Yuko Masakura

Reduction of the flash-lag effect in terms of active observation

In the present study, we investigated how observers’ control of stimulus change affects temporal and spatial aspects of visual perception. We compared the illusory flash-lag effects for automatic movement of the stimulus with stimulus movement that was controlled by the observers’ active manipulation of a computer mouse (Experiments 1, 2, and 5), a keyboard (Experiment 3), or a trackball (Experiment 4). We found that the flash-lag effect was significantly reduced when the observer was familiar with the directional relationship between the mouse movement and stimulus movement on a front parallel display (Experiments 1 and 2) and that, although the unfamiliar directional relationship between the mouse movement and stimulus movement increased the flash-lag effect at the beginning of the experimental session, the repetitive observation with the same unfamiliar directional relationship reduced the flash-lag effect (Experiment 5). We found no consistent reduction of the flash-lag effect with the use of a keyboard or a trackball (Experiments 3 and 4). These results suggest that the learning of a specific directional relationship between a proprioceptive signal of hand movements and a visual signal of stimulus movements is necessary for the reduction of the flash-lag effect.

Dependence of illusory motion on directional consistency in oblique components

Pinna and Brelstaff (2000 Vision Research 40 2091–2096) reported a motion illusion on viewing two concentric circles consisting of quadrangular components with black and white sides on a grey background. Our results suggest that the illusion is based on the integration of motion signals derived from oblique components, and on the consistency in the direction among those components. Furthermore, arrays of these oblique components can elicit the perception of motion not only for the oblique components themselves, but also for other objects in the picture. We propose that the motion illusion depends not only upon detection of the illusory motion signal at each local oblique component, but also upon the accumulation of the signal all over the stimulus configuration.

Effects of consciousness and consistency in manual control of visual stimulus on reduction of the flash-lag effect for luminance change.

Four experiments investigated how observers’ consciousness about their control of stimulus change affects the visual perception associated with the illusory flash-lag effect. In previous study (Ichikawa and Masakura, 2006), we found that the flash-lag effect in motion is reduced if observers were conscious that they were controlling stimulus movements by the use of computer mouse, even if the stimulus moved automatically, independently of observer’s mouse control. In the other study (Ichikawa and Masakura, 2010a), we found that the consistent directional relationship between the observer’s mouse control and stimulus movement, which is learned in our everyday computer use, is important for the reduction of the flash-lag effect in active observation. In the present study, we examined whether the reduction of the flash-lag effect in active observation requires the observers’ consciousness about their control of stimulus change, and consistency in coupling mouse movement direction and stimulus change across trials in experiments. We used the flash-lag effect in luminance change because there is no intrinsic relationship between observer’s mouse control and luminance change in our everyday computer use. We compared the illusory flash-lag effects for automatic change of the luminance with luminance change that was controlled by the observers’ active manipulation of a computer mouse. Because the flash occurs randomly in time, observers could not anticipate when the flash was presented. Results suggest that the not only observer’s consciousness of controlling the stimulus, but also consistency in coupling mouse movement direction with stimulus change, are required for the reduction of the flash-lag effect in active observation. The basis of the reduction of the flash-lag effect in active observation is discussed.

Basis for Motion Capture in Terms of Illusory Motion Signal Obtained from Oblique Lines

As in the Pinna illusion, when an observer moves their head backwards and forwards while fixating on the center of concentric circles that consist of oblique lines, the observer sees illusory rotation of those circles. When several dots are superimposed on the concentric circles, an observer sees the illusory rotation not only for the circles, but also for those dots (Ichikawa, Masakura, & Munechika, 2006, Perception, 35, 933–946). This illusory rotation of the dots, which have no means of generating illusory motion themselves, is based on motion capture. We examined how the number of dots affects the illusory rotation for such circles and superimposed dots. Results showed that the illusory rotation for the inner circle was most salient when the superimposed dots were extremely numerous or few, although the illusory motion for the dots increased with the increment of the dots. These results suggest that motion capture depends upon a locally obtained motion signal from the oblique lines, and upon the accumulation of the motion signal within the groups of superimposed dots.

Motion Capture Depends Upon the Common Fate Factor Among Elements

When observers move the head backwards and forwards while fixating on the center of the concentric circles that consist of oblique lines, they see illusory rotation of those circles. If several dots are superimposed on the proximity to the inner concentric circles, observers see the illusory rotation not only for the circles but also for the superimposed dots. This illusory rotation of the dots is based on motion capture. In this study, in order to understand the basis of the motion capture, we examined how motion signal with different directions (rotation, expansion/contraction, and horizontal translation) in terms of motion on a display, as well as illusory motion signal from the oblique components, affects the motion capture. If the stimulus presented rotation with expansion/contraction, or rotation with horizontal translation for the entire stimulus, then observers tended to perceive motion capture for the superimposed dots. However, if the stimulus presented only rotation of the circles, then observers tended to perceive induced motion for the superimposed dots. These results suggest that the existences of the common fate factor for the entire stimulus determine the means of allocating and integrating the motion signal in each element in the stimulus to generate motion capture.

