Inferring sense of agency from the quantitative aspect of action outcome

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.     

Audiovisual tau effect

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.     

New motion illusion caused by pictorial motion lines

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.     

State-dependent corrective reactions for backward balance losses during human walking

We investigated corrective reactions for backward balance losses during walking. Several biomechanical studies have suggested that backward falling can be predicted from the horizontal position and velocity of the body center of mass (COM) related to the stance foot. Our hypothesis was that corrective reactions for backward balance losses depend on whether the body moves forward or backward after a perturbation. Using a split-belt treadmill, backward balance losses during walking were induced by rapid decreases of belt speed from 3.5 km/h to 2.5, 2.0, 1.5 and 1.0 km/h. We measured kinematic data and surface electromyography (EMG) during corrective reactions while walking on the treadmill. Phase portrait analysis of COM trajectories revealed that backward balance stability was decreased by the perturbations. When the perturbed belt speed was 1.0 km/h, the COM states at toe-off were significantly lower than the stability limit; a rapid touch-down of the swing foot posterior to the stance foot then occurred, and the gait rhythm was modulated so that the phase advanced. EMG recordings during perturbed steps revealed a bilateral response, including modulation of the swing leg during the recovery. For weaker perturbations, the swing foot placements were anterior to the stance foot and there was a phase delay. In contrast to the bilateral responses for stronger perturbations, unilateral EMG responses were observed for weaker perturbations. The differences in joint kinematics and EMG patterns in the unperturbed swing leg depended on the COM states at toe-off, suggesting the existence of different responses consisting of ongoing swing movements and rapid touch-down. Thus, we conclude that corrective reactions for backward balance losses are not only phase-dependent but also state-dependent. In addition, the control system for backward balance losses predicts the feasibility of forward progression and modulates swing movement and walking rhythm according to backward balance stability.     

Invisible motion contributes to simultaneous motion contrast

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).     

Conscientiousness mediates the relation between perceived parental socialisation and self-rated health

The pathways between parenting behaviours, personality and physical health have all been separately studied. Prior research has paid little attention to the indirect effects of personality in the path between parenting behaviours and better health. The purpose of this study was to explore the mediational effects of conscientiousness on the relationships between parental socialisation of responsibility and self-rated health, and to examine potential age differences in this mediational pathway. In total, 736 female and 749 male members across Japan participated in this study. They were divided into three groups by age category: younger-, middle-aged and older-aged. Conscientiousness and health were concurrently rated, while parental socialisation of responsibility was retrospectively assessed. Our analyses revealed that parental socialisation of responsibility is positively associated with conscientiousness and self-rated health, that conscientiousness is positively associated with self-rated health, and that conscientiousness fully mediated the effect of parental socialisation of responsibility on self-rated health. The mediational links were consistent across younger, middle-aged and older-aged cohorts. Our findings suggest that greater parental socialisation of responsibility relates to higher conscientiousness, and consequently healthier adults. These findings imply that parental behaviours could be a plausible target for intervention to foster the development of conscientiousness and better health.     

Slower Reorientation of Trunk for Reactive Turning while Walking in Hemiparesis Stroke Patients

We examined the behavioral characteristics of reactive turning in hemiplegic stroke patients when they were informed of the turning direction just before turning was required at an unpredictable time. Eleven stroke patients and 20 healthy elderly control people were asked to initiate a turn as soon as a visual cue to inform them of the turning direction was activated unpredictably using a foot switch. Both the segmental reorientation and stepping type when turning 90° while walking were measured. The results indicated preserved segmental reorientation of the head and pelvis in stroke patients. Stroke patients showed delays in pelvic turning but not in head turning. Their delayed pelvic movement might be due to motor dysfunction and the time taken to ensure stability when deciding when to turn.     

Athletic experience influences shoulder rotations when running through apertures

In order to pass through apertures safely and efficiently, individuals must perceive the width of the aperture relative to (1) the width of the person-plus-object system and to (2) their (anticipated) movement speed. The present study investigated whether athletes who have extensive experience playing sports that require running through narrow spaces while wearing shoulder pads control their shoulder rotations differently while performing this behavior than athletes who lack such experience. Groups of athletes with experience competing in different sports (American football, rugby, and control athletes) performed a behavioral task in which they ran or walked between two tucking dummies with or without wearing shoulder pads. They also performed a psychophysical task in which they reported perceived width of the body and shoulder pads. When running through the apertures, the athletes who played American football exhibited smaller magnitudes and later onset of shoulder rotations than control athletes. No such difference was found when walking through the apertures. There was no difference in perception of the width of the shoulder pads among three groups. These findings suggest that performance of this behavior is action-scaled and task-specific.     

A Propensity Score Adjustment for Multiple Group Structural Equation Modeling

In the behavioral and social sciences, quasi-experimental and observational studies are used due to the difficulty achieving a random assignment. However, the estimation of differences between groups in observational studies frequently suffers from bias due to differences in the distributions of covariates. To estimate average treatment effects when the treatment variable is binary, Rosenbaum and Rubin (1983a) proposed adjustment methods for pretreatment variables using the propensity score. However, these studies were interested only in estimating the average causal effect and/or marginal means. In the behavioral and social sciences, a general estimation method is required to estimate parameters in multiple group structural equation modeling where the differences of covariates are adjusted. We show that a Horvitz–Thompson-type estimator, propensity score weighted M estimator (PWME) is consistent, even when we use estimated propensity scores, and the asymptotic variance of the PWME is shown to be less than that with true propensity scores. Furthermore, we show that the asymptotic distribution of the propensity score weighted statistic under a null hypothesis is a weighted sum of independent χ² ₁ variables. We show the method can compare latent variable means with covariates adjusted using propensity scores, which was not feasible by previous methods. We also apply the proposed method for correlated longitudinal binary responses with informative dropout using data from the Longitudinal Study of Aging (LSOA). The results of a simulation study indicate that the proposed estimation method is more robust than the maximum likelihood (ML) estimation method, in that PWME does not require the knowledge of the relationships among dependent variables and covariates.     

Perceptual grouping in shape from shading

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.