No abstract

A common perception-action learning task is to teach participants to produce a novel coordinated rhythmic movement, e.g. 90 degrees mean relative phase. As a general rule, people cannot produce these novel movements stably without training. This is because they are extremely poor at discriminating the perceptual information required to coordinate and control the movement, which means people require additional (augmented) feedback to learn the novel task. Extant methods (e.g. visual metronomes, Lissajous figures) work, but all involve transforming the perceptual information about the task and thus altering the perception-action task dynamic being studied. We describe and test a new method for providing online augmented coordination feedback using a neutral colour cue. This does not alter the perceptual information or the overall task dynamic, and an experiment confirms that (a) feedback is required for learning a novel coordination and (b) the new feedback method provides the necessary assistance. This task-appropriate augmented feedback therefore allows us to study the process of learning while preserving the perceptual information that constitutes a key part of the task dynamic being studied. This method is inspired by and supports a fully perception-action approach to coordinated rhythmic movement.

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. We determined learning rates to quantify changes in learning with age and to determine at what ages the changes occur. We found, as before, that learning rates of participants in their 70 s and 80 s were half those of participants in their 20 s. We also found a gradual slow decline in learning rate with age until approximately age 50, when there was a sudden drop to a reduced learning rate for the 60 though 80 year olds. We discuss possible causes for the “50 s cliff” in perceptuo-motor learning rates and suggest that age related deficits in perception of complex motions may be the key to understanding this result.

Feedback is a central feature of neural systems and of crucial importance to human behaviour as shown in goal directed actions such as reaching-to-grasp. One important source of feedback in reach-to-grasp behaviour arises from the haptic information obtained after grasping an object. We manipulated the felt distance and/or size of a visually constant object to explore the role of haptic information in the calibration of reaching and grasping. Crucially, our design explored post-adaptation effects rather than the previously documented role of haptic information in movement organisation. A post-adaptation reach-to-grasp task showed: (1) distorted haptic feedback caused recalibration; (2) reach distance and grasp size could be calibrated separately but, if calibrated simultaneously, then (3) recalibration was greater when distance and size changed in a consistent (e.g. reaching for a larger object at a greater distance) rather than an inconsistent (e.g. a smaller object at a greater distance) fashion. These interactions reveal the integral nature of reach-to-grasp organization, that is, that reaching and grasping are integrated components of a single action system.

There is an ongoing debate as to whether a greater degree of sensory-motor control is required to maintain skills as humans progress to be septuagenarians. Here, we investigate the dependence of older participants upon vision to execute skilled prehension movements. In a first experiment, participants were required to place a small, round peg in one of three randomly cued holes. A mirror apparatus was used to create conditions where they could always see the target locations, but vision of their hand approaching the target could be removed, and we explored end position accuracy. In a second experiment, we examined the ability of participants to precisely control their grasp action under conditions where they could see the objects but not their hands completing the action. The results showed that in Experiment 1, the older adults undershot the target in their primary submovement and hence had to move further in their secondary movement to achieve their goal. In Experiment 2, the older adults spent longer in the final adjustment phase (a near zero velocity phase at the end of the reach) when vision of the hand was unavailable. These findings suggest that older adults are indeed more reliant on visual feedback than the young in tasks that require precise manual control, and this clarifies conflicting accounts in the prior literature.

This study examined perception-action learning in younger adults in their 20s compared to older adults in their 70s and 80s. The goal was to provide, for the first time, quantitative estimates of perceptuo-motor learning rates for each age group and to reveal how these learning rates change between these age groups. We used a visual coordination task in which participants are asked to learn to produce a novel-coordinated rhythmic movement. The task has been studied extensively in young adults, and the characteristics of the task are well understood. All groups showed improvement, although learning rates for those in their 70s and 80s were half the rate for those in their 20s. We consider the potential causes of these differences in learning rates by examining performance across the different coordination patterns examined as well as recent results that reveal age-related deficits in motion perception.

Bingham and Pagano (1998) argued that metric space perception should be investigated using relevant action measures because calibration is an intrinsic component of perception/action that yields accurate targeted actions. They described calibration as a mapping from embodied units of perception to embodied units of action. This mapping theory yields a number of predictions. We tested two of them. The first prediction is that calibration should be action specific because what is calibrated is a mapping from perceptual units to a unit of action. Thus, calibration does not generalize to other actions.This prediction is consistent with the 'action specificity approach' to calibration (Proffitt, 2008). The second prediction is that a change in perceptual units should generalize to all relevant actions that are guided using that perceptual information. The same perceptual units can be mapped to different actions.Change in the unit affects all relevant actions. This prediction is consistent with the 'general purpose perception approach' (Loomis & Philbeck, 2008). In Experiment 1, two targeted actions, throwing and extended reaching were tested to determine if they were comparable in precision and in response to distorted calibration. They were. Comparing these actions, the first prediction was tested in Experiment 2 and confirmed. The second prediction was tested in Experiment 3 and confirmed. The 'action specificity' and 'general purpose perception' approaches each fail to predict the alternative results predicted by the other. Both sets of results were predicted by the 'mapping among embodied units' theory of calibration.

Bingham and Pagano (1998) argued that calibration is an intrinsic component of perception-action that yields accurate targeted actions. They described calibration as of a mapping from embodied units of perception to embodied units of action. This mapping theory yields a number of predictions. The authors tested 2 of them. The 1st prediction is that change in the size of perceptual units should yield a corresponding change in the slope of the relation between response distances and actual target distances. In Experiment 1, the authors tested this prediction by manipulating interpupillary distance (IPD) as the unit for binocular perception of distance using vergence angles. In Experiment 2, they manipulated eye height (EH) as the unit for monocular perception of distance using elevation angles. In both cases, the results confirmed the predictions. The 2nd prediction was that perceptual units should interact to cross calibrate one another according to a dominance hierarchy among the units. The theory predicts a more temporally stable unit is used to calibrate a less stable unit but not the reverse. EH units change frequently, but IPD units do not, so IPD should be dominant. Simultaneously available IPD and EH units were perturbed successively (without feedback). As predicted, EH was recalibrated by IPD, but IPD was not recalibrated by EH. The mapping among units theory of calibration was thus supported.