The sense of agency refers to an experience in which one’s own action causes a change in environment. It is strongly modulated by both the contingency between action and its outcome and the consistency between predicted and actual action outcomes. Recent studies have suggested that the action outcome can retrospectively modulate action awareness. We suspect that the sense of agency can also be retrospectively modulated. This study examined whether the quantity of action outcome could influence the sense of agency. The (...) participants’ task was to trigger dot motion in a display and rate the extent to which they could control the initiation of dot motion. Independently of both the temporal contiguity between action and its outcome and the consistency between predicted and actual action outcomes, the speed of dot motion as an action’s outcome strongly influenced the sense of agency rating. The present study suggests that the sense of agency stems partly from the inference of action efficiency based on the quantitative aspect of action outcome. (shrink)

Emotion modulates our time perception. So far, the relationship between emotion and time perception has been examined with visible emotional stimuli. The present study investigated whether invisible emotional stimuli affected time perception. Using continuous flash suppression, which is a kind of dynamic interocular masking, supra-threshold emotional pictures were masked or unmasked depending on whether the retinal position of continuous flashes on one eye was consistent with that of the pictures on the other eye. Observers were asked to reproduce the perceived (...) duration of a frame stimulus that was concurrently presented with a masked or unmasked emotional picture. As a result, negative emotional stimuli elongated the perceived duration of the frame stimulus in comparison with positive and neutral emotional stimuli, regardless of the visibility of emotional pictures. These results suggest that negative emotion unconsciously accelerates an internal clock, altering time perception. (shrink)

When an elastic material is horizontally stretched, the material is compressed vertically – so-called the Poisson effect. In the different case of the Poisson effect, when an elastic material is vertically squashed, the material is horizontally extended. In both cases, the visual system receives image deformations involving horizontal expansion and vertical compression. How does the brain disentangle the two cases and accurately distinguish stretching from squashing events? Manipulating the relative magnitude of the deformation of a square between horizontal and vertical (...) dimensions in the two-dimensional stimuli, we asked observers to judge the force direction in the stimuli. Specifically, the participants reported whether the square was stretched or squashed. In general, the participant’s judgment was dependent on the relative deformation magnitude. We also checked the anisotropic effect of deformation direction [i.e., horizontal vs. vertical stretching ] and found that the participant’s judgment was strongly biased toward horizontal stretching. We also observed that the asymmetric deformation pattern, which indicated the specific context of force direction, was also a strong cue to the force direction judgment. We suggest that the brain judges the force direction in the Poisson effect on the basis of assumptions about the relationship between image deformation and force direction, in addition to the relative image deformation magnitudes between horizontal and vertical dimensions. (shrink)

Haptic sensation of a material can be modulated by its visual appearance. A technique that utilizes this visual-haptic interaction is called as pseudo-haptic feedback. Conventional studies have investigated pseudo-haptic feedback in situations, wherein a user manipulated a virtual object using a computer mouse, a force-feedback device, etc. The present study investigated whether and how it was possible to offer pseudo-haptic feedback to a user who manipulated a virtual object using keystrokes. Participants moved a cursor toward a destination by pressing a (...) key. While the cursor was moving, the cursor was temporarily slowed down on a square area of the screen. The participants’ task was to report, on a five-point scale, how much resistance they felt to the cursor’s movement. In addition to the basic speed of the cursor, the ratio of the basic speed to the speed within the square area was varied. In Experiment 1, we found that these two factors interacted significantly with each other, but further analysis showed that the cursor speed within the square area was the most important determinant of perceived resistance. In Experiment 2, consistent with the results of the previous experiment, it was found that the cursor movement outside of the square area was not required to generate the sense of resistance. Counterintuitively, in Experiment 3, the sense of resistance was apparent even without user’s keystrokes. We discuss how the sense of resistance for a cursor moved by keystrokes can be triggered visually, but interpreted by the brain as a haptic impression. (shrink)

Interaction systems with gesture-based touchless inputs are becoming more common. Nevertheless, perceptual properties of the visual feedback used in the system have not been well documented. We investigated whether the speed of motion shown in visual feedback used in gesture-based touchless inputs could be a cue for the heaviness sensation of an object even when other incidental cues, such as changes in object size and spatial consistencies in direction between gestures and feedback, were eliminated from the stimuli. Participants were asked (...) to make a gesture to grasp and raise/lower disks shown on a horizontal display. The disk’s diameter changed in accordance with the vertical position of the participant’s hand. The results showed that the rate of change in diameter determined the heaviness sensation. When the disks were replaced with concentric gratings having sinusoidal radial intensity and thus the cue of size change was eliminated from the stimuli, the heaviness sensation was dependent on the speed of phase shift in the grating. It was also found that spatial consistency between the direction of gestures and phase shift was not a critical condition for the heaviness sensation. Finally, the speed of motion served as a critical determinant of the heaviness sensation even when another visual feature was modulated in a single session, which indicates that the effect of the speed of motion on the heaviness sensation was unlikely due to demanded characteristics. The results indicate that the heaviness sensation for visual feedback of gesture-based touchless inputs is based purely on the speed of the visual feedback motion. (shrink)

SummaryVisual acuity was tested and the anterior portion of the eye inspected among the Gidra in Lowland Papua New Guinea, who depend on hunting for their animal food. The visual acuity of the youths and adults was as high as that of hunters and gatherers; 88% of the males and 81% of the females had an acuity of 1·2 or better. The elders had far lower acuity, correlated with the advance of cataract. The senescent visual acuity is discussed in relation (...) to little practice and low productivity of the elders' hunting, and to the Gidra traditional age-grade system. (shrink)

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 . Second, we examined whether the observers could correctly respond to the direction of invisible motion: It was impossible. (shrink)

In motion-induced blindness , 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 . 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 (...) 1 Hz hindered MIB when the radius of the cue was critically small . Furthermore, abrupt onset of a small square was enough to regain awareness of the target . 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. (shrink)