Speed discrimination of stereoscopic (cyclopean) motion

This study investigated the degree to which speed of stereoscopic translational motion (i.e. moving binocular disparity information) can be discriminated in a display that minimizes position information. Observers viewed dynamic random-element stereograms depicting arrays of randomly positioned stereoscopic dots that moved bidirectionally. Two tasks were performed: a speed discrimination task and a displacement discrimination task. Across a range of conditions, speed could be discriminated under conditions in which displacement could not. Thus, speed of stereoscopic motion can be discriminated when position information is minimal. This result indicates that stereoscopic motion is sensed in a way that cannot be explained by feature tracking or by inferring the motion from memory of position and time.     

Direction-selective coding of stereoscopic (cyclopean) motion

This study employed a selective adaptation paradigm and investigated thresholds for direction discrimination of translational stereoscopic motion (moving binocular disparity information). The stimuli were moving arrays of randomly positioned stereoscopic discs created from disparity embedded in dynamic random-element stereograms. When discrimination thresholds were measured across a range of base directions following adaptation in a fixed direction, discrimination thresholds were maximally elevated 20-30 deg away from adaptation and reduced in the same direction as adaptation. These results are consistent with a distributed-channel model of direction coding and indicate that the direction of stereoscopic motion is encoded by adaptable direction-selective mechanisms similar to those proposed for luminance-defined motion.     

Disparity tuning of the stereoscopic (cyclopean) motion aftereffect

Across five experiments this study investigated the disparity tuning of the stereoscopic motion aftereffect (adaptation from moving retinal disparity). Adapting and test stimuli were moving and stationary stereoscopic grating patterns, respectively, created from dynamic random-dot stereograms. Observers adapted to moving stereoscopic grating patterns presented with a given disparity and viewed stationary test patterns presented with the same or differing disparity to examine whether the motion aftereffect is disparity contingent. Across experiments aftereffect duration was greatest when adapting motion and test pattern both were presented with zero disparity and in the plane of fixation. Aftereffect declined as disparity of adapting motion and/or test pattern increased away from fixation, even under conditions in which depth position of adapt and test was equal. This argues against a relative depth separation explanation of the decline, and instead suggests that the amount of adaptable substrate decreases away from fixation.     

The target in the celestial (moon) illusion.

The visual conditions sufficient to produce the celestial (moon) illusion do not produce it for all presumably suitable celestial targets. For most observers, the illusion is complete for the moon: Apparent visual angle and apparent physical size are inverse functions of elevation, but apparent distance is a direct function. These features of the illusion are attenuated for star clusters and absent for star pairs. Although, in accordance with modern theories of the illusion, the visual terrain may be necessary for the celestial illusion, it is not sufficient; the visual target itself apparently must display particular features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hallucinantion and illusion (author''s transl)

The value of an anaesthetic attachment during the first two postgraduate years is considered under three major headings, the value to the recent graduate, the value to the specialty, and the value to the community. The anaesthetic attachment offers all recent graduates an opportunity to perfect practical skills which should from part of the armamentarium of all doctors, and for some there is the option to acquire the ability to administer a safe anaesthetic. Exposure to the specialty at this time is important for recruitment to the specialist ranks.     

The tactile continuity illusion.

We can perceive the continuity of an object or event by integrating spatially/temporally discrete sensory inputs. The mechanism underlying this perception of continuity has intrigued many researchers and has been well documented in both the visual and auditory modalities. The present study shows for the first time to our knowledge that an illusion of continuity also occurs with vibrotactile stimulation. We found that when the brief temporal gaps inserted into a vibrotactile target were filled with vibrotactile noise, the target vibration was perceived to continue through the noise if the target vibration was sufficiently weak relative to the noise. It is important that the illusory continuity of the vibration cannot be distinguished from the physically continuous vibration. These results therefore suggest that the continuity illusion is common to multiple sensory modalities and that it reflects a fundamental principle of perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The illusion of external agency.

