Exploring disturbance as a force for good in motor learning.

Disturbance forces facilitate motor learning, but theoretical explanations for this counterintuitive phenomenon are lacking. Smooth arm movements require predictions (inference) about the force-field associated with a workspace. The Free Energy Principle (FEP) suggests that such 'active inference' is driven by 'surprise'.

Training children aged 5-10 years in compliance control: tracing smaller figures yields better learning not specific to the scale of drawn figures.

Previously we developed a method that supports active movement generation to allow practice with improvement of good compliance control in tracing and drawing. We showed that the method allowed children with motor impairments to improve at a 3D tracing task to become as proficient as typically developing children and that the training improved 2D figure copying. In this study, we expanded the training protocol to include a wider variety of ages (5-10-year-olds) and we made the figures traced in training the same as in figure copying, but varied the scale of training and copying figures to assess the generality of learning.

Perception of time to contact of slow- and fast-moving objects using monocular and binocular motion information.

The role of the monocular-flow-based optical variable τ in the perception of the time to contact of approaching objects has been well-studied. There are additional contributions from binocular sources of information, such as changes in disparity over time (CDOT), but these are less understood. We conducted an experiment to determine whether an object's velocity affects which source is most effective for perceiving time to contact.

Binocular Perception of 2D Lateral Motion and Guidance of Coordinated Motor Behavior.

Zannoli, Cass, Alais, and Mamassian (2012) found greater audiovisual lag between a tone and disparity-defined stimuli moving laterally (90-170 ms) than for disparity-defined stimuli moving in depth or luminance-defined stimuli moving laterally or in depth (50-60 ms). We tested if this increased lag presents an impediment to visually guided coordination with laterally moving objects. Participants used a joystick to move a virtual object in several constant relative phases with a laterally oscillating stimulus.

Eye and hand movement strategies in older adults during a complex reaching task.

The kinematics of upper limb movements and the coordination of eye and hand movements are affected by ageing. These age differences are exacerbated when task difficulty is increased, but the exact nature of these differences remains to be established. We examined the performance of 12 older adults (mean age = 74) and 11 younger adults (mean age = 20) on a multi-phase prehension task.

Training to improve manual control in 7-8 and 10-12 year old children: Training eliminates performance differences between ages.

Many children have difficulty producing movements well enough to improve in perceptuo-motor learning. We have developed a training method that supports active movement generation to allow improvement in a 3D tracing task requiring good compliance control. We previously tested 7-8 year old children who exhibited poor performance and performance differences before training.

Information and control strategy to solve the degrees-of-freedom problem for nested locomotion-to-reach.

Locomoting-to-reach to a target is a common visuomotor approach behavior that consists of two nested component actions: locomotion and reaching. The information and control strategies that guide locomotion and reaching in isolation are well studied, but their interaction during locomoting-to-reach behavior has received little attention. We investigated the role of proportional rate control in unifying these components into one action.

A geometric and dynamic affordance model of reaches-to-grasp: Men take greater risks than women.

Mon-Williams and Bingham (2011) developed an affordance model of the spatial structure of reaches-to-grasp. With a single free parameter (P), the model predicted the safety margins (SMs) exhibited in maximum grasp apertures (MGAs), during the approach of a hand to a target object, as a function of an affordance measure of object size and a functional measure of hand size. An affordance analysis revealed that object size is determined by a diagonal through the object, called the maximum object extent.

The 50s cliff: perceptuo-motor learning rates across the lifespan.

We recently found that older adults show reduced learning rates when learning a new pattern of coordinated rhythmic movement. The purpose of this study was to extend that finding by examining the performance of all ages across the lifespan from the 20 s through to the 80 s to determine how learning rates change with age. We tested whether adults could learn to produce a novel coordinated rhythmic movement (90° relative phase) in a visually guided unimanual task.

Static and dynamic visual information about the size and passability of an aperture.

The role of static eyeheight-scaled information in perceiving the passability of and guiding locomotion through apertures is well established. However, eyeheight-scaled information is not the only source of visual information about size and passability. In this study we tested the sufficiency of two other sources of information, both of which are available only to moving observers (ie are dynamic) and specify aperture size in intrinsic body-scaled units.