Akihiro Yagi - Academia.edu (original) (raw)

Papers by Akihiro Yagi

Research paper thumbnail of The Implicit Processing in Multiple Object Tracking

Previous research has shown that implicit memory of visual context guides visual attention to a t... more Previous research has shown that implicit memory of visual context guides visual attention to a target object in a dynamic scene . We investigated how attention affects implicit learning of contextual information in dynamic scene using a multiple object tracking (MOT) task. Participants were asked to track five identical targets which moved independently and unpredictably among five identical distractors. In this task, the motion patterns (trajectories) of the target items (Experiment 1) or the distractor items (Experiment 2) were made invariant by repeating them throughout the entire experimental session. The results showed that the invariant motion patterns of the target set improved MOT performance implicitly. In addition, participants demonstrated greater performance when the motion patterns of both target and distractor set were made invariant. This additional facilitation by the distractor set was not observed when only patterns of the distractor set was repeated. These data suggest contextual modulation of attentional tracking and sensitivity to the global motion pattern in a dynamic scene.

Research paper thumbnail of Motion Illusion in Video Images of Human Movement

Lecture Notes in Computer Science, 2005

We found a novel motion illusion; when a video clip presents a moving person, the background imag... more We found a novel motion illusion; when a video clip presents a moving person, the background image appears to move incorrectly. We investigated this illusion with psychophysical experiments using a movie display that consisted of a human figure and a vertical grating pattern. The grating periodically reversed its light-dark phase so that it was ambiguous in terms of motion directions. However, when the human figure presented a walking gait in front of the grating, the grating appears to move in the opposite direction of her/his locomotion. This illusion suggests that human movements modulate perception of video images, and that creators of entertainment images need to pay attention to background images in videos used in animation and computer graphics.

Research paper thumbnail of A temporal window for estimating surface brightness in the Craik-O'Brien-Cornsweet effect

Frontiers in Human Neuroscience, 2014

The central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions wi... more The central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions with identical luminance appear to be different. This brightness illusion, called the Craik-O'Brien-Cornsweet effect (COCe), can be explained by low-level spatial filtering mechanisms (Dakin and Bex, 2003). Also, the COCe is greatly reduced when the stimulus lacks a frame element surrounding the COC edge (Purves et al., 1999). This indicates that the COCe can be modulated by extra contextual cues that are related to ideas about lighting priors. In this study, we examined whether processing for contextual modulation could be independent of the main COCe processing mediated by the filtering mechanism. We displayed the COC edge and frame element at physically different times. Then, while varying the onset asynchrony between them and changing the luminance contrast of the frame element, we measured the size of the COCe. We found that the COCe was observed in the temporal range of around 600-800 ms centered at the 0 ms (from around -400 to 400 ms in stimulus onset asynchrony), which was much larger than the range of typical visual persistency. More importantly, this temporal range did not change significantly regardless of differences in the luminance contrast of the frame element (5-100%), in the durations of COC edge and/or the frame element (50 or 200 ms), in the display condition (interocular or binocular), and in the type of lines constituting the frame element (solid or illusory lines). Results suggest that the visual system can bind the COC edge and frame element with a temporal window of ~1 s to estimate surface brightness. Information from the basic filtering mechanism and information of contextual cue are separately processed and are linked afterwards.

Research paper thumbnail of Improvement of chromatic temporal resolution during smooth pursuit eye movement

Journal of Vision - J VISION, 2010

Research paper thumbnail of Larger forward memory displacement in the direction of gravity

Research paper thumbnail of Contextual cueing in multiple object tracking

Visual Cognition, 2009

ABSTRACT In this study, we examined whether visual context can be learned through a dynamic displ... more ABSTRACT In this study, we examined whether visual context can be learned through a dynamic display and whether it can facilitate sustained attentional tracking by combining a multiple object tracking (MOT) task and a contextual cueing procedure. The trajectories of the targets and distractors in the MOT task were made invariant by repeatedly presenting them. The results revealed that when the targets were repeatedly displayed, tracking performance implicitly improved, and this effect was enhanced when the unattended distractors in the displays were also repeated. However, the repetition of the distractors alone did not produce any effect. Interestingly, when the targets and distractors were switched in a display in which the distractors had been previously repeated, the tracking performance was impaired as compared with that in the case of nonrepeated displays. We concluded that the contextual information in a dynamic display facilitates attentional tracking and that different types of contextual modulations occurred in MOT processes, such as facilitation for attended targets and inhibition for ignored distractors.

