Abstract: When a tone-burst train with a short inter-burst interval is lateralized to the left and is followed by another tone-burst train lateralized to the right, listeners report a smooth shift of tone bursts along the intracranial axis from left to right (known as auditory saltation). When a sequence of tone bursts with a changing interaural time difference is presented, listeners also report a smooth shift of tone bursts (simulated auditory motion). In this study, an investigation was carried out to determine whether the movement of sound sources, such as auditory saltation and simulated auditory motion, are influenced by changes in frequency between or across tone bursts. The results show that abrupt changes in frequency hamper the perceived smoothness of auditory saltation and simulated auditory motion. In contrast, gradual changes in frequency retain the smoothness of auditory saltation and simulated auditory motion. These results indicate that perceptual grouping based on frequency of tone bursts influences the smoothness of the movement of sound sources.
Abstract: BACKGROUND: Perceived spatial intervals between successive flashes can be distorted by varying the temporal intervals between them (the "tau effect"). A previous study showed that a tau effect for visual flashes could be induced when they were accompanied by auditory beeps with varied temporal intervals (an audiovisual tau effect). METHODOLOGY/PRINCIPAL FINDINGS: We conducted two experiments to investigate whether the audiovisual tau effect occurs in infancy. Forty-eight infants aged 5-8 months took part in this study. In Experiment 1, infants were familiarized with audiovisual stimuli consisting of three pairs of two flashes and three beeps. The onsets of the first and third pairs of flashes were respectively matched to those of the first and third beeps. The onset of the second pair of flashes was separated from that of the second beep by 150 ms. Following the familiarization phase, infants were exposed to a test stimulus composed of two vertical arrays of three static flashes with different spatial intervals. We hypothesized that if the audiovisual tau effect occurred in infancy then infants would preferentially look at the flash array with spatial intervals that would be expected to be different from the perceived spatial intervals between flashes they were exposed to in the familiarization phase. The results of Experiment 1 supported this hypothesis. In Experiment 2, the first and third beeps were removed from the familiarization stimuli, resulting in the disappearance of the audiovisual tau effect. This indicates that the modulation of temporal intervals among flashes by beeps was essential for the audiovisual tau effect to occur (Experiment 2). CONCLUSIONS/SIGNIFICANCE: These results suggest that the cross-modal processing that underlies the audiovisual tau effect occurs even in early infancy. In particular, the results indicate that audiovisual modulation of temporal intervals emerges by 5-8 months of age.
Abstract: The purpose of the present study was two-fold. First we examined whether visible motion appearance was altered by the spatial interaction between invisible and visible motion. We addressed this issue by means of simultaneous motion contrast, in which a horizontal test grating with a counterphase luminance modulation was seen to have the opposite motion direction to a peripheral inducer grating with unidirectional upward or downward motion. Using a mirror stereoscope, observers viewed the inducer and test gratings with one eye, and continuous flashes of colorful squares forming an annulus shape with the other eye. The continuous flashes rendered the inducer subjectively invisible. The observers' task was to report whether the test grating moved upward or downward. Consequently, simultaneous motion contrast was observed even when the inducer was invisible (Experiment 1). Second, we examined whether the observers could correctly respond to the direction of invisible motion: It was impossible (Experiment 2).
Abstract: In this study, I examined how sequential stream segregation contributes to the detection of diotic tones among tones with time-varying interaural time differences (ITDs). Target (T) and distractor (D) tones, and a silent duration (-) formed a sequence (DTD -) and this sequence was presented repeatedly. A frequency difference was introduced between target and distractor tones. The distractor tones were also given time-varying ITDs to produce a percept of smooth auditory motion along the interaural axis. In half of the trials, the target tones were not given time-varying ITDs, and thus were diotically presented. The task of the listeners was to determine whether the repeated sequences of DTD - had target tones without motion. The sensitivity d' for the detection of diotic target tones was higher with larger frequency differences. On the other hand, the criterion c was lower with larger frequency differences. In another session, I confirmed that proportions of reports "two streams" was positively and negatively correlated with d' and c, respectively. The results indicate that the localisation of a sound image could be influenced by sequential stream segregation in complex sound environments.