People typically underestimate their capacity to generate satisfaction with future outcomes. When people experience such self-generated satisfaction, they may mistakenly conclude that it was caused by an influential, insightful, and benevolent external agent. In three laboratory experiments, participants who were allowed to generate satisfaction with their outcomes were especially likely to conclude that an external agent had subliminally influenced their choice of partners (Study 1), had insight into their musical preferences (Study 2), and had benevolent intentions when giving them a stuffed animal (Study 3). These results suggest that belief in omniscient, omnipotent, and benevolent external agents, such as God, may derive in part from people's failure to recognize that they have generated their own satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The interaction between stereoscopic and luminance motion

An interaction in apparent motion between perceived three-dimensional forms defined by stereopsis and local luminous elements is reported. Vertical stripes of cyclopean square gratings were simulated by random-dot stereograms. Alternation of two-frame stereograms whose phases differed by 90 deg caused two kinds of percepts, planes' motion in depth (first-order stereoscopic motion, first-order SM) or lateral motion of gratings (higher-order stereoscopic motion, higher-order SM). Experiment 1 explored the conditions under which higher-order SM frequently arose, as opposed to local luminance-based in-depth motion (first-order SM). The results show that, when the spatial arrangements of two-frame random dots were correlated, higher-order SM dominated for long ISI conditions (ISI > 73 msec). When they were uncorrelated, higher-order SM dominated even under zero ISI conditions. Subjects reported that, when higher-order SM was seen, dots were attached to the surfaces of the moving cyclopean figure (motion capture). Experiment 2 tested which factor caused the domination of higher-order SM under uncorrelated conditions in Experiment 1, the larger distance of dot jump or the varied directions of the dots' motion. The results show that, when the distance of dot jump is large or when the directions of dots' motion are incoherent, higher-order SM arises more frequently. When local first-order motion signals are weakened by appropriate temporal and spatial conditions or by incoherent motion directions, higher-order SM dominates and it captures the motion of dots.     

The spindle pole body of yeast

Microtubule organizing centers play an essential cellular role in nucleating microtubule assembly and establishing the microtubule array. The microtubule organizing center of yeast, the spindle pole body (SPB), shares many functions and properties with those other organisms. In recent years considerable new information has been generated concerning components associated with the SPB, and the mechanism by which it duplicates. This article reviews our current view of the cytology and molecular composition of the SPB of the budding yeast, Saccharomyces cerevisiae, and the fission yeast, Schizosaccharomyces pombe. Genetic studies in these organisms has revealed information about how the SPB duplicates and separates, and its roles during vegetative growth, mating and meiosis.     

Contribution toward determining the inner equilibrium of the spinal column (pivotal point as temporary pole) (author's transl)

The estimation of the centre of rotation of a spine segment can be shown as a transient pole, which follows the polar curve of the movement of the upper segment of the spine, relative to the lower one. With the help of X-ray, it is possible to evaluate two separate positions of the pole, from the normal position to the medium flexion and from the medium to the extreme flexion of the lumbal segment. Based on these expected values, as well as their intervals, pathological cases can be recognized, which is also shown in an example.     

The motion analogue of the Café Wall illusion

Detecting visual motion is computationally equivalent to detecting spatiotemporally oriented contours. The question addressed in this study is whether the illusory oriented contour in the space-space domain induces corresponding illusory motion perception. Two experiments were conducted. In experiment 1, the Café Wall pattern, which elicits a strong illusion of orientation (Café Wall illusion), was found to induce an illusion of motion when this pattern was converted to the space-time domain. The strength of the motion illusion depends on the mortar luminance and width, as for the Café Wall illusion. In experiment 2, the adaptation to this illusion of motion was found to induce a motion aftereffect in a static test, which indicates that a first-order-motion system contributes to the induction of the motion illusion. In fact, the motion-energy model was able to predict the strength of this motion aftereffect.     

Object constancy: The illusion of being seen.