Research paper thumbnail of Perception of motion trajectory of object from the moving cast shadow in infants

Vision Research, 2006

A moving cast shadow of the object affects the perception of the objectÕs trajectory in adults [K... more A moving cast shadow of the object affects the perception of the objectÕs trajectory in adults [Kersten, D.

Research paper thumbnail of Infants’ sensitivity to shading and line junctions

Vision Research, 2008

We examined the sensitivity to shading and line junction cues in human infants aged 5-8 months us... more We examined the sensitivity to shading and line junction cues in human infants aged 5-8 months using computer-generated displays containing a rectangular-wave grating and a serrated aperture. In Experiment 1, infants were presented with a pair of displays: a two-dimensional to three-dimensional (2D-3D) display, alternating between 2D and 3D images, and a 2D-2D display, alternating between two 2D images. The 3D image consisted of black-and-white borders aligned with the peaks of a serrated aperture, creating the appearance of a 3D folded surface. The 2D image consisted of the black-and-white borders misaligned with the peaks of a serrated aperture, which does not create a 3D impression for adults. Seven-and 8-month-old infants looked longer at the 2D-3D display than the 2D-2D display. In contrast, 5-and 6-month-old infants did not exhibit a looking preference. In Experiment 2, we used images with double-cycle rectangular-wave gratings to impair shading information. These images consisted of blackand-white borders aligned with half of the peaks and misaligned with latter half of the peaks of a serrated aperture, giving the appearance of surface markings. Seven-and 8-month-old infants did not exhibit a significant difference in preference between the two test displays. These results could not be explained by the young infant's failure of discrimination due to the experimental procedure (Experiment 3). These results showed that the sensitivity to shading and line junctions change between 5-6 and 7-8 months of age.

Research paper thumbnail of Strength and variability of the backscroll illusion

Vision Research, 2009

When a walking person is presented in a movie, the background image appears to move in a directio... more When a walking person is presented in a movie, the background image appears to move in a direction opposite to that of the person's locomotion. This study aimed to quantify the strength of this backscroll illusion and to examine interobserver and intraobserver variability. Stimuli were movie clips that presented a walking person in profile against a background of dynamic grating composed of two vertical sinusoidal gratings moving in opposite directions. Employing a motion-nulling method, we controlled the ratio of luminance contrasts of the component gratings to determine points that canceled the percept of unidirectional motion in the grating background. Results across 50 observers showed that the backscroll illusion disappeared when a luminance contrast of moving grating components consistent with a walker's direction was about twice as high as that for the opposite motion direction. Intraobserver variability was relatively small. However, nulling points for individual observers were more variable under conditions with dynamically moving walkers than conditions presenting only a static picture of a walker. We speculated on the underlying mechanisms of the backscroll illusion in relation to similar phenomena.

Research paper thumbnail of A continuously lit stimulus is perceived to be shorter than a flickering stimulus during a saccade

Spatial Vision, 2005

When subjects made a saccade across a single-flashed dot, a flickering dot or a continuous dot, t... more When subjects made a saccade across a single-flashed dot, a flickering dot or a continuous dot, they perceived a dot, an array (phantom array), or a line (phantom line), respectively. We asked subjects to localize both endpoints of the phantom array or line and calculated the perceived lengths. Based on the findings of Matsumiya and Uchikawa , we predicted that the apparent length of the phantom line would be larger than that of the phantom array. In Experiment 1 of the current study, contrary to the prediction, the phantom line was found to be shorter than the phantom array. In Experiment 2, we investigated whether the function underlying the filled-unfilled space illusion (Lewis, 1912) instead of the function underlying the saccadic compression could explain the results. Subjects were asked to localize both endpoints of a line or an array while keeping their eyes fixated. Although the results of Experiment 2 showed that the perceived length of a line was shorter than that of an array, the function underlying the filled-unfilled illusion could not fully account for the results of Experiment 1. To explain the present results, we proposed a model for the localization process and discussed its validity.

