bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface nanoscale periodic structures in congruent lithium niobate by domain reversal patterning and differential etching
Authors: Grilli Simonetta , Ferraro Pietro , De Natale Paolo , Tiribilli Bruno , Vassalli Massimo
Published: November 2005

We report on the fabrication and characterization of one- and two-dimensional periodic structures down to 200 nm size, in congruent lithium niobate crystal samples. Periods from 2μm to 530 nm are investigated. Interference photolithography is used to obtain short pitch insulating gratings, and subsequent electric-field poling, at the overpoling regime, is performed for periodic domain inversion. Nanoscale structures are obtained by selective chemical etching, and topographic investigations are performed by atomic force microscope. The fabricated structures are attractive in nonlinear optics for short-wavelength conversion and in the field of photonic crystals for Bragg and band-gap applications.
Picosecond carrier dynamics in AlInGaN multiple quantum wells
Authors: Hashemizadeh S. A. , Wells J.-P. R. , Murzyn P. , Brown J. , Jones B. D. , Wang T. , Parbrook P. J. , Fox A. M. , Mowbray D. J. , Skolnick M. S.
Published: November 2005

We report on measurements of stimulated emission in AlInGaN multiquantum wells using ultrafast pump-probe spectroscopy. Low power photoluminescence (PL) of Al0.04In0.015Ga0.945N∕Al0.12In0.01Ga0.87N multiquantum wells (MQW) yields a single MQW PL peak at 347.2 nm at 10 K. Wavelength degenerate pump-probe measurements show a single exponential decay at excitation densities below the stimulated emission threshold having a recombination decay constant of 160 ps at room temperature. At excitation densities greater than 50μJ∕cm2 a biexponential decay is observed, with a fast component (3.3 ps at Iexc=690μJ∕cm2) attributed to accelerated relaxation due to stimulated emission. The fractional strength of this fast component indicates that up to 85% of the excited carriers relax via stimulated emission.
Doubling the optical efficiency of a chiral liquid crystal laser using a reflector
Authors: Zhou Ying , Huang Yuhua , Rapaport Alexandra , Bass Michael , Wu Shin-Tson
Published: November 2005

A simple method for doubling the laser emission efficiency of Nd:yttrium-aluminum-garnet pumped cholesteric liquid crystal (CLC) photonic band edge lasers is demonstrated. By adding a mirror or a CLC reflector behind the dye-doped CLC cell, the lasing intensity is nearly doubled. For the mirror reflector, due to the mixing of right-handed and left-handed circular polarizations, the output laser is basically unpolarized. However, for the CLC reflector, a partially coherent laser can be built in which either right-handed or left-handed circularly polarized laser could dominate the output, depending on the handedness of the cholesteric structure.
Investigation of the probe-sample interaction in the ultrasonic/shear-force microscope: The phononic friction mechanism
Authors: Cui Xiquan , La Rosa Andres
Published: November 2005

The dissipative and conservative interactions between a sharp probe and a flat Si sample in the ultrasonic/shear-force microscope are investigated. It is shown that, when working in the ambient condition, there are two distinct probe-sample interaction regions: the pure dissipative interaction region in the relatively far probe-sample distance, and the highly correlated dissipative and conservative interaction region in the close probe-sample distance. The ultrasonic data suggest that the phonon generation is a dissipative channel for the probe-sample interaction in the shear force microscope. A shaking potential model is proposed to explain the phononic friction mechanism.
Role of ions in pool boiling heat transfer of pure and silica nanofluids
Authors: Milanova Denitsa , Kumar Ranganathan
Published: November 2005

Heat transfer in silica nanofluids at different acidity and base is measured for various ionic concentrations in a pool boiling experiment. Nanosilica suspension increases the critical heat flux 3 times compared to conventional fluids. The 10-nm particles possess a thicker double diffuse layer compared to 20-nm particles. The catalytic properties of nanofluids decrease in the presence of salts, allowing the particles to cluster and minimize the potential increase in heat transfer. Nanofluids in a strong electrolyte, i.e., in high ionic concentration, allow a higher critical heat flux than in buffer solutions because of the difference in surface area. The formation and surface structure of the deposition affect the thermal properties of the liquid.
Ambipolar organic thin-film transistors using C60/pentacene structure: Characterization of electronic structure and device property
Authors: Kang S. J. , Yi Y. , Kim C. Y. , Cho K. , Seo J. H. , Noh M. , Jeong K. , Yoo K.-H. , Whang C. N.
Published: November 2005

