarf to its present spin period.
Transition of the white dwarf to the ejector state had occurred at a final
stage of the spin-up epoch as its magnetic field emerged from the accreted
plasma due to diffusion. In the frame of this scenario AE Aqr represents a
missing link in the chain of Polars evolution and the white dwarf resembles a
recycled pulsar.Comment: accepted for publication in Astronomy Reports (July 2012
Euclid preparation. XXIX. Water ice in spacecraft part I: The physics of ice formation and contamination
Molecular contamination is a well-known problem in space flight. Water is the
most common contaminant and alters numerous properties of a cryogenic optical
system. Too much ice means that Euclid's calibration requirements and science
goals cannot be met. Euclid must then be thermally decontaminated, a long and
risky process. We need to understand how iced optics affect the data and when a
decontamination is required. This is essential to build adequate calibration
and survey plans, yet a comprehensive analysis in the context of an
astrophysical space survey has not been done before.
In this paper we look at other spacecraft with well-documented outgassing
records, and we review the formation of thin ice films. A mix of amorphous and
crystalline ices is expected for Euclid. Their surface topography depends on
the competing energetic needs of the substrate-water and the water-water
interfaces, and is hard to predict with current theories. We illustrate that
with scanning-tunnelling and atomic-force microscope images.
Industrial tools exist to estimate contamination, and we must understand
their uncertainties. We find considerable knowledge errors on the diffusion and
sublimation coefficients, limiting the accuracy of these tools. We developed a
water transport model to compute contamination rates in Euclid, and find
general agreement with industry estimates. Tests of the Euclid flight hardware
in space simulators did not pick up contamination signals; our in-flight
calibrations observations will be much more sensitive.
We must understand the link between the amount of ice on the optics and its
effect on Euclid's data. Little research is available about this link, possibly
because other spacecraft can decontaminate easily, quenching the need for a
deeper understanding. In our second paper we quantify the various effects of
iced optics on spectrophotometric data.Comment: 35 pages, 22 figures, A&A in press. Changes to previous version:
language edits, added Z. Bolag as author in the arxiv PDF (was listed in the
ASCII author list and in the journal PDF, but not in the arxiv PDF). This
version is identical to the journal versio
Euclid preparation. TBD. Forecast impact of super-sample covariance on 3x2pt analysis with Euclid
Deviations from Gaussianity in the distribution of the fields probed by
large-scale structure surveys generate additional terms in the data covariance
matrix, increasing the uncertainties in the measurement of the cosmological
parameters. Super-sample covariance (SSC) is among the largest of these
non-Gaussian contributions, with the potential to significantly degrade
constraints on some of the parameters of the cosmological model under study --
especially for weak lensing cosmic shear. We compute and validate the impact of
SSC on the forecast uncertainties on the cosmological parameters for the Euclid
photometric survey, obtained with a Fisher matrix analysis, both considering
the Gaussian covariance alone and adding the SSC term -- computed through the
public code PySSC. The photometric probes are considered in isolation and
combined in the `32pt' analysis. We find the SSC impact to be
non-negligible -- halving the Figure of Merit of the dark energy parameters
(, ) in the 32pt case and substantially increasing the
uncertainties on , and for cosmic shear;
photometric galaxy clustering, on the other hand, is less affected due to the
lower probe response. The relative impact of SSC does not show significant
changes under variations of the redshift binning scheme, while it is smaller
for weak lensing when marginalising over the multiplicative shear bias nuisance
parameters, which also leads to poorer constraints on the cosmological
parameters. Finally, we explore how the use of prior information on the shear
and galaxy bias changes the SSC impact. Improving shear bias priors does not
have a significant impact, while galaxy bias must be calibrated to sub-percent
level to increase the Figure of Merit by the large amount needed to achieve the
value when SSC is not included.Comment: 22 pages, 13 figure
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