Research paper thumbnail of Inhibitory Tagging on Randomly Moving Objects

Psychological Science, 2002

Inhibitory tagging is a process that prevents focal attention from revisiting previously checked ... more Inhibitory tagging is a process that prevents focal attention from revisiting previously checked items in inefficient searches, facilitating search performance. Recent studies suggested that inhibitory tagging is object rather than location based, but it was unclear whether inhibitory tagging operates on moving objects. The present study investigated the tagging effect on moving objects. Participants were asked to search for a moving target among randomly and independently moving distractors. After either efficient or inefficient search, participants performed a probe detection task that measured the inhibitory effect on search items. The inhibitory effect on distractors was observed only after inefficient searches. The present results support the concept of object-based inhibitory tagging.

Research paper thumbnail of MISMATCH NEGATIVITY RELATED TO UPDATING INFORMATION IN OBJECT FILES

PSYCHOLOGIA -An International Journal of Psychology in the Orient, 2005

Research paper thumbnail of Smooth Pursuit Eye Movements Improve Temporal Resolution for Color Perception

PLoS ONE, 2010

Human observers see a single mixed color (yellow) when different colors (red and green) rapidly a... more Human observers see a single mixed color (yellow) when different colors (red and green) rapidly alternate. Accumulating evidence suggests that the critical temporal frequency beyond which chromatic fusion occurs does not simply reflect the temporal limit of peripheral encoding. However, it remains poorly understood how the central processing controls the fusion frequency. Here we show that the fusion frequency can be elevated by extra-retinal signals during smooth pursuit. This eye movement can keep the image of a moving target in the fovea, but it also introduces a backward retinal sweep of the stationary background pattern. We found that the fusion frequency was higher when retinal color changes were generated by pursuit-induced background motions than when the same retinal color changes were generated by object motions during eye fixation. This temporal improvement cannot be ascribed to a general increase in contrast gain of specific neural mechanisms during pursuit, since the improvement was not observed with a pattern flickering without changing position on the retina or with a pattern moving in the direction opposite to the background motion during pursuit. Our findings indicate that chromatic fusion is controlled by a cortical mechanism that suppresses motion blur. A plausible mechanism is that eye-movement signals change spatiotemporal trajectories along which color signals are integrated so as to reduce chromatic integration at the same locations (i.e., along stationary trajectories) on the retina that normally causes retinal blur during fixation.

Research paper thumbnail of Global interference: The effect of exposure duration that is substituted for spatial frequency

Perception, 2002

In this study, participants were required to identify hierarchically structured patterns that app... more In this study, participants were required to identify hierarchically structured patterns that appeared at either global or local level. Paquet and Merikle (1984 Canadian Journal of Psychology 381 45-53) showed that global interference is affected by exposure duration in the processing of a hierarchical structure. They showed that only global-to-local interference occurred at short exposure durations. In contrast, global-to-local as well as local-to-global interference was observed at long exposure durations. They suggested that the effect of exposure duration with global interference depends on the high-spatial-frequency versus low-spatial-frequency channel. In the present study, exposure duration (short or long) was varied randomly from trial to trial (experiment 1), or held constant (experiment 2). In experiment 1, global-to-local interference occurred at both short and long exposure durations, even though the same physical properties existed as in experiment 2. In experiment 2, both global-to-local and local-to-global interference occurred at only long exposure durations, in line with the results reported by Paquet and Merikle. This suggests that the effect of exposure duration on global interference is explained not only by spatial-frequency channels, but also by attentional shift.

Research paper thumbnail of Biological motion alters coherent motion perception

Perception, 2008

When a movie presents a person walking, the background appears to move in the direction opposite ... more When a movie presents a person walking, the background appears to move in the direction opposite to the person's gait. This study verified this backscroll illusion by presenting a point-light walker against a background of a random-dot cinematogram (RDC). The RDC consisted of some signal dots moving coherently either leftward or rightward among other noise dots moving randomly. The method of constant stimuli was used to vary the RDC in motion coherence from trial to trial by manipulating the direction and percentage of the signal dots. Six observers judged the perceived direction of coherent motion in a two-alternative forced-choice procedure. Response rates for coherent motion perception in the direction opposite to walking were evaluated as a function of motion coherence. The results showed that the psychometric function shifted toward the direction determined by a bias in the opposite direction to the walker. The mean threshold was about half as high as that in a control condition in which the positions of the point-lights were scrambled to impair the recognition of the walker. The results demonstrate that biological motion noticeably affects the appearance of motion coherence in the background.

