Spatial distortion induced by imperceptible visual stimuli

Previous studies have explored the effects of attention on spatial representation. Specifically, in the attentional repulsion effect, a transient visual cue that captures attention has been shown to alter the perceived position of a target stimulus to the direction away from the cue. The effect is also susceptible to retrospective influence, that attention appears to attract the target when the cue appears afterwards. This study examined the necessity of visual awareness of the cue in these phenomena. We found that when the cues were rendered invisible by backward visual masks, both repulsion and attraction effects were weakened but still observed. The results suggest that the effects possibly depend on processes that are not necessarily associated with conscious visual awareness of the cues. We conjecture that attentional shift produced by the weak, invisible cues may play a role in spatial distortion; but other possible accounts including non-attentional ones are also discussed.     

Texture and grain boundary character distribution (GBCD) in rapidly solidified and annealed Fe–6·5 mass% Si ribbons

Abstract

The type and frequency of grain boundaries, the so-called grain boundary character distribution (GBCD), has been determined in rapidly solidified and subsequently annealed Fe-6·5 mass% Si alloy ribbon by the scanning electron microscopy-electron channelling pattern (SEM-ECP) technique. High frequencies of low-angle boundaries and coincidence boundaries with Σ3, Σ9, Σ11, Σ17 and Σ19 were observed in a fully annealed ribbon with well defined {110} texture. The total frequency of low-angle boundaries and coincidence boundaries is almost one-half of all grain boundaries. The coincidence boundaries which occurred more frequently are exactly those predicted theoretically from the coincidence orientations for 〈110〉 rotation in cubic crystals, similar to those observed previously in {100} textured ribbons of the same alloy produced by the same processing method. The presence of a close relationship between the type of texture and GBCD has been confirmed by experiment on differently textured ribbons of the same material.     

Visualization of stress distribution using mechanoluminescence from Sr3Al2O6: Eu and the nature of the luminescence mechanism

We have investigated the dependence of the mechanoluminescence intensity from Sr3Al2O6: Eu on compressive stress. The distribution of the mechanoluminescence intensity, which is clearly visible to the naked eye, is consistent with the calculated stress distribution. The luminescence centre has been identified as the Eu2+ ion from spectra of the mechanoluminescence and also from photoluminescence studies of Sr3Al2O6: Eu. The mechanoluminescence intensity decreases on repetitive application of stress but recovers completely on irradiation with ultraviolet light. The Sr3Al2O6: Eu is a p-type semiconductor and has hole traps of depth 0.11 eV. It is suggested that the mechanoluminescence mechanism arises from the movement of dislocations and recombination between electrons and holes released from these traps which are associated with Eu2+ centres.     

Evolution of a sharp {110} texture in microcrystalline Fe78Si9B13 during magnetic crystallization from the amorphous phase

The effect of magnetic crystallization on texture evolution and control in nanocrystalline materials has been studied using a melt-spun amorphous Fe₇₈Si₉B₁₃ alloy. The magnetic crystallization was conducted at temperatures ranging from 653 to 853?K in a magnetic field up to 6?T. The temperatures used for magnetic crystallization were chosen on the basis of the Curie and crystallization temperatures of the amorphous phase, and the Curie temperature of the crystallized phase. The resultant microstructure was characterized by X-ray diffraction and FE-SEM/EBSP/OIM techniques. It was found that a sharp {110} texture developed when the amorphous precursor was crystallized at 853?K in a magnetic field of 6?T applied in a direction parallel to the ribbon surface.     

The fractal property of internal structure of facial affect recognition: A complex system approach

Based on a circumplex model of facial affect, four inner affective circumplexes, assumed to have 100%, 75%, 50%, and 25% emotional intensities, were investigated in terms of fractal, which is a concept of complex systems. Results revealed that the perimeters of the circumplex excluding the 25% condition possessed fractal property characterised by features specific to fractals. Results also showed that fractal dimension in the 50% condition (1.58 dimension) was significantly higher than that in the 100% (1.45 dimension) and 75% (1.45 dimension) conditions, indicating that the cognitive structure of facial affect in the 50% condition was more complex than that in the 100% and 75% conditions.     

