1,176 research outputs found
Differential Item Functioning in PISA Due to Mode Effects
One of the most important goals of the Programme for International Student Assessment (PISA) is assessing national changes in educational performance over time. These so-called trend results inform policy makers about the development of ability of 15-year-old students within a specific country. The validity of those trend results prescribes invariant test conditions. In the 2015 PISA survey, several alterations to the test administration were implemented, including a switch from paper-based assessments to computer-based assessments for most countries (OECD 2016a). This alteration of the assessment mode is examined by evaluating if the items used to assess trends are subject to differential item functioning across PISA surveys (2012 vs. 2015). Furthermore, the impact on the trend results due to the change in assessment mode of the Netherlands is assessed. The results show that the decrease reported for mathematics in the Netherlands is smaller when results are based upon a separate national calibration.</p
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Biases in the perceived timing of perisaccadic perceptual and motor events
Subjects typically experience the temporal interval immediately following a saccade as longer than a comparable control interval. One explanation of this effect is that the brain antedates the perceptual onset of a saccade target to around the time of saccade initiation. This could explain the apparent continuity of visual perception across eye movements. Thisantedating account was tested in three experiments in which subjects made saccades of differing extents and then judged either the duration or the temporal order of key events. Postsaccadic stimuli underwent subjective temporal lengthening and had early perceived onsets. A temporally advanced awareness of saccade completion was also found, independently of antedating effects. These results provide convergent evidence supporting antedating and differentiating it from other temporal biases
Exogenous spatial precuing reliably modulates object processing but not object substitution masking
Object substitution masking (OSM) is used in behavioral and imaging studies to investigate processes associated with the formation of a conscious percept. Reportedly, OSM occurs only when visual attention is diffusely spread over a search display or focused away from the target location. Indeed, the presumed role of spatial attention is central to theoretical accounts of OSM and of visual processing more generally (Di Lollo, Enns, & Rensink, Journal of Experimental Psychology: General 129:481–507, 2000). We report a series of five experiments in which valid spatial precuing is shown to enhance the ability of participants to accurately report a target but, in most cases, without affecting OSM. In only one experiment (Experiment 5) was a significant effect of precuing observed on masking. This is in contrast to the reliable effect shown across all five experiments in which precuing improved overall performance. The results are convergent with recent findings from Argyropoulos, Gellatly, and Pilling (Journal of Experimental Psychology: Human Perception and Performance 39:646–661, 2013), which show that OSM is independent of the number of distractor items in a display. Our results demonstrate that OSM can operate independently of focal attention. Previous claims of the strong interrelationship between OSM and spatial attention are likely to have arisen from ceiling or floor artifacts that restricted measurable performance
Visual similarity in masking and priming: The critical role of task relevance
Cognitive scientists use rapid image sequences to study both the emergence of
conscious perception (visual masking) and the unconscious processes involved in
response preparation (masked priming). The present study asked two questions:
(1) Does image similarity influence masking and priming in the same way? (2) Are
similarity effects in both tasks governed by the extent of feature overlap in
the images or only by task-relevant features? Participants in Experiment 1
classified human faces using a single dimension even though the faces varied in
three dimensions (emotion, race, sex). Abstract geometric shapes and colors were
tested in the same way in Experiment 2. Results showed that similarity
reduced the visibility of the target in the masking task
and increased response speed in the priming task, pointing to a
double-dissociation between the two tasks. Results also showed that only
task-relevant (not objective) similarity influenced masking and priming,
implying that both tasks are influenced from the beginning by intentions of the
participant. These findings are interpreted within the framework of a reentrant
theory of visual perception. They imply that intentions can influence object
formation prior to the separation of vision for perception and vision for
action
Study of interplanar binding in graphite by extended Thomas-Fermi theory
A model of a graphite crystal is used which consists of a set of parallel slabs of positive charge immersed in an electron sea. Each slab, about 1 Å wide, contains the charge of the nucleus and five electrons per carbon atom, homogeneously distributed in the volume of the slabs. The electron density in the region between slabs is calculated from Thomas-Fermi-Dirac theory including corrections for inhomogeneity to the kinetic energy and correlation energy. Also, a calculation is reported with the electron density obtained by a minimization of the Thomas-Fermi-Dirac-Kirzhnits functional. The results are in semiquantitative agreement with empirical data
Valence Fluctuations Revealed by Magnetic Field Scan: Comparison with Experiments in YbXCu_4 (X=In, Ag, Cd) and CeYIn_5 (Y=Ir, Rh)
The mechanism of how critical end points of the first-order valence
transitions (FOVT) are controlled by a magnetic field is discussed. We
demonstrate that the critical temperature is suppressed to be a quantum
critical point (QCP) by a magnetic field. This results explain the field
dependence of the isostructural FOVT observed in Ce metal and YbInCu_4.