Research paper thumbnail of Reduction of stimulus visibility compresses apparent time intervals

Nature Neuroscience, 2008

The neural mechanisms underlying visual estimation of subsecond durations remain unknown, but per... more The neural mechanisms underlying visual estimation of subsecond durations remain unknown, but perisaccadic underestimation of interflash intervals may provide a clue as to the nature of these mechanisms. Here we found that simply reducing the flash visibility, particularly the visibility of transient signals, induced similar time underestimation by human observers. Our results suggest that weak transient responses fail to trigger the proper detection of temporal asynchrony, leading to increased perception of simultaneity and apparent time compression.

Research paper thumbnail of The pointedness effect on representational momentum

Memory & Cognition, 2001

An observer's memory for the final position of a moving object is shifted forward in the directio... more An observer's memory for the final position of a moving object is shifted forward in the direction of that object's motion. It is called representational momentum (RM). This study addressed stimulusspecific effects on RM. In Experiment 1, participants showed larger memory shift for an object moving in its typical direction of motion than when it moved in a nontypical direction of motion. In Experiment 2, participants indicated larger memory shift for a pointed pattern moving in the direction of its point than when it moved in the opposite direction. In Experiment 3, we again examined the influences of knowledge about objects' typical motions and the pointedness of objects, because we did not control the shape (pointedness) of objects in Experiment 1. The results showed that only pointedness affected the magnitude of memory shift and that the effect was smaller than the momentum effect.

Research paper thumbnail of Perception of motion trajectory from the moving cast shadow in human infants

Research paper thumbnail of Priming effects in multiple object tracking: An implicit encoding based on global spatiotemporal information

Research paper thumbnail of Asymmetry in the detection of shapes from shading in infants 1

Japanese Psychological Research, 2008

ABSTRACT

Research paper thumbnail of The Implicit Processing in Multiple Object Tracking

Previous research has shown that implicit memory of visual context guides visual attention to a t... more Previous research has shown that implicit memory of visual context guides visual attention to a target object in a dynamic scene . We investigated how attention affects implicit learning of contextual information in dynamic scene using a multiple object tracking (MOT) task. Participants were asked to track five identical targets which moved independently and unpredictably among five identical distractors. In this task, the motion patterns (trajectories) of the target items (Experiment 1) or the distractor items (Experiment 2) were made invariant by repeating them throughout the entire experimental session. The results showed that the invariant motion patterns of the target set improved MOT performance implicitly. In addition, participants demonstrated greater performance when the motion patterns of both target and distractor set were made invariant. This additional facilitation by the distractor set was not observed when only patterns of the distractor set was repeated. These data suggest contextual modulation of attentional tracking and sensitivity to the global motion pattern in a dynamic scene.

Research paper thumbnail of Motion Illusion in Video Images of Human Movement

Lecture Notes in Computer Science, 2005

We found a novel motion illusion; when a video clip presents a moving person, the background imag... more We found a novel motion illusion; when a video clip presents a moving person, the background image appears to move incorrectly. We investigated this illusion with psychophysical experiments using a movie display that consisted of a human figure and a vertical grating pattern. The grating periodically reversed its light-dark phase so that it was ambiguous in terms of motion directions. However, when the human figure presented a walking gait in front of the grating, the grating appears to move in the opposite direction of her/his locomotion. This illusion suggests that human movements modulate perception of video images, and that creators of entertainment images need to pay attention to background images in videos used in animation and computer graphics.

