Department of psychology


– Postural Control

Postural Control

The postural control system has two main functions: first, to build up posture against gravity and ensure that balance is maintained; and second, to fix the orientation and position of the segments that serve as a reference frame for perception and action with respect to the environment. This dual function of postural control is based on multisensory inputs regulating orientation and stabilization of body segments; and flexible postural anticipations for balance recovery after disturbance, or postural stabilization during voluntary movement.

Auditory Guided Rotation

Choosing the Shortest Way to Mum: Auditory Guided Rotation in 6- to 9-month-old infants

by Van der Meer, Ramstad &Van der Weel
The purpose of this study was to investigate the use of auditory information for rotation of the shortest way in twelve 6- to 9-month-old sighted infants. Behaviour was manipulated by means of an auditory stimulus presented in four different directional angles (90◦, 112.5◦, 135◦, and 157.5◦) to the right and to the left behind the infants, and in one non-directional angle (180◦). Infants lay in a prone position and had magnetic trackers fastened to the head and body which measured their rotation direction and angular velocity. The results showed that infants not only consistently chose the shortest over the longest way, but also rotated with a higher peak angular velocity as the angle to be covered between themselves and the goal increased. The results did not show significant preferences for one particular rotation direction. The study can contribute to the understanding of the auditory system as a functional listening system where auditory information is used as a perceptual source for prospectively guiding behaviour in the environment.

Affordance of Ducking

Visual Guidance of Passing Under a Barrier

by Van der Meer

The theory of affordances proposes that organisms control their actions according to the fit between the organism and the environment. This study set out to examine the proposal that actions are attuned to environmental demands on the basis of body-scaled information and how modifications to such actor-
environment synergies might be influenced by the speed of locomotion and locomotor ability. The paradigm task was walking and running under a barrier set at different heights. The subject groups comprised normal adults, nursery school children, cerebral palsied children, and infants with less than 6 weeks' independent walking experience. A body-scaled critical point, at which they
began to duck under the barrier, was observed for all but the infant subjects. In addition, the nursery school children were found to be more cautious in their behaviour than adults both when walking and running. The cerebral palsied children compensated for their poorer ability to control vertical position in space by allowing an even greater safety margin when passing under the barrier. The results provide support for an affordance theory of perception, in which body size, speed of locomotion and
level of motor control are considered important properties of the actor-environment fit.


Prospective Dynamic Balance Control in Healthy Children and Adults

by Austad & Van der Meer

Balance control during gait initiation was studied using center of pressure (CoP) data from force plate measurements. Twenty-four participants were divided into four age groups: (1) 2–3 years, (2) 4–5 years, (3) 7–8 years, and (4) adults. Movement in the anteroposterior (CoPy) direction during the initial step was tau-G analyzed, investigating the hypothesis that tau of the CoPy motion-gap (CoPy), i.e., the time it will take to close the gap at its current closure rate, is tau-coupled onto an intrinsic tau-G guide ( G), by maintaining the relation CoPy = K G, for a constant K. Mean percentage of tau-guidance for all groups was ¸99%, resulting in all r² exceeding 0.95, justifying an investigation of the regression slope as an estimate of the
coupling constant K in the tau-coupling equation. Mean K values decreased significantly with age and were for 2- to 3-year-olds 0.56, for 4- to 5-year-olds 0.50, for 7- to 8-year olds 0.47, and for adults 0.41. Therefore, the control of dynamic balance develops from the youngest children colliding with the boundaries of the base of support (K > 0.5) to the older children and adults making touch contact (K <= 0.5). The findings may provide us with a measure for testing prospective balance control, a helpful tool in assessing whether a child is following a normal developmental pattern.