We fabricated ambipolar organic thin-film transistors (OTFTs) using C60 and pentacene. The electronic structure of the interface was investigated by using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy. The magnitude of the interface dipole and the band bendings at the interface was determined, and the complete energy level diagram for C60 on pentacene (C60/pentacene) was obtained. The lowered band offsets, due to the enhanced charge redistribution in C60/pentacene relative to pentacene on C60, are favorable for the ambipolar OTFTs. The measured field-effect mobilities were 0.017cm2∕Vs and 0.007cm2∕Vs for the p-channel and the n-channel operations, respectively. The threshold voltages were −2V for the p channel and 15.6V for the n channel, comparable to those of unipolar OTFTs using C60 or pentacene.
Domain distributions in tetragonal Pb(Zr,Ti)O3 thin films probed by polarized Raman spectroscopy
Authors: Osada Minoru , Nishida Ken , Wada Syunshuke , Okamoto Shoji , Ueno Risako , Funakubo Hiroshi , Katoda Takashi
Published: November 2005

We have investigated polarized Raman spectra of (001)/(100)-oriented tetragonal epitaxial Pb(ZrxTi1−x)O3 (PZT) thin films (x=∼0.35) in which the volume fraction of the polar c domain is systematically varied from 4% to 96%. From polarization analyses using high epitaxial quality films, we have successfully isolated the A1 and B1 phonons from the E phonons, thus offering a distinctive evaluation of the c domains. As increasing c-domain volume, the A1(TO) modes linearly increase in their intensity. A remarkable correlation is found between the A1(1TO)-mode intensity and the c-domain volume for PZT films. We suggest that this correlation as well as the A1(1TO)-mode intensity provide a simple and useful probe for characterization of c-domain volume and ferroelectric properties in PZT-based devices.
One THz harmonic oscillation of resonant tunneling diodes
Authors: Orihashi N. , Suzuki S. , Asada M.
Published: November 2005

One THz harmonic oscillation was observed in a sub-THz oscillating GaInAs∕AlAs resonant tunneling diode integrated with a slot antenna. The fundamental and third-harmonic frequencies were 342GHz and 1.02THz, respectively, for a 50μm long antenna. The maximum output power of the fundamental mode was around 23μW, and that of the third-harmonic component was 2.6% of the fundamental. Theoretical analysis with the van der Pole equation qualitatively explained the measured results.
Deep-level characterization of N-doped ZnO films prepared by reactive magnetron sputtering
Authors: Nakano Yoshitaka , Morikawa Takeshi , Ohwaki Takeshi , Taga Yasunori
Published: November 2005

We report on band gap states in N-doped ZnO (ZnO:N) films that were deposited on indium tin oxide/quartz substrates by reactive magnetron sputtering. Colored ZnO:N samples showed enhanced polycrystalline with increasing N-doping concentration, as determined by x-ray diffraction patterns. Deep-level optical spectroscopy measurements revealed three characteristic deep levels located at ∼0.98, ∼1.20, and ∼2.21eV below the conduction band. In particular, the pronounced 2.21eV band is newly introduced by the N doping and behaves as part of the valence band, resulting in band gap narrowing of ZnO. Therefore, this deep level is probably one origin of visible-light sensitivity in ZnO:N.
Atomic-scale mechanisms of selective adsorption and dimerization of pentacene on Si surfaces
Authors: Tsetseris L. , Pantelides S. T.
Published: November 2005

We report results of first-principles calculations in terms of which we elucidate the mechanisms for nucleation and initial growth of pentacene films on Si. Pentacene molecules bond in flat, distorted configurations on bare surfaces. On H-passivated surfaces, direct bonding or H replacement are not energetically favored. However, molecules bond in an upright configuration at isolated depassivated Si dangling bonds and film growth continues over the passivated area. The results elucidate generic adsorption issues on inert surfaces and suggest procedures for controlling film growth.
Structural properties and photoluminescence of zinc nitride nanowires
Authors: Zong Fujian , Ma Honglei , Ma Jin , Du Wei , Zhang Xijian , Xiao Hongdi , Ji Feng , Xue Chengshan
Published: November 2005

Zinc nitride nanowires can be synthesized by nitridation reaction of zinc powder with ammonia gas in 500ml∕min at the nitridation temperature of 600 °C for 120 min. Studies by using x-ray diffraction indicate that zinc nitride nanowires are cubic in structure with the lattice constant a=0.9788nm. Observations by using scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy show that zinc nitride is of nanowire structure. Typical room temperature photoluminescence spectrum of zinc nitride nanowires exhibits an ultraviolet emission peak at 385 nm (3.22 eV) and a blue emission band centered at 450 nm (2.76 eV).
Some New Luminance-Gradient Effects
Authors: Zavagno Daniele
Published: November 2005

Three compelling luminance-gradient effects are described. The first effect concerns a brightness enhancement and a luminous mist spreading out from a central area having the same luminance as the white background and surrounded by four rectangular inducers shaded with a linear luminance gradient. The second effect is perceived with a photographically reversed configuration, and concerns what may be considered a brightness reduction or the enhancement of a darkness quality of a target area of the visual scene. The third effect concerns the perception of a self-luminous disk inside a somewhat foggy medium. The effects are worthy of further examination because they challenge current theories of luminosity perception and brightness perception in general.
Perception of the Horizontal and Vertical in Tangible Displays: Minimal Gender Differences
Authors: Heller Morton A , Calcaterra Jeffrey A , Green Shavonda L , Barnette Stevette L
Published: November 2005