Research paper thumbnail of A temporal window for estimating surface brightness in the Craik-O'Brien-Cornsweet effect

Frontiers in Human Neuroscience, 2014

The central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions wi... more The central edge of an opposing pair of luminance gradients (COC edge) makes adjoining regions with identical luminance appear to be different. This brightness illusion, called the Craik-O'Brien-Cornsweet effect (COCe), can be explained by low-level spatial filtering mechanisms (Dakin and Bex, 2003). Also, the COCe is greatly reduced when the stimulus lacks a frame element surrounding the COC edge (Purves et al., 1999). This indicates that the COCe can be modulated by extra contextual cues that are related to ideas about lighting priors. In this study, we examined whether processing for contextual modulation could be independent of the main COCe processing mediated by the filtering mechanism. We displayed the COC edge and frame element at physically different times. Then, while varying the onset asynchrony between them and changing the luminance contrast of the frame element, we measured the size of the COCe. We found that the COCe was observed in the temporal range of around 600-800 ms centered at the 0 ms (from around -400 to 400 ms in stimulus onset asynchrony), which was much larger than the range of typical visual persistency. More importantly, this temporal range did not change significantly regardless of differences in the luminance contrast of the frame element (5-100%), in the durations of COC edge and/or the frame element (50 or 200 ms), in the display condition (interocular or binocular), and in the type of lines constituting the frame element (solid or illusory lines). Results suggest that the visual system can bind the COC edge and frame element with a temporal window of ~1 s to estimate surface brightness. Information from the basic filtering mechanism and information of contextual cue are separately processed and are linked afterwards.

Research paper thumbnail of Improvement of chromatic temporal resolution during smooth pursuit eye movement

Journal of Vision - J VISION, 2010

Research paper thumbnail of Larger forward memory displacement in the direction of gravity

Research paper thumbnail of Contextual cueing in multiple object tracking

Visual Cognition, 2009

ABSTRACT In this study, we examined whether visual context can be learned through a dynamic displ... more ABSTRACT In this study, we examined whether visual context can be learned through a dynamic display and whether it can facilitate sustained attentional tracking by combining a multiple object tracking (MOT) task and a contextual cueing procedure. The trajectories of the targets and distractors in the MOT task were made invariant by repeatedly presenting them. The results revealed that when the targets were repeatedly displayed, tracking performance implicitly improved, and this effect was enhanced when the unattended distractors in the displays were also repeated. However, the repetition of the distractors alone did not produce any effect. Interestingly, when the targets and distractors were switched in a display in which the distractors had been previously repeated, the tracking performance was impaired as compared with that in the case of nonrepeated displays. We concluded that the contextual information in a dynamic display facilitates attentional tracking and that different types of contextual modulations occurred in MOT processes, such as facilitation for attended targets and inhibition for ignored distractors.

Research paper thumbnail of Perception of motion trajectory of object from the moving cast shadow in infants

Vision Research, 2006

A moving cast shadow of the object affects the perception of the objectÕs trajectory in adults [K... more A moving cast shadow of the object affects the perception of the objectÕs trajectory in adults [Kersten, D.

Research paper thumbnail of Infants’ sensitivity to shading and line junctions

Vision Research, 2008

We examined the sensitivity to shading and line junction cues in human infants aged 5-8 months us... more We examined the sensitivity to shading and line junction cues in human infants aged 5-8 months using computer-generated displays containing a rectangular-wave grating and a serrated aperture. In Experiment 1, infants were presented with a pair of displays: a two-dimensional to three-dimensional (2D-3D) display, alternating between 2D and 3D images, and a 2D-2D display, alternating between two 2D images. The 3D image consisted of black-and-white borders aligned with the peaks of a serrated aperture, creating the appearance of a 3D folded surface. The 2D image consisted of the black-and-white borders misaligned with the peaks of a serrated aperture, which does not create a 3D impression for adults. Seven-and 8-month-old infants looked longer at the 2D-3D display than the 2D-2D display. In contrast, 5-and 6-month-old infants did not exhibit a looking preference. In Experiment 2, we used images with double-cycle rectangular-wave gratings to impair shading information. These images consisted of blackand-white borders aligned with half of the peaks and misaligned with latter half of the peaks of a serrated aperture, giving the appearance of surface markings. Seven-and 8-month-old infants did not exhibit a significant difference in preference between the two test displays. These results could not be explained by the young infant's failure of discrimination due to the experimental procedure (Experiment 3). These results showed that the sensitivity to shading and line junctions change between 5-6 and 7-8 months of age.