Magnetic field scan can lead to reenter in a critical valence fluctuation
region. Even in the intermediate-valence materials, the QCP is induced by
applying a magnetic field, at which the magnetic susceptibility also diverges.
The driving force of the field-induced QCP is shown to be a cooperative
phenomenon of the Zeeman effect and the Kondo effect, which creates a distinct
energy scale from the Kondo temperature. The key concept is that the closeness
to the QCP of the FOVT is capital in understanding Ce- and Yb-based heavy
fermions. It explains the peculiar magnetic and transport responses in CeYIn_5
(Y=Ir, Rh) and metamagnetic transition in YbXCu_4 for X=In as well as the sharp
contrast between X=Ag and Cd.Comment: 14 pages, 9 figures, OPEN SELECT in J. Phys. Soc. Jp
Sensorimotor supremacy: Investigating conscious and unconscious vision by masked priming
According to the sensorimotor supremacy hypothesis, conscious perception draws on
motor action. In the present report, we will sketch two lines of potential
development in the field of masking research based on the sensorimotor supremacy
hypothesis. In the first part of the report, evidence is reviewed that masked,
invisible stimuli can affect motor responses, attention shifts, and semantic
processes. After the review of the corresponding evidence – so-called masked
priming effects – an approach based on the sensorimotor supremacy hypothesis is
detailed as to how the question of a unitary mechanism of unconscious vision can
be pursued by masked priming studies. In the second part of the report,
different models and theories of backward masking and masked priming are
reviewed. Types of models based on the sensorimotor hypothesis are discussed
that can take into account ways in which sensorimotor processes (reflected in
masked priming effects) can affect conscious vision under backward masking
conditions
A comparison of large scale atmospheric sulphate aerosol models (COSAM): overview and highlights
Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at GeV
Dihadron azimuthal correlations containing a high transverse momentum (\pt)
trigger particle are sensitive to the properties of the nuclear medium created
at RHIC through the strong interactions occurring between the traversing parton
and the medium, i.e. jet-quenching. Previous measurements revealed a strong
modification to dihadron azimuthal correlations in Au+Au collisions with
respect to \pp\ and \dAu\ collisions. The modification increases with the
collision centrality, suggesting a path-length dependence to the jet-quenching
effect. This paper reports STAR measurements of dihadron azimuthal correlations
in mid-central (20-60\%) Au+Au collisions at \snn=200~GeV as a function of
the trigger particle's azimuthal angle relative to the event plane,
\phis=|\phit-\psiEP|. The azimuthal correlation is studied as a function of
both the trigger and associated particle \pt. The subtractions of the
combinatorial background and anisotropic flow, assuming Zero Yield At Minimum
(\zyam), are described. The away-side correlation is strongly modified, and the
modification varies with \phis, which is expected to be related to the
path-length that the away-side parton traverses. The pseudo-rapidity (\deta)
dependence of the near-side correlation, sensitive to long range \deta
correlations (the ridge), is also investigated. The ridge and jet-like
components of the near-side correlation are studied as a function of \phis.
The ridge appears to drop with increasing \phis while the jet-like component
remains approximately constant. ...Comment: 50 pages, 39 figures, 6 table
Studies of di-jet survival and surface emission bias in Au+Au collisions via angular correlations with respect to back-to-back leading hadrons
We report first results from an analysis based on a new multi-hadron
correlation technique, exploring jet-medium interactions and di-jet surface
emission bias at RHIC. Pairs of back-to-back high transverse momentum hadrons
are used for triggers to study associated hadron distributions. In contrast
with two- and three-particle correlations with a single trigger with similar
kinematic selections, the associated hadron distribution of both trigger sides
reveals no modification in either relative pseudo-rapidity or relative
azimuthal angle from d+Au to central Au+Au collisions. We determine associated
hadron yields and spectra as well as production rates for such correlated
back-to-back triggers to gain additional insights on medium properties.Comment: By the STAR Collaboration. 6 pages, 2 figure
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