A study is reported of gender differences in a haptic version of three Piagetian tests that assess understanding of Euclidian space. A raised-line drawing kit was used both for subject responses and for production of stimuli. To test understanding of the horizontal, subjects felt pictures of a jar at four tilts and were asked to draw the water line. Two methods were used to examine understanding of the vertical. First, subjects drew a hanging electrical cord and light bulb, attached to the ceiling of a bus, parked on hills of four different angles. Subsequently, subjects drew telephone poles (represented by a single line) on hills of four different angles. In the jar task, males and females showed comparable performance, both groups showing large errors. Judgments of the vertical were very similar for males and females in the bus task, but errors diminished considerably for both genders when subjects drew telephone poles on hills. It is suggested that better judgments of the vertical in the pole task probably derive from the use of body-centered spatial reference information.
Constancy Scaling and Conflict When the Zöllner Illusion is Seen in Three Dimensions
Authors: Phillips David
Published: November 2005

If a standard Zöllner illusion is seen as a staircase in depth, pairs of long lines flanking convex stair edges appear to diverge as usual, but divergence in pairs flanking concave edges can appear reduced. If the stair is reversed perceptually in the manner of the Schroder staircase, convex and concave shapes exchange and the extent of apparent divergence in the long line pairs exchanges with them. The effect is enhanced if explicit stair edges are added, and reduced if the standard Zöllner pattern is replaced by one in which segments of the long lines are offset in the direction of the usual illusory effect. The observations suggest that the three-dimensional potential of the pattern cannot be excluded from explanations of the illusion, and are compatible with the view of Gregory and Harris that inappropriate constancy scaling is its primary cause, triggered ‘bottom – up’ by pattern properties or ‘top – down’ by cognitive inference. However, these two mechanisms would have to be acting in conflict to generate suppression of divergence in the concave steps. Pattern processing for properties, such as orientation, that are not associated with the potential of the Zöllner illusion as a three-dimensional configuration, but that have been suggested as sources of the illusion in recent studies, could also be acting in opposition to hypothesis scaling in the concave steps.
Exocentric Pointing in Three-Dimensional Space
Authors: Schoumans Nicole , van der Gon Jan J Denier
Published: November 2005

A study is reported of an exocentric pointing task in all three dimensions, in near space, with only two visible luminous objects—a pointer and a target. The task of the subject was to aim a pointer at a target. The results clearly show that visual space is not isotropic, since every set direction appeared to consist of two independent components—one in the projection onto a frontoparallel plane (tilt), the other in depth (slant). The tilt component shows a general trend across subjects, an oblique effect, and can be judged monocularly. The slant component is symmetrical in the mid-sagittal plane, requires the use of binocular information, and shows considerable differences between subjects. These differences seem to depend on the amount of binocular information used by each subject. There was a remarkably high level of consistency in the exocentric pointing, despite the absence of environmental cues. The within-subject consistency in the settings of the pointer corresponds to a consistency of about 1 min of arc in disparity of its tip, even though the pointer and target are separated by more than 5 deg.
Perceiving the Sweet Spot
Authors: Carello Claudia , Thuot Steve , Anderson Krista L , Turvey M T
Published: November 2005

Many sports involve aligning a hitting implement with a ball trajectory such that contact is made at the implement's center of percussion or ‘sweet spot’. This spot is not visibly distinct; its perception must be haptic. Although it is functionally defined with respect to contact—it is the point of impact that produces the least vibration in the hand holding the implement—hitting success requires appreciating the location of the sweet spot prior to contact. Two experiments verified that perceivers (novices as well as expert tennis players) distinguished perception of length from perception of the position of the sweet spot simply on the basis of wielding, both for tennis rackets and for bats contrived from wooden rods with attached masses. Results conformed to previous research on dynamic touch in showing that perceiving the lengths of wielded objects, including selectively perceiving partial lengths, is constrained by inertial properties of the object.
‘Coarse-to-Fine’ Cyclopean Processing
Authors: Popple Ariella V , Findlay John M
Published: November 2005

Previously (Popple et al, 1998 Vision Research38 319–326) we found, using random-dot stereograms, that initial vergence increases with the size of a cyclopean disc. A corresponding improvement in stereoacuity within the disc was predicted, because disparities in the disc would be brought closer to the plane of current fixation.