Abstract: The scintillating grid illusion refers to the illusory perception of black spots on luminance patches at the intersections of a grey grid on a black background. We examined how spatial parameters of luminance patches modulated the strength of the illusion. In experiment 1, we controlled the size and shape of the luminance patches. For the largest-size conditions tested, we found a significant reduction in the strength of the illusion with squares when compared to circles or diamonds. In experiment 2, we controlled the orientation of quadrangle patches and confirmed a significantly larger reduction in the strength of the illusion when the edge orientations of quadrangle patches were vertical and horizontal (square) than when they were oblique (diamond). To explore the relationship between orientation processing and scintillating grid illusion, we controlled, in experiment 3, the global orientation of the display; the strength of the illusion with diamonds was significantly weaker when it was rotated by 45 degrees than when it was not rotated. These results indicate that it is not only the difference of edge orientation of luminance patches, but also the orientation with respect to the grid that determines the strength of the illusion.
Abstract: When sequential visual flashes are accompanied by a lower number of sequential auditory pulses, the perceived number of visual flashes is lower than the actual number, an illusion termed 'flash fusion'. We examined whether temporal capture of flashes by pulses underlay flash fusion. One of the visual flashes was given a luminance increment, and observers reported which flash had the luminance increment. Results showed that the pulse strongly captured the flashes in its temporal vicinity, resulting in flash fusion. Moreover, when one of the successive pulses was given a higher frequency than others, the luminance increment was perceptually paired with the pulse with the higher frequency. The pairing of audiovisual features disappeared when the temporal pattern of the pulse frequency was difficult for the observer to anticipate. These data indicate that flash fusion is caused by temporal capture of flashes by the pulse, and that feature matching between auditory and visual signals also contributes to the modulation of perceived temporal structure of flashes during flash fusion.
Abstract: This study examined the effects of odors on sustained attention during a vigilance task. Two essential oils (lavender and eucalyptus) and two materials (l-menthol and linalyl acetate) were compared with a control. The increase in reaction time was significantly lower with lavender than with the control. The results suggest that the administration of lavender helped to maintain sustained attention during the long-term task.
Abstract: Motion lines (MLs) are a pictorial technique used to represent object movement in a still picture. This study explored how MLs contribute to motion perception. In Experiment 1, we reported the creation of a motion illusion caused by MLs: random displacements of objects with MLs on each frame were perceived as unidirectional global motion along the pictorial motion direction implied by MLs. In Experiment 2, we showed that the illusory global motion in the peripheral visual field captured the perceived motion direction of random displacement of objects without MLs in the central visual field, and confirmed that the results in Experiment 1 did not stem simply from response bias, but resulted from perceptual processing. In Experiment 3, we showed that the spatial arrangement of orientation information rather than ML length is important for the illusory global motion. Our results indicate that the ML effect is based on perceptual processing rather than response bias, and that comparison of neighboring orientation components may underlie the determination of pictorial motion direction with MLs.
Abstract: This study examined the role of spatiotemporal feature attribution in the perception of the visual size of objects. A small or a large leading disk, a test disk of variable size, and a probe disk of a fixed size were sequentially presented at the same position for durations of 16.7 ms with interstimulus intervals of 117 ms. Observers compared the visual size of the test with the probe disk. The size of the test disk was underestimated and overestimated when the test followed small and large leading disks, respectively (Experiment 1). These modulations of visual size occurred even when disks were sequentially presented so as to invoke apparent motion (Experiment 2). Furthermore, when two streams of apparent motion consisting of the three types of disk were diagonally overlapped, modulation of visual size occurred in accordance with the size of the attended leading disk (Experiment 3). Retinotopic and non-retinotopic feature attribution and the related attentional mechanisms are discussed.
Abstract: This study examined whether a briefly presented target was mislocalized toward a subjective contour. Observers manually reproduced the position of a briefly presented peripheral target circle above a central fixation cross. A luminance contour, a subjective contour, or a no-contour stimulus was presented in either the left of right visual field, and a no-contour control was presented in the opposite visual field. After these stimuli vanished, a target circle was then presented. Consequently, the degree of mislocalization toward the subjective and luminance contours was the same; this indicated that image integration at a coarse spatial scale cannot explain mislocalization. Experiment 2 revealed that the mislocalization in Experiment 1 was not a result of eye movements. Experiment 3 found that the spatial attention allocated at the location of the luminance and subjective contours was more than that allocated at the no-contour stimulus. An attentional shift toward the task-irrelevant stimulus resulted in a mislocalization of the target.
Abstract: This study investigated how spatial intervals between successive visual flashes are influenced by the temporal intervals between auditory pure tones presented concurrently with the flashes. Three successive visual flashes defined two spatial intervals with different extents as well as two equal temporal intervals. The onsets of the first and third tones were temporally aligned with those of the first and third flashes, while the onset of the second tone was temporally offset to that of the second visual flash, resulting in shorter or longer temporal intervals between pairs of tones. Observers judged which of the first or second spatial intervals between flashes was shorter. The results showed that the shorter temporal interval between tones caused underestimation of the spatial interval between flashes. On the other hand, stimuli without the first and third tones did not result in underestimation of spatial intervals between flashes. These results indicate an audiovisual tau effect, which is triggered by a constant velocity assumption applied to moving objects defined by more than one modality.