Visual Presentation Effects on Identification of Multiple Environmental Sounds

This study examined how the contents and timing of a visual stimulus affect the identification of mixed sounds recorded in a daily life environment. For experiments, we presented four environment sounds as auditory stimuli for 5 s along with a picture or a written word as a visual stimulus that might or might not denote the source of one of the four sounds. Three conditions of temporal relations between the visual stimuli and sounds were used. The visual stimulus was presented either: (a) for 5 s simultaneously with the sound; (b) for 5 s, 1 s before the sound (SOA between the audio and visual stimuli was 6 s); or (c) for 33 ms, 1 s before the sound (SOA was 1033 ms). Participants reported all identifiable sounds for those audio–visual stimuli. To characterize the effects of visual stimuli on sound identification, the following were used: the identification rates of sounds for which the visual stimulus denoted its sound source, the rates of other sounds for which the visual stimulus did not denote the sound source, and the frequency of false hearing of a sound that was not presented for each sound set. Results of the four experiments demonstrated that a picture or a written word promoted identification of the sound when it was related to the sound, particularly when the visual stimulus was presented for 5 s simultaneously with the sounds. However, a visual stimulus preceding the sounds had a benefit only for the picture, not for the written word. Furthermore, presentation with a picture denoting a sound simultaneously with the sound reduced the frequency of false hearing. These results suggest three ways that presenting a visual stimulus affects identification of the auditory stimulus. First, activation of the visual representation extracted directly from the picture promotes identification of the denoted sound and suppresses the processing of sounds for which the visual stimulus did not denote the sound source. Second, effects based on processing of the conceptual information promote identification of the denoted sound and suppress the processing of sounds for which the visual stimulus did not denote the sound source. Third, processing of the concurrent visual representation suppresses false hearing.

Analysis of music appreciation by Kansei evaluation and brain activity

Music has an effect altering the feeling of the listener. Currently, several researches challenged to manifest the effect of music on the listeners. Previous study revealed that frontal lobe plays an important role for music appreciation. Based on this finding, this study attempted to classify genre (category) of music pieces and knowingness/unknowingness of them based on Kansei evaluation and brain activity of frontal lobe obtained from NIRS. Furthermore, we attempted to explain impression of music from brain activity. As a result, discrimination rate about knowingness of music achieved 87%. In genre discrimination, the discrimination rate became high if data for discrimination were restricted to known music. We can conclude that it is possible to infer subjects knowingness about music and genre of music from cerebral blood data.

Effect of Denotative Congruency on Pleasant Impressions for Audio-Visual Stimuli

We examined how the denotative congruency (Masakura & Ichikawa, 2003) in audio-visual stimuli affects the pleasant and restful impressions for the stimuli. In Experiment 1, a single sound was combined with a single motion picture. Results showed that the pleasant and restful impressions for the combined audio-visual stimuli determined by averaging the impressions obtained from each of audio and visual stimuli. In Experiment 2, two sounds were combined with a single motion picture. Results showed that the pleasant and restful impressions positively shifted when one of the sounds was combined with a denotatively congruent motion picture, even if the unpleasant and unrestful sound was combined with unpleasant and unrestful motion picture. These results suggested that the denotative congruency between the audio and visual stimuli would exaggerate pleasant and restful impressions. Reduction of stimulus complexity is expected to lead to exaggeration of pleasant impression (Berlyne, 1970). We are proposing that the reduction of the stimulus complexity underlie the exaggerating effect of denotative congruency on the pleasant and restful impressions in observing the audio-visual stimuli.

Effects of Proprioceptive Processing on the Illusory Flash-Lag Effect in Motion and Luminance Change

Observers active control of visual stimulus movement by the use of computer mouse reduces the flash-lag effect (Ichikawa & Masakura, 2006, Vision Research). This reduction of the flash-lag effect in visual motion depends upon directional relationship between hand movement and visual stimulus movement (Ichikawa & Masakura, 2010 AP&P). These studies indicate that the reduction of the flash-lag effect depends upon the sensory-motor learning of the directional consistency between the hand movement and stimulus movement in everyday-computer use. In this study, we examined how directional relationship between hand movement and stimulus change, which is not involved in every-computer use, affects the reduction of the flash-lag effect if there is no inevitable directional relationship between hand movement and stimulus change. While the luminance of the visual stimulus was controlled by the use of computer-mouse, a flash was presented. Observer judged which of the flash and luminance change stimulus is lighter. We found significant reduction of the flash-lag effect only when the directional relationship between hand movement and stimulus change was fixed. The results suggest that the proprioceptive signal to control the visual stimulus would facilitate the visual processing if the directional relationship between hand movement and stimulus change is consistent.

P-48: Quantitative Evaluation Method for the White Uniformity of a Large-Sized LED Backlight

We report the results of viewer perception of the degree of the white uniformity of LED backlight and photometric data measured by a 2D colorimeter. We propose a multiple regression model in order to provide a more dependable check on the uniformity of LED backlights.