In the present experiment, we looked at the effect of the spatial extent of a briefly presented (≤ 500 ms) cyclopean depth pedestal on stereoacuity thresholds. Observers were required to judge the depth of a small, 1.7 deg, central disc relative to a larger surrounding disc in a random-pattern stereogram. The larger disc was set, initially, at a pedestal disparity of ±24 min of arc against a fixation-plane surround. The size of the larger disc was varied from 2.6 to 8.0 deg. As predicted, stereoacuity thresholds fell significantly with increasing pedestal disc size. Next, the disparity of the pedestal disc was varied. When pedestal disparity was reduced to ±2.4 min of arc, a disparity too small to demand vergence, the size effect disappeared except when the pedestal boundary was within 30 min of arc of the test disc boundary. We argue from this result that the effect was largely due to vergence and not cyclopean integration alone. However, the effect of pedestal size was found to persist with stimuli too brief to permit vergence (≤ 100 ms) suggesting that factors other than vergence may also play a role.
Stereoscopic Depth Cues Can Segment Motion Information
Authors: Snowden Robert J , Rossiter Melissa C
Published: November 2005

Can the motion system selectively process elements at a particular depth? We attempted to answer this question using global coherence tasks in which signal and noise elements could be given different disparities. In experiment 1 we found that, if all the signal elements had a disparity different from that of the noise elements, performance was far better than when they had the same disparity (at least for stereo-normal observers). In a second experiment we found that adding additional noise elements to the motion task had no effect if they had a different disparity (however, they had a marked effect for stereo-blind observers). We conclude that stereo disparity can be used as a segmentation cue by the motion system.
Visual Measurement of Relative Distances between Three Collinear Dots Rotating in a Slanted Plane
Authors: Wagemans Johan , Tibau Stefaan
Published: November 2005

Displays consisted of orthographic and perspective projections of three collinear dots rotating rigidly around a fixed centre in a plane slanted 45° in depth. Observers were asked to decide whether the middle of the three dots was exactly centred in 3-D space between the other two dots. The visible rotation segments were 120°, 160°, or 200° and the displacements were 2%, 4%, or 6%. Our untrained observers performed more poorly overall than well-practised observers tested earlier by Lappin and Fuqua (1983 Science221 480–482). Results of additional manipulations suggested that 2-D image properties played a more important role than acknowledged by Lappin and Fuqua. First, displacement size and the position of the rotation centre produced nonlinear effects. Second, the direction of displacement affected performance. Third, projection type and display type (static snapshots versus elliptic traces) were involved in complex interactions. Clearly, performance was affected by 2-D image properties that should be irrelevant to the calculation of 3-D projective invariants.
Some Recent Studies on the Extraretinal Contribution to Distance Perception
Authors: Mon-Williams Mark , Tresilian James R
Published: November 2005

Some recent studies on the extraretinal contribution to distance perception are reviewed. These experiments demonstrate that vergence can provide reliable information for judgments on the distance of proximal targets in the absence of all other cues. We argue that, although vergence is an unreliable cue at large fixation distances and is subject to a strong contraction bias when studied in isolation, these facts do not imply a minor role for vergence in near-space perception. When additional depth and distance cues are added, the contribution of vergence information becomes more complicated. We present results which indicate that the different cues to depth and distance are combined in a manner that can result in unexpected distortions of visual space. A simple heuristic model which can produce the observed distortions is outlined.
The Effects of Eccentricity and Vergence Angle upon the Relative Tilt of Corresponding Vertical and Horizontal Meridia Revealed Using the Minimum Motion Paradigm
Authors: Ledgeway Timothy , Rogers Brian J
Published: November 2005

When the corresponding horizontal meridia of the two eyes are aligned, the corresponding vertical meridia are tilted outwards in a temporal direction, a phenomenon first described by Helmholtz. However, it is not known if this effect is confined to the principal meridia or whether the same relationship exists between corresponding horizontal and corresponding vertical meridia at eccentric retinal locations. We sought to address this issue by exploiting the technique of Nakayama (1977 Proceedings of the Society of Photo-Optical Instrument Engineers120 2–9) in which the positions of alternating dichoptic images that produce minimal apparent motion were used to measure the relative tilt of corresponding meridia at a range of eccentricities up to ±16 deg away from the fovea. Stimuli were composed of dichoptic images, one containing a blank field and the other a pair of dots, which alternated at a rate of 0.63 Hz and the relative tilt (binocular orientation difference) between the pairs of dots presented to the two eyes was varied between ±11°. Nonius lines were used to maintain vergence angle, which was varied between 28 cm and infinity. Subjects judged which pair of alternating images produced the smallest amount of apparent motion (position change). It was found that at all eccentricities examined the corresponding horizontal meridia were generally aligned but the corresponding vertical meridia were consistently offset (extorted) by about ±2°. The tilts of corresponding principal meridia were typically unaffected when vergence angle was varied, indicating that little or no cyclovergence accompanied changes in horizontal vergence. The results suggest that the binocular correspondence system appears to be mapped by a horizontal shear distortion that extends to retinal locations at least as far as 16 deg away from the foveae. The invariant extorsion of corresponding principal vertical meridia with vergence state is consistent with previous suggestions that the empirical vertical horopter becomes progressively inclined with respect to the vertical as viewing distance increases.
Binocular and Monocular Detection of Gabor Patches in Binocular Two-Dimensional Noise
Authors: Pardhan Shahina , Rose David
Published: November 2005