Abstract: This study examined the subjective disappearance of a visual object induced by a neighboring flickering ring (Experiments 1 and 2), a set of four flickering dots (Experiment 3), and apparent motion (Experiment 4) as flickering flankers. Observers were asked to report whether a target disappeared during 10 s of stimulus presentation. We used the proportion of disappearance as a measure of performance. Interestingly, subjective disappearance was rarely observed when flickering flankers were presented with a separation of less than 0.5 degrees from the target. However, disappearance was observed when dynamic random-dot patterns were presented with a separation of less than 0.5 degrees from the target border (Experiment 5). Our results indicate that the flicker of flankers near the target disturbs target adaptation or attentional inhibition, causing persistent target representation in higher-order object selection, and resulting in non-disappearance of the target.
Abstract: In motion-induced blindness (MIB), a target within rotating random dots is occasionally hidden from observers' consciousness during observation. In the present study, a red ring-like cue was centered on a target and presented immediately after observers reported subjective disappearance of the target in MIB (Experiment 1). The radius of the cue was systematically modulated. Observers quickly regained awareness of the disappeared object only after they were provided with a pinpoint cue of its location. We also found that a flickering cue at 1Hz hindered MIB when the radius of the cue was critically small (Experiment 2). Furthermore, abrupt onset of a small square was enough to regain awareness of the target (Experiment 3). Successful revival of the target with a small cue indicates that critical spatial distribution of visual attention determines what in the visual scene is included in visual awareness.
Abstract: Artists and cartoonists are able to dexterously depict a running person on paper with the aid of 'motion lines'. We scientifically examined whether the cognitive system can exploit motion lines in constructing memory representations of the location of a running person depicted in a still image. A target depicting a standing or a running person with or without motion lines was presented to participants for 500 ms. Observers were required to reproduce the location of the target 1 s after its disappearance. Data from depicted leftward and rightward moving persons were collapsed. Memory displacement of the target was shown to be largest in the presence of motion lines and a posture indicating an identical direction of movement. By assessing the absolute localization error, we showed that there was no localization advantage toward a target with a symmetrical (standing) posture over one with an asymmetrical (running) posture. Our findings indicate synergetic interaction between the mechanisms responsible for processing of motion lines and human postures in the representation of dynamic events.
Abstract: In this study, we examined the contribution of the orientation of moving objects to perception of a streaming/bouncing motion display. In three experiments, participants reported which of the two types of motion, streaming or bouncing, they perceived. The following independent variables were used: orientation differences between Gabor micropatterns (Gabors) and their path of motion (all the experiments) and the presence/absence of a transient tone (Experiment 1), transient visual flash (Experiment 2), or concurrent secondary task (Experiment 3) at the coincidence of Gabors. The results showed that the events at coincidence generally biased responses toward the perception of bouncing. On the other hand, alignment of Gabors with their motion axes significantly reduced the frequency of bounce perception. The results also indicated that an object whose orientation was parallel to its motion path strengthened the spatiotemporal integration of local motion signals along a straight motion path, resulting in the perception of streaming. We suggest that the effect of collinearity between Gabors and their motion path is relatively free from the effect of attention distraction.
Abstract: This study investigated how visual systems recover depth-order from orientation-defined junctions. Stimuli were superimposed stripes defined by Gabor micro-patterns (Gabors). In one stripe (random stripe), Gabor orientation was randomly selected from a given range, while in the other (constant stripe) it was selected so as to be different from the mean orientation of the random stripe by 90 degrees . Observers reported which of the two stripes, the right- or left-tilted one, they perceived as "nearer" than the other. Observers frequently reported that the random stripe was nearer than the constant stripe. The results appeared to stem from detection of discontinuity of texture edges of the constant stripe due to masking by the random stripe at junctions. This idea was confirmed in the following experiments where discontinuity of the texture edges at junctions was introduced by changing the Gabor luminance contrast in one stripe but keeping it intact in the other. The results indicated that processing of texture edges at junctions can contribute to the perception of depth-order.
