Head Rotation Movement Times

Serial dependencies in visual stability during self-motion

Every time we move our head, the brain must decide whether the displacement of the visual scene is the result of external or self-produced motion. Gaze shifts generate the biggest and most frequent disturbance of vision. Visual stability during gaze shifts is necessary for both, dissociating self-produced from external motion and retaining bodily balance. Here, we asked participants to perform an eye-head gaze shift to a target that was briefly presented in a head-mounted display. We manipulated the velocity of the scene displacement across trials such that the background moved either too fast or too slow in relation to the head movement speed. Participants were required to report whether they perceived the gaze-contingent visual motion as faster or slower than what they would expect from their head movement velocity. We found that the point of visual stability was attracted to the velocity presented in the previous trial. Our data reveal that serial dependencies in visual stability calibrate the mapping between motor-related signals coding head movement velocity and visual motion velocity. This process is likely to aid in visual stability as the accuracy of this mapping is crucial to maintain visual stability during self-motion.NEW & NOTEWORTHY We report that visual stability during self-motion is maintained by serial dependencies between the current and the previous gaze-contingent visual velocity that was experienced during a head movement. The gaze-contingent scene displacement velocity that appears normal to us thus depends on what we have registered in the recent history of gaze shifts. Serial dependencies provide an efficient means to maintain visual stability during self-motion.

Head movement and its relation to hearing

Head position at any point in time plays a fundamental role in shaping the auditory information that reaches a listener, information that continuously changes as the head moves and reorients to different listening situations. The connection between hearing science and the kinesthetics of head movement has gained interest due to technological advances that have increased the feasibility of providing behavioral and biological feedback to assistive listening devices that can interpret movement patterns that reflect listening intent. Increasing evidence also shows that the negative impact of hearing deficits on mobility, gait, and balance may be mitigated by prosthetic hearing device intervention. Better understanding of the relationships between head movement, full body kinetics, and hearing health, should lead to improved signal processing strategies across a range of assistive and augmented hearing devices. The purpose of this review is to introduce the wider hearing community to the kinesiology of head movement and to place it in the context of hearing and communication with the goal of expanding the field of ecologically-specific listener behavior.

Temporal perturbations cause movement-context independent but modality specific sensorimotor adaptation

Complex, goal-directed and time-critical movements require the processing of temporal features in sensory information as well as the fine-tuned temporal interplay of several effectors. Temporal estimates used to produce such behavior may thus be obtained through perceptual or motor processes. To disentangle the two options, we tested whether adaptation to a temporal perturbation in an interval reproduction task transfers to interval reproduction tasks with varying sensory information (visual appearance of targets, modality, and virtual reality [VR] environment or real-world) or varying movement types (continuous arm movements or brief clicking movements). Halfway through the experiments we introduced a temporal perturbation, such that continuous pointing movements were artificially slowed down in VR, causing participants to adapt their behavior to sustain performance. In four experiments, we found that sensorimotor adaptation to temporal perturbations is independent of environment context and movement type, but modality specific. Our findings suggest that motor errors induced by temporal sensorimotor adaptation affect the modality specific perceptual processing of temporal estimates.

Sensorimotor serial dependencies in head movements

On average, we redirect our gaze with a frequency at about 3 Hz. In real life, gaze shifts consist of eye and head movements. Much research has focused on how the accuracy of eye movements is monitored and calibrated. By contrast, little is known about how head movements remain accurate. I wondered whether serial dependencies between artificially induced errors in head movement targeting and the immediately following head movement might recalibrate movement accuracy. I also asked whether head movement targeting errors would influence visual localization. To this end, participants wore a head mounted display and performed head movements to targets, which were displaced as soon as the start of the head movement was detected. I found that target displacements influenced head movement amplitudes in the same trial, indicating that participants could adjust their movement online to reach the new target location. However, I also found serial dependencies between the target displacement in trial n-1 and head movements amplitudes in the following trial n. I did not find serial dependencies between target displacements and visuomotor localization. The results reveal that serial dependencies recalibrate head movement accuracy.

Beyond Fitts's Law: A Three-Phase Model Predicts Movement Time to Position an Object in an Immersive 3D Virtual Environment

OBJECTIVE

The study examines the factors determining the movement time (MT) of positioning an object in an immersive 3D virtual environment.

BACKGROUND

Positioning an object into a prescribed area is a fundamental operation in a 3D space. Although Fitts's law models the pointing task very well, it does not apply to a positioning task in an immersive 3D virtual environment since it does not consider the effect of object size in the positioning task.

METHOD

Participants were asked to position a ball-shaped object into a spherical area in a virtual space using a handheld or head-tracking controller in the ray-casting technique. We varied object size (OS), movement amplitude (A), and target tolerance (TT). MT was recorded and analyzed in three phases: acceleration, deceleration, and correction.

RESULTS

In the acceleration phase, MT was inversely related to object size and positively proportional to movement amplitude. In the deceleration phase, MT was primarily determined by movement amplitude. In the correction phase, MT was affected by all three factors. We observed similar results whether participants used a handheld controller or head-tracking controller. We thus propose a three-phase model with different formulae at each phase. This model fit participants' performance very well.

CONCLUSION

A three-phase model can successfully predict MT in the positioning task in an immersive 3D virtual environment in the acceleration, deceleration, and correction phases, separately.

APPLICATION

Our model provides a quantitative framework for researchers and designers to design and evaluate 3D interfaces for the positioning task in a virtual space.