Contrast thresholds for detecting sine-wave Gabor patches in two-dimensional externally added random-pixel noise were measured. Thresholds were obtained for monocular and binocular signals in the presence of spatial correlated (identical) and uncorrelated (independent) noise in the two eyes. Measurements were obtained at four different spectral densities of noise (including zero). Thresholds were higher for monocular stimuli than for binocular, and higher in the presence of correlated noise compared to uncorrelated noise. The magnitude of binocular summation, similar in correlated and uncorrelated noise, decreased with increasing noise strength. The independent contributions of internal noise and sampling efficiency to detection were analysed. Sampling efficiencies were higher for binocular than for monocular viewing for both types of noise, with values being higher with uncorrelated noise. Binocular stimuli showed a lower equivalent noise level compared to the mean monocular case for both types of noise.
Does Binocular Disparity Facilitate the Detection of Transparent Motion?
Authors: Hibbard Paul B , Bradshaw Mark F
Published: November 2005

Recent physiological studies have established that cortical cells that are tuned for the direction of motion may also exhibit tuning for binocular disparity. This tuning does not appear to provide any advantage in discriminating the direction of global motion in random-dot kinematograms. Here we investigated the possibility that this tuning may be important in the perception of transparent motion. Random-dot kinematograms were presented which contained coherent motion in a single direction or in two opposing directions. A greater proportion of signal dots was required for the detection of transparent motion than of motion in a single direction. This difference vanished when the two opposite directions of motion were presented with different disparities. These results suggest that the direction of global motion can be computed separately for surfaces which are clearly segregated in depth.
Visual Processing and Dyslexia
Authors: Everatt John , Bradshaw Mark F , Hibbard Paul B
Published: November 2005

Magnocellular-pathway deficits have been hypothesised to be responsible for the problems experienced by dyslexic individuals in reading. However, research has yet to provide a detailed account of the consequences of these deficits or to identify the behavioural link between them and reading disabilities. The aim of the present study was to determine the potential consequences of the magnocellular-pathway deficits for dyslexics in a comprehensive range of visual tasks. Dyslexics and nondyslexics were compared on their ability to (i) perform vernier-acuity and orientation-acuity tasks; (ii) perceive motion by using a range of measures common in the psychophysical literature ( Dmin, Dmax, and global coherence); and (iii) perceive shapes presented in random-dot stereograms at a range of disparity pedestals, thereby dissociating stereopsis from vergence control. The results indicated no significant differences in performance between the dyslexic and nondyslexic subjects in terms of the visual-acuity measures. In general, dyslexics performed relatively poorly on measures of motion perception and stereopsis, although when considered individually some of the dyslexics performed better than some of the controls. The poor performance of the dyslexics in the stereogram tasks was attributable to a subgroup of dyslexics who also appeared to have severe difficulty with the motion-coherence task. These data are consistent with previous evidence that some dyslexics may have deficits within the magnocellular visual pathway.
Estimator Reliability and Distance Scaling in Stereoscopic Slant Perception
Authors: Backus Benjamin T , Banks Martin S
Published: November 2005

When a horizontal or vertical magnifier is placed before one eye, a frontoparallel surface appears slanted. It appears slanted away from the eye with horizontal magnification (geometric effect) and toward the eye with vertical magnification (induced effect). According to current theory, the apparent slant in the geometric and induced effects should increase with viewing distance. The geometric effect does scale with distance, but there are conflicting reports as to whether the induced effect does. Ogle (1938 Archives of Ophthalmology20 604–623) reported that settings in slant-nulling tasks increase systematically with viewing distance, but Gillam et al (1988 Perception & Psychophysics44 473–483) and Rogers et al (1995 Perception24 Supplement, 33) reported that settings in slant-estimation tasks do not. We re-examined this apparent contradiction. First, we conducted two experiments whose results are consistent with the literature and thus replicate the apparent contradiction. Next, we analyzed the signals available for stereoscopic slant perception and developed a general model of perceived slant. The model is based on the assumption that the visual system knows the reliability of various slant-estimation methods for the viewing situation under consideration. The model's behavior explains the contradiction in the literature. The model also predicts that, by manipulating eye position, apparent slant can be made to increase with distance for vertical, but not for horizontal, magnification. This prediction was confirmed experimentally.
Coloured Overlays, Text, and Texture
Authors: Wilkins Arnold , Lewis Elizabeth
Published: November 2005

In four studies children were asked to read aloud a passage of randomly ordered common words with and without a coloured sheet of plastic (overlay) placed upon the page. The children's rate of reading increased with the overlay, for some children more than for others. The children were also asked to undertake a test of texture segmentation in which targets consisting of a structured texture had to be distinguished from within a random background texture. The texture segmentation was improved when the overlay was used, again for some children more than for others. The improvement in texture segmentation was, in general, correlated with the improvement in rate of reading. Slower readers were generally poorer at texture segmentation. The implications for reading, for texture segmentation, and for clinical tests of vision are discussed.
From Elements to Perception: Local and Global Processing in Visual Neurons
Authors: Spillmann Lothar
Published: November 2005

