149,424 research outputs found
Oculomotor examination of the weapon focus effect: does a gun automatically engage visual attention?
A person is less likely to be accurately remembered if they appear in a visual scene with a gun, a result that has been termed the weapon focus effect (WFE). Explanations of the WFE argue that weapons engage attention because they are unusual and/or threatening, which causes encoding deficits for the other items in the visual scene. Previous WFE research has always embedded the weapon and nonweapon objects within a larger context that provides information about an actor's intention to use the object. As such, it is currently unknown whether a gun automatically engages attention to a greater extent than other objects independent of the context in which it is presente
Finding any Waldo: zero-shot invariant and efficient visual search
Searching for a target object in a cluttered scene constitutes a fundamental
challenge in daily vision. Visual search must be selective enough to
discriminate the target from distractors, invariant to changes in the
appearance of the target, efficient to avoid exhaustive exploration of the
image, and must generalize to locate novel target objects with zero-shot
training. Previous work has focused on searching for perfect matches of a
target after extensive category-specific training. Here we show for the first
time that humans can efficiently and invariantly search for natural objects in
complex scenes. To gain insight into the mechanisms that guide visual search,
we propose a biologically inspired computational model that can locate targets
without exhaustive sampling and generalize to novel objects. The model provides
an approximation to the mechanisms integrating bottom-up and top-down signals
during search in natural scenes.Comment: Number of figures: 6 Number of supplementary figures: 1
Decoupling heavy sparticles in Effective SUSY scenarios: Unification, Higgs masses and tachyon bounds
Using two-loop renormalization group equations implementing the decoupling of
heavy scalars, Effective SUSY scenarios are studied in the limit in which there
is a single low energy Higgs field. Gauge coupling unification is shown to hold
with similar or better precision than in standard MSSM scenarios. b-tau
unification is examined, and Higgs masses are computed using the effective
potential, including two-loop contributions from scalars. A 125 GeV Higgs is
compatible with stops/sbottoms at around 300 GeV with non-universal boundary
conditions at the scale of the heavy sparticles if some of the trilinear
couplings at this scale take values of the order of 1-2 TeV; if more
constrained boundary conditions inspired by msugra or gauge mediation are set
at a higher scale, heavier colored sparticles are required in general. Finally,
since the decoupled RG flow for third-generation scalar masses departs very
significantly from the MSSM DR-bar one, tachyon bounds for light scalars are
revisited and shown to be relaxed by up to a TeV or more.Comment: 35 pages, 17 figures. v2: Updated some scans, allowing for changes in
sign of some parameters, minor improvements. v3: Typos corrected in formulae
in the appendices, added some clarifying remarks about flavor mixing being
ignore
Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect and Raman spectroscopy
The electronic properties of graphene nano-flakes (GNFs) with different edge
passivation is investigated by using density functional theory. Passivation
with F and H atoms are considered: C X (X=F or H). We studied
GNFs with and limit ourselves to the lowest energy configurations.
We found that: i) the energy difference between the highest occupied
molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)
decreases with , ii) topological defects (pentagon and heptagon) break the
symmetry of the GNFs and enhance the electric polarization, iii) the mutual
interaction of bilayer GNFs can be understood by dipole-dipole interaction
which were found sensitive to the relative orientation of the GNFs, iv) the
permanent dipoles depend on the edge terminated atom, while the energy gap is
independent of it, and v) the presence of heptagon and pentagon defects in the
GNFs results in the largest difference between the energy of the spin-up and
spin-down electrons which is larger for the H-passivated GNFs as compared to
F-passivated GNFs. Our study shows clearly the effect of geometry, size,
termination and bilayer on the electronic properties of small GNFs.This study
reveals important features of graphene nano-flakes which can be detected using
Raman spectroscopy.Comment: 23 pages, 14 figures, accepted in J. Chem. Phy
What we observe is biased by what other people tell us: beliefs about the reliability of gaze behavior modulate attentional orienting to gaze cues
For effective social interactions with other people, information about the physical environment must be integrated with information about the interaction partner. In order to achieve this, processing of social information is guided by two components: a bottom-up mechanism reflexively triggered by stimulus-related information in the social scene and a top-down mechanism activated by task-related context information. In the present study, we investigated whether these components interact during attentional orienting to gaze direction. In particular, we examined whether the spatial specificity of gaze cueing is modulated by expectations about the reliability of gaze behavior. Expectations were either induced by instruction or could be derived from experience with displayed gaze behavior. Spatially specific cueing effects were observed with highly predictive gaze cues, but also when participants merely believed that actually non-predictive cues were highly predictive. Conversely, cueing effects for the whole gazed-at hemifield were observed with non-predictive gaze cues, and spatially specific cueing effects were attenuated when actually predictive gaze cues were believed to be non-predictive. This pattern indicates that (i) information about cue predictivity gained from sampling gaze behavior across social episodes can be incorporated in the attentional orienting to social cues, and that (ii) beliefs about gaze behavior modulate attentional orienting to gaze direction even when they contradict information available from social episodes
Movement in cluttered virtual environments
Imagine walking around a cluttered room but then having little idea of where you have traveled. This frequently happens when people move around small virtual environments (VEs), searching for targets. In three experiments, participants searched small-scale VEs using different movement interfaces, collision response algorithms, and fields of view. Participants' searches were most efficient in terms of distance traveled, time taken, and path followed when the simplest form of movement (view direction) was used in conjunction with a response algorithm that guided ("slipped") them around obstacles when collisions occurred. Unexpectedly, and in both immersive and desktop VEs, participants often had great difficulty finding the targets, despite the fact that participants could see the whole VE if they stood in one place and turned around. Thus, the trivial real-world task used in the present study highlights a basic problem with current VE systems
Clearing Contamination in Large Networks
In this work, we study the problem of clearing contamination spreading
through a large network where we model the problem as a graph searching game.
The problem can be summarized as constructing a search strategy that will leave
the graph clear of any contamination at the end of the searching process in as
few steps as possible. We show that this problem is NP-hard even on directed
acyclic graphs and provide an efficient approximation algorithm. We
experimentally observe the performance of our approximation algorithm in
relation to the lower bound on several large online networks including
Slashdot, Epinions and Twitter. The experiments reveal that in most cases our
algorithm performs near optimally
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