Is memory for plans unique? a study using common nouns as stimuli

The present study explored the question of whether the U-shape effect, which was observed in previous experiments on memory for fictitious plans is unique to the memory for plans or not, i.e., are plans for the morning and for the evening recalled better than those for the afternoon. To investigate we used a "common noun" as the material to be memorized instead of the "action phrase" as used in Watanabe and Kawaguchi's earlier experiments. Free recall tasks were performed in two experiments: in Exp. 1, a sample of 15 undergraduates memorized "hour" and "common noun" pairs, while in Exp. 2 another 15 undergraduates memorized "number" and "common noun" pairs. The results of these experiments indicated no significant effect for time of day. This suggests that the U-shape effect observed in Watanabe and Kawaguchi's experiments, in which participants were asked to memorize a combination of an "hour" and an "action phrase" is unique to memory for plans.     

Visual grouping by motion precedes the relative localization between moving and flashed stimuli

A flashed stimulus is perceived as spatially lagging behind a moving stimulus when they are spatially aligned. When several elements are perceptually grouped into a unitary moving object, a flash presented at the leading edge of the moving stimulus suffers a larger spatial lag than a flash presented at the trailing edge (K. Watanabe. R. Nijhawan. B. Khurana, & S. Shimojo. 2001). By manipulation of the flash onset relative to the motion onset, the present study investigated the order of perceptual operations of visual motion grouping and relative visual localization. It was found that the asymmetric mislocalization was observed irrespective of physical and/or perceptual temporal order between the motion and flash onsets. Thus, grouping by motion must be completed to define the leading-trailing relation in a moving object before the visual system explicitly represents the relative positions of moving and flashed stimuli.     

Neural mechanisms of spatial working memory: Contributions of the dorsolateral prefrontal cortex and the thalamic mediodorsal nucleus

The dorsolateral prefrontal cortex (DLPFC) has been known to play an important role in working memory. Neurophysiological studies have revealed that delay period activity observed in the DLPFC is a neural correlate of the temporary storage mechanism for information and that this activity represents either retrospective or prospective information, although the majority represents retrospective information. However, the DLPFC is not the only brain area related to working memory. The analysis of neural activity in the thalamic mediodorsal (MD) nucleus reveals that the MD also participates in working memory. Although similar task-related activities were observed in the MD, the directional bias of these activities and the proportion of presaccadic activity are different between the MD and the DLPFC. These results indicate that, although the MD participates in working memory, the way it participates in this process is different between these two areas, in that the MD participates more in motor control aspects than the DLPFC does.     

Attentional set for axis of symmetry in symmetry-defined visual search

Olivers and van der Helm (1998) showed that symmetry-defined visual search (for both symmetry and asymmetry) requires selective spatial attention. We hypothesize that an attentional set for the orientation of a symmetry axis also is involved in symmetry-defined visual search. We conducted three symmetry-defined visual search experiments with manipulations of the axis of symmetry orientations, and performance was better when the axis orientations within the search array were uniform, rather than a mixture of two orientations, and the attentional set for the axis orientation could be kept. In addition, search performance when the target was defined by the presence of symmetry was equivalent to that when the target was defined by a difference of symmetry axis orientation. These results suggest that attentional set for axis orientation plays a fundamental role in symmetry-defined visual search.     

Object-based anisotropies in the flash-lag effect

The relative visual position of a briefly flashed stimulus is systematically modified in the presence of motion signals. We investigated the two-dimensional distortion of the positional representation of a flash relative to a moving stimulus. Analysis of the spatial pattern of mislocalization revealed that the perceived position of a flash was not uniformly displaced, but instead shifted toward a single point of convergence that followed the moving object from behind at a fixed distance. Although the absolute magnitude of mislocalization increased with motion speed, the convergence point remained unaffected. The motion modified the perceived position of a flash, but had little influence on the perceived shape of a spatially extended flash stimulus. These results demonstrate that motion anisotropically distorts positional representation after the shapes of objects are represented. Furthermore, the results imply that the flash-lag effect may be considered a special case of two-dimensional anisotropic distortion.