Gestalt psychologists in the early part of the century challenged psychophysical notions that perceptual phenomena can be understood from a punctate (atomistic) analysis of the elements present in the stimulus. Their ideas slowed later attempts to explain vision in terms of single-cell recordings from individual neurons. A rapprochement between Gestalt phenomenology and neurophysiology seemed unlikely when the first ECVP was held in Marburg, Germany, in 1978. Since that time, response properties of neurons have been discovered that invite an interpretation of visual phenomena (including illusions) in terms of neuronal processing by long-range interactions, as first proposed by Mach and Hering in the last century.

This article traces a personal journey into the early days of neurophysiological vision research to illustrate the progress that has taken place from the first attempts to correlate single-cell responses with visual perceptions. Whereas initially the receptive-field properties of individual classes of cells—eg contrast, wavelength, orientation, motion, disparity, and spatial-frequency detectors—were used to account for relatively simple visual phenomena, nowadays complex perceptions are interpreted in terms of long-range interactions, involving many neurons. This change in paradigm from local to global processing was made possible by recent findings, in the cortex, on horizontal interactions and backward propagation (feedback loops) in addition to classical feedforward processing. These mechanisms are exemplified by studies of the tilt effect and tilt aftereffect, direction-specific motion adaptation, illusory contours, filling-in and fading, figure – ground segregation by orientation and motion contrast, and pop-out in dynamic visual-noise patterns. Major questions for future research and a discussion of their epistemological implications conclude the article.
Demonstrating the Temporal Modulation Transfer Function
Authors: Anstis Stuart , Kontsevich Leonid , Tyler Christopher
Published: November 2005

A 120-frame movie, which can be downloaded from specified web sites, allows an observer to see the qualitative form of his or her temporal modulation transfer function. Results collected from two of the authors are presented.
What is the Speed of Transparent and Kinetic-Boundary Displays?
Authors: De Bruyn Bart , Orban Guy A
Published: November 2005

To compare transparent motion and kinetic boundaries with unidirectional motion, in many studies the relative motion is generated by superimposing or adjoining unidirectional motions oriented in opposite directions. The presumption, tacitly underlying this comparison, is that the two oppositely directed velocities are independent of one another as far as their speed is concerned, ie the speed of the relative motion is presumed to be equivalent to the speed of the unidirectional components. Here we report that the relative motion between dots moving in opposite directions augments perceived speed. A constant-stimuli procedure was used to pair transparent-motion or kinetic-boundary displays with unidirectional motion, and human observers were asked to match the speed of the relative and unidirectional motions. The results show that transparency and kinetic boundaries increase the perceived visual speed by about 50%, compared with the speed of the individual components.
Thompson's Margaret Thatcher Illusion: When Inversion Fails
Authors: Rakover Sam S
Published: November 2005

It is argued that the whole face is more dominant than the individual features. In the case of a jumbled face the external pattern is dominant when a face is upright, whereas the internal pattern is dominant when a face is inverted.
Disparity Minimisation, Cyclovergence, and the Validity of Nonius Lines as a Technique for Measuring Torsional Alignment
Authors: Rogers Brian J , Bradshaw Mark F
Published: November 2005

Frisby et al (1993 Perception22 Supplement, 115) proposed that the visual system might make cyclovergent eye movements in order to minimise the overall pattern of both vertical and horizontal disparities when an observer views an inclined stereoscopic surface. Their measurements of cyclovergence, which used vertically oriented nonius lines, were found to be consistent with that proposal. In our experiment 1, we measured torsional eye movements objectively, using scleral coils, and found no evidence of a cyclovergent response to either a real inclined surface or to a simulated inclined surface in which the two stereoscopic images were related by a horizontal shear transformation. These results are inconsistent with the disparity minimisation hypothesis. In order to account for the discrepant findings of the two studies, we propose that vertically oriented nonius lines may not be a valid method for assessing cyclovergence because the lines can be seen as lying ‘within’ the inclined surface. In experiment 2, we tested the predictions of the cyclovergence hypothesis of Frisby et al against our own ‘within surface’ explanation, using both horizontally and vertically oriented nonius lines and dichoptic images related by either a horizontal or a vertical shear. If cyclovergence were the cause of the misalignment, both horizontal and vertical nonius lines should appear misaligned to the same extent. This was not found to be the case. We conclude that vertical nonius lines may not be a valid technique for measuring cyclovergence when the lines are seen against a background of an inclined surface.
Steering, Optic Flow, and the Respective Importance of Depth and Retinal Motion Distribution
Authors: Rushton Simon K , Harris Julie M , Wann John P
Published: November 2005

