Attentional capture by entirely irrelevant distractors

Studies of attentional capture often question whether an irrelevant distractor will capture attention or be successfully ignored (e.g., Folk & Remington, 1998). Here we establish a new measure of attentional capture by distractors that are entirely irrelevant to the task in terms of visual appearance, meaning, and location (colourful cartoon figures presented in the periphery while subjects perform a central letter-search task). The presence of such a distractor significantly increased search RTs, suggesting it captured attention despite its task-irrelevance. Such attentional capture was found regardless of whether the search target was a singleton or not, and for both frequent and infrequent distractors, as well as for meaningful and meaningless distractor stimuli, although the cost was greater for infrequent and meaningful distractors. These results establish stimulus-driven capture by entirely irrelevant distractors and thus provide a demonstration of attentional capture that is more akin to distraction by irrelevant stimuli in daily life

A Blind Search for Magnetospheric Emissions from Planetary Companions to Nearby Solar-type Stars

This paper reports a blind search for magnetospheric emissions from planets around nearby stars. Young stars are likely to have much stronger stellar winds than the Sun, and because planetary magnetospheric emissions are powered by stellar winds, stronger stellar winds may enhance the radio luminosity of any orbiting planets. Using various stellar catalogs, we selected nearby stars (<~ 30 pc) with relatively young age estimates (< 3 Gyr). We constructed different samples from the stellar catalogs, finding between 100 and several hundred stars. We stacked images from the 74-MHz (4-m wavelength) VLA Low-frequency Sky Survey (VLSS), obtaining 3\sigma limits on planetary emission in the stacked images of between 10 and 33 mJy. These flux density limits correspond to average planetary luminosities less than 5--10 x 10^{23} erg/s. Using recent models for the scaling of stellar wind velocity, density, and magnetic field with stellar age, we estimate scaling factors for the strength of stellar winds, relative to the Sun, in our samples. The typical kinetic energy carried by the stellar winds in our samples is 15--50 times larger than that of the Sun, and the typical magnetic energy is 5--10 times larger. If we assume that every star is orbited by a Jupiter-like planet with a luminosity larger than that of the Jovian decametric radiation by the above factors, our limits on planetary luminosities from the stacking analysis are likely to be a factor of 10--100 above what would be required to detect the planets in a statistical sense. Similar statistical analyses with observations by future instruments, such as the Low Frequency Array (LOFAR) and the Long Wavelength Array (LWA), offer the promise of improvements by factors of 10--100.Comment: 11 pages; AASTeX; accepted for publication in A

Competition between auditory and visual spatial cues during visual task performance

There is debate in the crossmodal cueing literature as to whether capture of visual attention by means of sound is a fully automatic process. Recent studies show that when visual attention is endogenously focused sound still captures attention. The current study investigated whether there is interaction between exogenous auditory and visual capture. Participants preformed an orthogonal cueing task, in which, the visual target was preceded by both a peripheral visual and auditory cue. When both cues were presented at chance level, visual and auditory capture was observed. However, when the validity of the visual cue was increased to 80% only visual capture and no auditory capture was observed. Furthermore, a highly predictive (80% valid) auditory cue was not able to prevent visual capture. These results demonstrate that crossmodal auditory capture does not occur when a competing predictive visual event is presented and is therefore not a fully automatic process

Visual onset expands subjective time

We report a distortion of subjective time perception in which the duration of a first interval is perceived to be longer than the succeeding interval of the same duration. The amount of time expansion depends on the onset type defining the first interval. When a stimulus appears abruptly, its duration is perceived to be longer than when it appears following a stationary array. The difference in the processing time for the stimulus onset and motion onset, measured as reaction times, agrees with the difference in time expansion. Our results suggest that initial transient responses for a visual onset serve as a temporal marker for time estimation, and a systematic change in the processing time for onsets affects perceived time

Surveying the Dynamic Radio Sky with the Long Wavelength Demonstrator Array

This paper presents a search for radio transients at a frequency of 73.8 MHz (4 m wavelength) using the all-sky imaging capabilities of the Long Wavelength Demonstrator Array (LWDA). The LWDA was a 16-dipole phased array telescope, located on the site of the Very Large Array in New Mexico. The field of view of the individual dipoles was essentially the entire sky, and the number of dipoles was sufficiently small that a simple software correlator could be used to make all-sky images. From 2006 October to 2007 February, we conducted an all-sky transient search program, acquiring a total of 106 hr of data; the time sampling varied, being 5 minutes at the start of the program and improving to 2 minutes by the end of the program. We were able to detect solar flares, and in a special-purpose mode, radio reflections from ionized meteor trails during the 2006 Leonid meteor shower. We detected no transients originating outside of the solar system above a flux density limit of 500 Jy, equivalent to a limit of no more than about 10^{-2} events/yr/deg^2, having a pulse energy density >~ 1.5 x 10^{-20} J/m^2/Hz at 73.8 MHz for pulse widths of about 300 s. This event rate is comparable to that determined from previous all-sky transient searches, but at a lower frequency than most previous all-sky searches. We believe that the LWDA illustrates how an all-sky imaging mode could be a useful operational model for low-frequency instruments such as the Low Frequency Array, the Long Wavelength Array station, the low-frequency component of the Square Kilometre Array, and potentially the Lunar Radio Array.Comment: 20 pages; accepted for publication in A