Test–retest stability of an experimental measure of human turning behaviour in right-handers, mixed-handers, and left-handers

Smartphones and rightward collisions

People tend to deviate to the right when walking through a narrow aperture (e.g., a doorway), resulting in a rightward bias in collisions. This study examines the effects of smartphone use on rightward collisions while walking. When pedestrians walk through a narrow aperture, they usually head straight to the perceived centre of the aperture, which is shifted slightly to the right, without updating the estimates. The rightward shift of the perceived centre is attributable to the rightward attentional shift in the extrapersonal space. Pedestrians using smartphones tend to fixate on the phone most of the time and thus tend not to look at their surroundings (i.e., extrapersonal space). Therefore, we predict that smartphone use will reduce rightward collisions. To test this prediction, we used a narrow-doorway task in which participants walked through a narrow doorway either with or without a smartphone. The participants with smartphones used them to perform either verbal or spatial tasks. The number of rightward collisions decreased when the participants used smartphones. The type of task had no effect on the lateral collision biases. These results were interpreted in terms of lateral attentional bias in peripersonal and extrapersonal spaces.

An investigation of left/right driving rules on deviations while walking

When traversing through an aperture, such as a doorway, people characteristically deviate towards the right. This rightward deviation can be explained by a rightward attentional bias which leads to rightward bisections in far space. It is also possible, however, that left or right driving practices affect the deviation. To explore this possibility, Australian (left-side drivers) and Swiss (right-side drivers) participants (n = 36 & 34) walked through the middle of an aperture. To control for the sway of the body, participants started with either their left or right foot. Sway had a significant effect on participants' position in the doorway and the amount of sway was greater for Australians-perhaps due to national differences in gait. There was a significant rightward deviation for the Swiss, but not for the Australians. It is suggested that driving practices have a small additive effect on rightward attentional biases whereby the bias is increased for people who drive on the right and reduced in people who drive on the left.

Anticlockwise or clockwise? A dynamic Perception-Action-Laterality model for directionality bias in visuospatial functioning

Orientation bias and directionality bias are two fundamental functional characteristics of the visual system. Reviewing the relevant literature in visual psychophysics and visual neuroscience we propose here a three-stage model of directionality bias in visuospatial functioning. We call this model the 'Perception-Action-Laterality' (PAL) hypothesis. We analyzed the research findings for a wide range of visuospatial tasks, showing that there are two major directionality trends in perceptual preference: clockwise versus anticlockwise. It appears these preferences are combinatorial, such that a majority of people fall in the first category demonstrating a preference for stimuli/objects arranged from left-to-right rather than from right-to-left, while people in the second category show an opposite trend. These perceptual biases can guide sensorimotor integration and action, creating two corresponding turner groups in the population. In support of PAL, we propose another model explaining the origins of the biases - how the neurogenetic factors and the cultural factors interact in a biased competition framework to determine the direction and extent of biases. This dynamic model can explain not only the two major categories of biases in terms of direction and strength, but also the unbiased, unreliably biased or mildly biased cases in visuosptial functioning.

Walking in circles: a modelling approach

Blindfolded or disoriented people have the tendency to walk in circles rather than on a straight line even if they wanted to. Here, we use a minimalistic walking model to examine this phenomenon. The bipedal spring-loaded inverted pendulum exhibits asymptotically stable gaits with centre of mass (CoM) dynamics and ground reaction forces similar to human walking in the sagittal plane. We extend this model into three dimensions, and show that stable walking patterns persist if the leg is aligned with respect to the body (here: CoM velocity) instead of a world reference frame. Further, we demonstrate that asymmetric leg configurations, which are common in humans, will typically lead to walking in circles. The diameter of these circles depends strongly on parameter configuration, but is in line with empirical data from human walkers. Simulation results suggest that walking radius and especially direction of rotation are highly dependent on leg configuration and walking velocity, which explains inconsistent veering behaviour in repeated trials in human data. Finally, we discuss the relation between findings in the model and implications for human walking.

Measurement of human rotation behavior for psychological and neuropsychological investigations

The investigation of rotation behavior in human beings enjoys a longstanding and enduring interest in laterality research. While in animal studies the issue of accurately measuring the number of rotations has been solved and is widely applied in practice, it is still challenging to assess the rotation behavior of humans in daily life. We propose a robust method to assess human rotation behavior based on recordings from a miniature inertial measurement unit that can be worn unobtrusively on a belt. We investigate the effect of different combinations of low-cost sensors-including accelerometers, gyroscopes, and magnetometers-on rotation measurement accuracy, propose a simple calibration procedure, and validate the method on data from a predefined path through and around buildings. Results suggest that a rotation estimation based on the fusion of accelerometer, gyroscope, and magnetometer measurements outperforms methods based solely on earth magnetic field measurements, as proposed in previous studies, by a drop in error rate of up to 32 %. We further show that magnetometer signals do not significantly contribute to measurement accuracy in short-term measurements, and could thus be omitted for improved robustness in environments with magnetic field disturbances. Results also suggest that our simple calibration procedure can compete with more complex approaches and reduce the error rate of the proposed algorithm by up to 38 %.

Turning bias in virtual spatial navigation: age-related differences and neuroanatomical correlates

Rodents frequently exhibit rotational bias associated with asymmetry in lesions and neurotransmitters in the striatum. However, in humans, turning preference is inconsistent across studies, and its neural correlates are unclear. We examined turning bias in 140 right-handed healthy adults (18-77 years old), who navigated a virtual Morris Water Maze. On magnetic resonance images, we measured volumes of brain regions relevant to spatial navigation. We classified turns that occurred during virtual navigation as veering (less than 10°), true turns (between 10° and 90°) and course reversals (over 90°). The results showed that performance (time of platform search and distance traveled) was negatively related to age. The distance traveled was positively associated with volume of the orbito-frontal cortex but not with the volumes of the cerebellum, the hippocampus or the primary visual cortex. Examination of turning behavior showed that all participants veered to the right. In turns and reversals, although on average there was no consistent direction preference, we observed significant individual biases. Virtual turning preference correlated with volumetric asymmetry in the striatum, cerebellum, and hippocampus but not in the prefrontal cortex. Participants preferred to turn toward the hemisphere with larger putamen, cerebellum and (in younger adults only) hippocampus. Advanced age was associated with greater rightward turning preference. Men showed greater leftward preference whereas women exhibited stronger rightward bias.

Is "circling" behavior in humans related to postural asymmetry?

In attempting to walk rectilinearly in the absence of visual landmarks, persons will gradually turn in a circle to eventually become lost. The aim of the present study was to provide insights into the possible underlying mechanisms of this behavior. For each subject (N = 15) six trajectories were monitored during blindfolded walking in a large enclosed area to suppress external cues, and ground irregularities that may elicit unexpected changes in direction. There was a substantial variability from trial to trial for a given subject and between subjects who could either veer very early or relatively late. Of the total number of trials, 50% trajectories terminated on the left side, 39% on the right side and 11% were defined as “straight”. For each subject, we established a “turning score” that reflected his/her preferential side of veering. The turning score was found to be unrelated to any evident biomechanical asymmetry or functional dominance (eye, hand…). Posturographic analysis, used to assess if there was a relationship between functional postural asymmetry and veering revealed that the mean position of the center of foot pressure during balance tests was correlated with the turning score. Finally, we established that the mean position of the center of pressure was correlated with perceived verticality assessed by a subjective verticality test. Together, our results suggest that veering is related to a “sense of straight ahead” that could be shaped by vestibular inputs.