Movement through an environment produces an optical spatiotemporal pattern, known as a flow field. When visually guiding movement using a flow field, do humans make use of information about the distance of constituent elements? Employing a novel active steering task, we examined the use of depth (height-in-scene and disparity) and the role of the retinal motion distribution in the perceptual control of heading from flow. We found that retinal motion distribution, rather than depth order, has the primary role in determining the accuracy of steering.
More about Brows: How Poses That Change Brow Position Affect Perceptions of Gender
Authors: Campbell Ruth , Benson Philip J , Wallace Simon B , Doesbergh Suzanne , Coleman Michael
Published: November 2005

The speeded categorisation of gender from photographs of men's and women's faces under conditions of vertical brow and vertical head movement was explored in two sets of experiments. These studies were guided by the suggestion that a simple cue to gender in faces, the vertical distance between the eyelid and brow, could support such decisions. In men this distance is smaller than in women, and can be further reduced by lowering the brows and also by lowering the head and raising the eyes to camera. How does the gender-classification mechanism take changes in pose into account? Male faces with lowered brows (experiment 1) were more quickly and accurately categorised (there was little corresponding ‘feminisation’ of raised-brow faces). Lowering gaze had a similar effect, but failed to interact with head lowering in a simple manner (experiment 2). We conclude that the initial classification of gender from the facial image may not involve normalisation of the face image to a canonical state (the ‘mug-shot view’) for expressive pose (brow movement and direction of gaze). For head pose (relative position of the features when the face is not viewed head-on), normalisation cannot be ruled out. Some perceptual mechanisms for these effects, and their functional implications, are discussed.
Preferences in Quadrangles Reconsidered
Authors: Ohta Hirohiko
Published: November 2005

Through about 130 years of the history of experimental aesthetics, preferences of figures have been summarized in representative values such as the golden ratio. Researches especially in the golden-section hypothesis overshadowed the basic and profound problem of how people's individual preference would be decided. In the present study I returned to simple quadrangles, and investigated each person's subjective preferences by a production method, recording eye movements, and having qualitative interviews. Two basic scanning patterns on quadrangles emerged through the analysis of eye movements, and more complicated patterns were made by various combinations of these two. The distribution of subjects' preferred proportions showed that squares and square-like quadrangles were chosen most frequently, although the average of height/width ratios came close to the golden ratio in most quadrangle types. The results of interviews revealed various characteristics of decision processes of preferred shapes in the subjects. A discussion is provided on dealing with the golden ratio, and the importance of studying subjects' processes of preferences is proposed for the future of empirical aesthetics.
Effects of Similarity on Apparent Motion and Perceptual Grouping
Authors: Oyama Tadasu , Simizu Masako , Tozawa Junko
Published: November 2005

Effects of similarity in colour, luminance, size, and shape on apparent motion and perceptual grouping were examined in part 1 in two parallel experiments on the same seven subjects. In both experiments, the effect of similarity was compared with that of proximity in competitive, bistable stimulus situations. A combination of a larger horizontal separation between the homogeneous stimulus elements and a smaller constant vertical separation between heterogeneous stimulus elements produced two kinds of apparent motion (or perceptual grouping) with equal probabilities. Such matched separations between homogeneous stimulus elements were obtained by the double staircase method in various stimulus conditions. In both experiments on apparent motion and perceptual grouping matched separation was found to increase as the difference between the heterogeneous stimulus elements increased. High correlations (0.71 to 0.94) of matched separations were found between apparent motion and perceptual grouping in four stimulus series: colour, luminance, size, and shape. Six of the seven subjects were also tested in part 2. Here, the effects of differences were found to work additively across different perceptual attributes in both phenomena, when multiple differences were combined in heterogeneous elements. The experimental results are discussed from the point of view that apparent motion is an example of perceptual constancy.
Effects of Similarity in Bandwidth on the Auditory Sequential Streaming of Two-Tone Complexes
Authors: Cusack Rhodri , Roberts Brian
Published: November 2005

We investigated the perceptual grouping of sequentially presented sounds—auditory stream segregation. It is well established that sounds heard as more similar in quality, or timbre, are more likely to be grouped into the same auditory stream. However, it is often unclear exactly what acoustic factors determine timbre. In this study, we presented various sequences of simple sounds, each comprising two frequency components (two-tone complexes), and measured their perceptual grouping. We varied only one parameter between trials, the intercomponent separation for some of the complexes, and examined the effects on stream segregation. Four hypotheses are presented that might predict the extent of streaming. Specifically, least streaming might be expected when the sounds were most similar in either (1) the frequency regions in which they have energy (maximum spectral overlap), (2) their auditory bandwidths, (3) their relative bandwidths, or (4) the rate at which the two components beat together (intermodulation rate). It was found that least streaming occurred when sounds were most similar in either their auditory or their relative bandwidths. Although these two hypotheses could not be distinguished, the results were clearly different from those predicted by hypotheses (1) and (4). The implications for models of stream segregation are discussed.
The Effect of Marker Frequency Disparity on the Discrimination of Gap Duration in Monkeys
Authors: Izumi Akihiro
Published: November 2005