Research paper thumbnail of Strength and variability of the backscroll illusion

Vision Research, 2009

When a walking person is presented in a movie, the background image appears to move in a directio... more When a walking person is presented in a movie, the background image appears to move in a direction opposite to that of the person's locomotion. This study aimed to quantify the strength of this backscroll illusion and to examine interobserver and intraobserver variability. Stimuli were movie clips that presented a walking person in profile against a background of dynamic grating composed of two vertical sinusoidal gratings moving in opposite directions. Employing a motion-nulling method, we controlled the ratio of luminance contrasts of the component gratings to determine points that canceled the percept of unidirectional motion in the grating background. Results across 50 observers showed that the backscroll illusion disappeared when a luminance contrast of moving grating components consistent with a walker's direction was about twice as high as that for the opposite motion direction. Intraobserver variability was relatively small. However, nulling points for individual observers were more variable under conditions with dynamically moving walkers than conditions presenting only a static picture of a walker. We speculated on the underlying mechanisms of the backscroll illusion in relation to similar phenomena.

Research paper thumbnail of A continuously lit stimulus is perceived to be shorter than a flickering stimulus during a saccade

Spatial Vision, 2005

When subjects made a saccade across a single-flashed dot, a flickering dot or a continuous dot, t... more When subjects made a saccade across a single-flashed dot, a flickering dot or a continuous dot, they perceived a dot, an array (phantom array), or a line (phantom line), respectively. We asked subjects to localize both endpoints of the phantom array or line and calculated the perceived lengths. Based on the findings of Matsumiya and Uchikawa , we predicted that the apparent length of the phantom line would be larger than that of the phantom array. In Experiment 1 of the current study, contrary to the prediction, the phantom line was found to be shorter than the phantom array. In Experiment 2, we investigated whether the function underlying the filled-unfilled space illusion (Lewis, 1912) instead of the function underlying the saccadic compression could explain the results. Subjects were asked to localize both endpoints of a line or an array while keeping their eyes fixated. Although the results of Experiment 2 showed that the perceived length of a line was shorter than that of an array, the function underlying the filled-unfilled illusion could not fully account for the results of Experiment 1. To explain the present results, we proposed a model for the localization process and discussed its validity.

Research paper thumbnail of Inhibitory Tagging on Randomly Moving Objects

Psychological Science, 2002

Inhibitory tagging is a process that prevents focal attention from revisiting previously checked ... more Inhibitory tagging is a process that prevents focal attention from revisiting previously checked items in inefficient searches, facilitating search performance. Recent studies suggested that inhibitory tagging is object rather than location based, but it was unclear whether inhibitory tagging operates on moving objects. The present study investigated the tagging effect on moving objects. Participants were asked to search for a moving target among randomly and independently moving distractors. After either efficient or inefficient search, participants performed a probe detection task that measured the inhibitory effect on search items. The inhibitory effect on distractors was observed only after inefficient searches. The present results support the concept of object-based inhibitory tagging.

Research paper thumbnail of MISMATCH NEGATIVITY RELATED TO UPDATING INFORMATION IN OBJECT FILES

PSYCHOLOGIA -An International Journal of Psychology in the Orient, 2005

Research paper thumbnail of Smooth Pursuit Eye Movements Improve Temporal Resolution for Color Perception

PLoS ONE, 2010

Human observers see a single mixed color (yellow) when different colors (red and green) rapidly a... more Human observers see a single mixed color (yellow) when different colors (red and green) rapidly alternate. Accumulating evidence suggests that the critical temporal frequency beyond which chromatic fusion occurs does not simply reflect the temporal limit of peripheral encoding. However, it remains poorly understood how the central processing controls the fusion frequency. Here we show that the fusion frequency can be elevated by extra-retinal signals during smooth pursuit. This eye movement can keep the image of a moving target in the fovea, but it also introduces a backward retinal sweep of the stationary background pattern. We found that the fusion frequency was higher when retinal color changes were generated by pursuit-induced background motions than when the same retinal color changes were generated by object motions during eye fixation. This temporal improvement cannot be ascribed to a general increase in contrast gain of specific neural mechanisms during pursuit, since the improvement was not observed with a pattern flickering without changing position on the retina or with a pattern moving in the direction opposite to the background motion during pursuit. Our findings indicate that chromatic fusion is controlled by a cortical mechanism that suppresses motion blur. A plausible mechanism is that eye-movement signals change spatiotemporal trajectories along which color signals are integrated so as to reduce chromatic integration at the same locations (i.e., along stationary trajectories) on the retina that normally causes retinal blur during fixation.