Abstract: This study examined the involvement of second-order processing in the perception of transparency from texture. Stimuli consisted of two superimposed plaid patterns with two diagonal gratings defined by contrast modulation. We investigated the probability of reporting transparency (simultaneous percept of the two gratings) as functions of envelope frequency and either carrier frequency (Experiment 1) or carrier orientation (Experiment 2). Perception of transparency was more often with a large difference in carrier signals between the two gratings. Moreover, a lower envelope frequency was required for the perception of transparency. These results indicate that the mechanism responsible for texture transparency may tune to second-order structures that are differentiated in terms of first-order signals and that decomposition or integration of structures may be determined in terms of the difference of first-order signals between structures.
Abstract: We investigated the effects of spatial and temporal factors on manual localization of a visual target by measuring accuracy, precision, and bias. Spatial factors included manipulation of display as with or without distracters, with invariant or variant distracters, and with near or far distracters, respectively, in Experiments 1, 2, and 3. The target and distracters were of 1degrees dots differing only by luminance parameter; they were presented concurrently for 150 or 1000 ms while observers had to memorize the target location maintaining a fixed gaze. The observers' task was to reproduce the location of the target with a mouse cursor available 150 ms following stimuli offset. Results from all experiments showed that localization performance for a briefly exposed target was as accurate and precise as that for a long exposed target. Moreover, manipulation of spatial factors had no systematic effects on accuracy and precision except that near distracters yielded higher precision. Interestingly, localization performance was unbiased in 150 ms condition when there were distracters in the display, while being biased towards the fovea in 1000 ms condition regardless of their presence or absence. These results suggest a temporal dynamics in dominance-suppression between egocentric and exocentric cues in the construction of memory for location.
Abstract: Two experiments examined which of two mechanisms, attention shift or memory averaging, reduces foveal bias. The target stimulus was a black dot presented for 80 ms while observers maintained fixation. The two main conditions were 'with' and 'without' vertical and horizontal bars as landmarks, which were placed on more eccentric positions than the target stimulus. To induce attention, the landmark was flashed on for 80 ms (Experiment 1) or disappeared (Experiment 2) with a stimulus onset asynchrony of 0, 106.4, or 212.8 ms in both experiments. As a control, non-flashed and non-disappeared landmark conditions were employed. The observers' task was to point to the remembered location of the target with a mouse cursor. The results showed that the magnitudes of foveal bias were significantly lower in the flashed and disappeared landmark conditions than in the without landmark condition. Furthermore, the magnitudes in the flashed and disappeared landmark conditions did not differ from their respective control conditions. The latter finding in the disappeared landmark conditions provides evidence for 'attention shift' against 'memory averaging' as the mechanism reducing foveal bias.
Abstract: This study was designed to ascertain whether the human visual system can segregate overlapped surfaces by integrating texture borders at second-order X-junctions. The stimuli used were crossed vertical and horizontal stripes consisting of Gabor micro-patterns. We manipulated the orientation of the center region of each stripe. Observers judged whether the crossed stripes appeared as "two overlapped stripes" or "five individual regions." The results showed that the probability of perceiving overlapped stripes exceeded the chance level (0.5) when the orientation differences between the center and flanking regions were less than 30 degrees. We suggest that the integration of texture borders along each stripe occurs by the filter-rectify-filter mechanism, resulting in the impression of overlapped surfaces. When this fails, the outcome is the perception of five individual regions.
Abstract: This study examined the factors producing the perception of transparency between overlaid regions composed of Gabor micro-patterns as functions of their spatial frequency, separation of overlaid regions, and types of orientation modulation. The results showed that the likelihood of perceiving transparency was high both when (1) the difference in Gabor spatial frequency between regions was large, and (2) the region boundary, which was formed by short-range orientation differences in the Gabor micro-patterns, clearly emerged. We conclude that texture transparency appears to result from an interaction between a boundary-detection mechanism defining the shape of each region and a surface-detection mechanism assigning the boundary.
Abstract: We report on the reversal of asymmetry in visual-search tasks with shaded items. Previous studies have suggested that the target of a bottom-lit disk among distractors of top-lit disks is detected in a rapid and parallel manner, but not vice versa. However, in this study, we have shown that the compound items of top-lit disks were searched more quickly than those composed of bottom-lit disks where the items had to be segregated from their background. By modulating the inter-element distances, we confirmed that the reversal of search asymmetry cannot be due to the grouping of items. Further, we showed that the regions of the top-lit disks were perceived as figure more consistently than those of bottom-lit disks. The results indicate that the boundary assignment to the compound items of the top-lit disks enhances the segregation of search items from the background, and that the search mechanism may access the relatively higher representation that includes figure-ground relations.