Duration-discrimination thresholds of the silent interval (gap) between two successive tones (markers) were measured in four Japanese monkeys. The task was serial discrimination, and monkeys were required to release the lever when the gap duration decreased from 200 ms. Monkeys successfully acquired the task, and gap thresholds of monkeys were revealed to be larger than previous data with human subjects. Gap thresholds were not affected by marker frequency when the two markers were identical in frequency, though the thresholds increased when large frequency differences existed between markers. The effect of marker frequency disparity on gap thresholds in monkeys is discussed in terms of the difficulty in integrating information from discrete frequency channels.
Selective Peripheral Fading: Evidence for Inhibitory Sensory Effect of Attention
Authors: Lou Lianggang
Published: November 2005

A circular array of six discs, three green and three orange in alternate positions, was presented against a uniform grey background. Sixteen observers maintained steady fixation at the centre of the array, and were instructed to direct their attention to three discs of one colour and to ignore the three discs of the other colour. In about 10 s (mean = 11.35 s), some discs started to fade away from awareness. Of those starting to fade, most (mean = 81.3%) were those selected for attention. The faded discs remained out of awareness for up to a few seconds (mean = 1.55 s) during which other discs were clearly visible. The fading increased with eccentricity, a defining characteristic of Troxler fading. However, the selectivity of the fading strongly suggests that voluntary attention can have an inhibitory effect on early sensory processing. Were the fading entirely due to local sensory adaptation, the unattended stimuli would have to be equally adapted and yet somehow remain visible for seconds, which is not plausible.
Trends in European Visual Science: 1978–1997
Authors: Cavonius C R
Published: November 2005

European visual science during the past 20 years—with the glaring exception of ophthalmological research—is reflected in the annual programmes of the European Conference on Visual Perception. The number of countries that have participated has increased with time, and the spectrum of topics that have been presented has broadened. The number of multiple-author papers has increased dramatically, as has the number of papers by authors from different institutions and different countries.
The Peripheral Drift Illusion: A Motion Illusion in the Visual Periphery
Authors: Faubert Jocelyn , Herbert Andrew M
Published: November 2005

Circularly repeating patches containing sawtooth luminance gradients produce a sensation of motion when viewed in the periphery. Illusory motion is perceived in a dark-to-light direction, but only when one's gaze is directed to different locations around the stimulus, a point outside the display is fixated and the observer blinks, or when the stimulus is sequentially displayed at different locations whilst the observer fixates one point. We propose that the illusion is produced by the interaction of three factors: (i) introducing transients as a result of eye movements or blinks; (ii) differing latencies in the processing of luminance; and (iii) spatiotemporal integration of the differing luminance signals in the periphery.
Color Filling-in under Steady Fixation: Behavioral Demonstration in Monkeys and Humans
Authors: Friedman Howard S , Zhou Hong , von der Heydt Rüdiger
Published: November 2005

Color filling-in is a phenomenon in which the color of an object appears to be filled-in by the color of the surrounding field. We have studied the question of whether monkeys perceive color filling-in with near-foveal stimuli under steady fixation. Two monkeys were trained to fixate steadily and to attend to a disk, surrounded by an annulus of the complementary color, in parafoveal vision. Using displays in which the color of the disk was gradually changed to that of the annulus, we trained the animals to signal when they perceived a uniform color field. During the experiment, we introduced a small percentage of trials in which the disk color remained constant, and looked for ‘filling-in’ responses in these trials. Three human subjects were also tested for comparison. All subjects produced ‘filling-in’ responses with frequencies that were significantly higher for static disks with blurred borders than for moving disks or disks with sharp borders. This indicates that the monkeys' responses reflected perceptual filling-in, rather than random behavior. The time course of filling-in was similar in monkeys and humans. For the blurred static disks, responses occurred first after 3–4 s of fixation, reaching a probability of 0.2–0.8 by the end of 6 s, depending on the subject.
Photopic Visual Phantom Illusion: Its Common and Unique Characteristics as a Completion Effect
Authors: Kitaoka Akiyoshi , Gyoba Jiro , Kawabata Hideaki
Published: November 2005

An illusion similar to the stationary visual phantom illusion presented earlier by Gyoba (1983, Vision Research23 205–211) is reported. This illusion is visible in photopic vision and we have tentatively named it the ‘photopic phantom illusion’. A typical example of this illusion is a white and light-gray square-wave grating occluded by a black region. In this figure, a phantom grating running across the occluder with clear contours but less contrast, is seen. The critical spatial frequencies of photopic phantoms have been measured and compared with those of scotopic phantoms that have been reported previously, revealing a great resemblance between them. We discuss the characteristics of this illusion in terms of transparency, stereoscopic viewing, and perceptual completion.