Recent theoretical advances in the concept of object constancy have placed it in the context of the child's establishing a separate identity. Although these advances were partly the result of examining the child's growing abilities to evoke a mental image of the absent mother, constancy cannot be well understood as a type of mental representation. It more resembles an illusion, specifically the illusion that the mother is constantly available in her mirroring function. The child's sense of his or her own reality is born in the mother's affectively attuned mirroring, as nothing about the child is real for the child until first seen by the mother. The illusion of the constant object allows the child to construct a sense of his or her own separate reality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The stereoscopic anisotropy: Individual differences and underlying mechanisms.

Observers are more sensitive to variations in the depth of stereoscopic surfaces in a vertical than in a horizontal direction; however, there are large individual differences in this anisotropy. The authors measured discrimination thresholds for surfaces slanted about a vertical axis or inclined about a horizontal axis for 50 observers. Orientation and spatial frequency discrimination thresholds were also measured. For most observers, thresholds were lower for inclination than for slant and lower for orientation than for spatial frequency. There was a positive correlation between the 2 anisotropies, resulting from positive correlations between (a) orientation and inclination thresholds and (b) spatial frequency and slant thresholds. These results support the notion that surface inclination and slant perception is in part limited by the sensitivity of orientation and spatial frequency mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of pictorial illusion on prehension and perception

The present study examined the effect of a size-contrast illusion (Ebbinghaus or Titchener Circles Illusion) on visual perception and the visual control of grasping movements. Seventeen right-handed participants picked up and, on other trials, estimated the size of "poker-chip" disks, which functioned as the target circles in a three-dimensional version of the illusion. In the estimation condition, subjects indicated how big they thought the target was by separating their thumb and forefinger to match the target's size. After initial viewing, no visual feedback from the hand or the target was available. Scaling of grip aperture was found to be strongly correlated with the physical size of the disks, while manual estimations of disk size were biased in the direction of the illusion. Evidently, grip aperture is calibrated to the true size of an object, even when perception of object size is distorted by a pictorial illusion, a result that is consistent with recent suggestions that visually guided prehension and visual perception are mediated by separate visual pathways.     

The neural generation of a unified illusion in human vision

The neural mechanisms of visual binding in humans were investigated by measuring the brain's high-frequency electric responses (36-44 Hz) to the subjective visual perception of a unified three-dimensional illusion. 40 Hz synchronization was found over occipital and right parieto-temporal areas 500-300 ms before visual awareness of the three-dimensional Gestalt was reported, but not during the viewing of the illusion. At lower frequency bands (8-13 Hz and 13-20 Hz) no corresponding synchronization was found. 40 Hz synchronization thus directly correlates with the construction and emergence of a unified visual percept and may reflect the rapid formation of transient functional connections between spatially separated cortical areas.     

Comparison of grouping abilities in humans (Homo sapiens) and baboons (Papio papio) with the Ebbinghaus illusion.

This research comparatively assessed grouping mechanisms of humans (n = 8) and baboons (n = 8) in an illusory task that employs configurations of target and surrounding circles arranged to induce the Ebbinghaus (Titchener) illusion. Analyses of response behaviors and points of subjective equality demonstrated that only humans misjudged the central target size under the influence of the Ebbinghaus illusion, whereas baboons expressed a more veridical perception of target sizes. It is argued that humans adopted a global mode of stimulus processing of the illusory figure in our task that has favored the illusion. By contrast, a strong local mode of stimulus processing with attention restricted to the target must have prevented illusory effects in baboons. These findings suggest that monkeys and humans have evolved modes of object recognition that do not similarly rely on the same gestalt principles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The line–motion illusion: Attention or impletion?

When a brief lateral cue precedes an instantaneously presented horizontal line, observers report a sensation of motion in the line propagating from the cued end toward the uncued end. This illusion has been described as a measure of the facilitatory effects of a visual attention gradient (O. Hikosaka, S. Miyauchi, & S. Shimojo, 1993a). Evidence in the present study favors, instead, an account in which the illusion is the result of an impletion process that fills in interpolated events after the cue and the line are linked as successive states of a single object in apparent motion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)