Visual contribution to human standing balance during support surface tilts

Visual position and velocity cues improve human standing balance, reducing sway responses to external disturbances and sway variability. Previous work suggested that human balancing is based on sensory estimates of external disturbances and their compensation using feedback mechanisms (Disturbance Estimation and Compensation, DEC model). This study investigates the visual effects on sway responses to pseudo-random support surface tilts, assuming that improvements result from lowering the velocity threshold in a tilt estimate and the position threshold in an estimate of the gravity disturbance. Center of mass (COM) sway was measured with four different tilt amplitudes, separating the effect of visual cues across the conditions ‘Eyes closed’ (no visual cues), ‘4 Hz stroboscopic illumination’ (visual position cues), and ‘continuous illumination’ (visual position and velocity cues). In a model based approach, parameters of disturbance estimators were identified. The model reproduced experimental results and showed a specific reduction of the position and velocity threshold when adding visual position and velocity cues, respectively. Sway variability was analyzed to explore a hypothesized relation between estimator thresholds and internal noise. Results suggest that adding the visual cues reduces the contribution of vestibular noise, thereby reducing sway variability and allowing for lower thresholds, which improves the disturbance compensation.     

Attention AND mentalizing? Reframing a debate on social orienting of attention

ABSTRACT

People spontaneously attend where others are looking. Recently, it has been debated whether such orienting behaviour is supported by domain-general attentional processes, that involve reading the cues’ directional properties, or by processes that involve attributing mental states to agents. In this Opinion, we summarize key evidence for each position and argue that instead of favouring one or the other view, the available data point to an integrated framework in which the attribution of mental states and the operation of domain-general attentional processes both contribute to social orienting. In addition to providing a novel perspective, this view opens several fruitful future research avenues aimed at understanding how the two processes act together to influence cognitions and behaviour.