Research paper thumbnail of Global interference: The effect of exposure duration that is substituted for spatial frequency

Perception, 2002

In this study, participants were required to identify hierarchically structured patterns that app... more In this study, participants were required to identify hierarchically structured patterns that appeared at either global or local level. Paquet and Merikle (1984 Canadian Journal of Psychology 381 45-53) showed that global interference is affected by exposure duration in the processing of a hierarchical structure. They showed that only global-to-local interference occurred at short exposure durations. In contrast, global-to-local as well as local-to-global interference was observed at long exposure durations. They suggested that the effect of exposure duration with global interference depends on the high-spatial-frequency versus low-spatial-frequency channel. In the present study, exposure duration (short or long) was varied randomly from trial to trial (experiment 1), or held constant (experiment 2). In experiment 1, global-to-local interference occurred at both short and long exposure durations, even though the same physical properties existed as in experiment 2. In experiment 2, both global-to-local and local-to-global interference occurred at only long exposure durations, in line with the results reported by Paquet and Merikle. This suggests that the effect of exposure duration on global interference is explained not only by spatial-frequency channels, but also by attentional shift.

Research paper thumbnail of Biological motion alters coherent motion perception

Perception, 2008

When a movie presents a person walking, the background appears to move in the direction opposite ... more When a movie presents a person walking, the background appears to move in the direction opposite to the person's gait. This study verified this backscroll illusion by presenting a point-light walker against a background of a random-dot cinematogram (RDC). The RDC consisted of some signal dots moving coherently either leftward or rightward among other noise dots moving randomly. The method of constant stimuli was used to vary the RDC in motion coherence from trial to trial by manipulating the direction and percentage of the signal dots. Six observers judged the perceived direction of coherent motion in a two-alternative forced-choice procedure. Response rates for coherent motion perception in the direction opposite to walking were evaluated as a function of motion coherence. The results showed that the psychometric function shifted toward the direction determined by a bias in the opposite direction to the walker. The mean threshold was about half as high as that in a control condition in which the positions of the point-lights were scrambled to impair the recognition of the walker. The results demonstrate that biological motion noticeably affects the appearance of motion coherence in the background.

Research paper thumbnail of Reduction of stimulus visibility compresses apparent time intervals

Nature Neuroscience, 2008

The neural mechanisms underlying visual estimation of subsecond durations remain unknown, but per... more The neural mechanisms underlying visual estimation of subsecond durations remain unknown, but perisaccadic underestimation of interflash intervals may provide a clue as to the nature of these mechanisms. Here we found that simply reducing the flash visibility, particularly the visibility of transient signals, induced similar time underestimation by human observers. Our results suggest that weak transient responses fail to trigger the proper detection of temporal asynchrony, leading to increased perception of simultaneity and apparent time compression.

Research paper thumbnail of The pointedness effect on representational momentum

Memory & Cognition, 2001

An observer's memory for the final position of a moving object is shifted forward in the directio... more An observer's memory for the final position of a moving object is shifted forward in the direction of that object's motion. It is called representational momentum (RM). This study addressed stimulusspecific effects on RM. In Experiment 1, participants showed larger memory shift for an object moving in its typical direction of motion than when it moved in a nontypical direction of motion. In Experiment 2, participants indicated larger memory shift for a pointed pattern moving in the direction of its point than when it moved in the opposite direction. In Experiment 3, we again examined the influences of knowledge about objects' typical motions and the pointedness of objects, because we did not control the shape (pointedness) of objects in Experiment 1. The results showed that only pointedness affected the magnitude of memory shift and that the effect was smaller than the momentum effect.

Research paper thumbnail of Perception of motion trajectory from the moving cast shadow in human infants

Research paper thumbnail of Priming effects in multiple object tracking: An implicit encoding based on global spatiotemporal information

Research paper thumbnail of Asymmetry in the detection of shapes from shading in infants 1

Japanese Psychological Research, 2008

ABSTRACT