Unweighting infants reveals hidden motor skills

We investigated the role of rate limiting factors in development using walking as a model system. The achievement of bipedal posture and locomotion are among the most significant achievements in an infant's first year, with poor balance and weak muscles long proposed as the rate limiting factors. Compensating for either may reveal upright motor skill that has not yet emerged in the infant's natural repertoire. To probe this question, we unweighted prewalking infants and measured their performance in various standing and walking behaviors while unweighted compared to baseline. Our secondary objective was to determine if the influence of unweighting was related to infants’ locomotor experience. Infants stood unsupported for longer durations with 20% or 40% unweighting. Infants took more independent steps and more steps with one hand held with 40% unweighting. No differences in transition to/from standing were observed. Locomotor experience was related to the influence of unweighting during cruising and walking with a push toy. This is the first report of more advanced motor skills—longer periods of unsupported standing and the emergence of independent walking—revealed by unweighting infants. We interpret our observations to suggest that the refinement of motor control needed to support bipedal posture and locomotion precedes the functional emergence of these skills in infants. In other words, the musculoskeletal components required for walking are slower to develop than the neurological factors – and consequently may be the rate limiters. We further suggest that training regimens including unweighting should be explored in infants with motor delays.     

Overmatching in rats: the barrier choice paradigm

The barrier choice paradigm was used to impose a cost on rats' behavior of traveling between two levers: Pressing on two levers was reinforced with food on concurrent random-interval schedules, but rats had to climb over a barrier to move from one lever to another. The height of the barrier separating the levers was increased from 30.5 to 45.7 cm across two phases that involved various pairs of random-interval schedules. With the 30.5-cm barrier, the generalized matching law showed slopes equal to or slightly above 1.0 for response and time allocation. With the 45.7-cm barrier, the generalized matching law showed slopes above 1.2 for responses, indicating that sensitivity to reinforcement increased with increasing barrier height. For time allocation the slopes remained close to 1.0; sensitivity to reinforcement did not seem to increase with increasing barrier height. The role of locomotion effort in choice situations is discussed.     

The good of boredom

I argue that the state of boredom (i.e., the transitory and non-pathological experience of boredom) should be understood to be a regulatory psychological state that has the capacity to promote our well-being by contributing to personal growth and to the construction (or reconstruction) of a meaningful life.     

Distraction Affects the Performance of Obstacle Avoidance During Walking

In this study, dual-task interference in obstacle-avoidance tasks during human walking was examined. Ten healthy young adults participated in the experiment. While they were walking on a treadmill, an obstacle suddenly fell on the treadmill in front of their left leg during either midswing, early stance, or late stance of the ipsilateral leg. Participants were instructed to avoid the obstacle, both as a single task and while they were concurrently performing a cognitive secondary task (dual task). Rates of failure, avoidance strategy, and a number of kinematic parameters were studied under both task conditions. When only a short response time was available, rates of failure on the avoidance task were larger during the dual task than during the single task. Smaller crossing swing velocities were found during the dual task as compared with those observed in the single task. The difference in crossing swing velocities was attributable to increased stiffness of the crossing swing limb. The results of the present study indicated that divided attention affects young and healthy individuals' obstacle-avoidance performance during walking.     

Boundary Distance Effects on Overshooting

Experiments with a subject-paced pursuit tracking task show that overshoot rate is dependent upon the distance between the target and the display boundary measured in the direction of movement, and that a previously noted inverse relationship with distance to the target is artifactual. The effect held for tasks with direct and reverse control-display relations, and for tasks with constant and variable target distances. The findings were consistent with Wetford’s (1968) hypothesis that a pursuit response is initiated with a ballistic, distance-covering, movement. Ralph Leonardo carried out extensive work in collecting data, Fred Hyde maintained the apparatus, and Georgie Green assisted in data analysis.     

Mathematical Models of Central Pattern Generators in Locomotion

Possible neural connective patterns and functions with respect to interlimb coordination are studied theoretically with a mathematical model of the central pattern generating system for cat locomotion. Activities in populations of neurons controlling limb joint flexors and extensors in all four limbs are represented by a system of nonlinear differential equations. Solutions of the system for various parameter values simulate various gaits of the cat. The model is shown to be capable of generating all gaits of the cat and accounting for corresponding phase changes in interlimb coordination. The model also exhibits smooth changes of gait, and smooth initiation and termination of stepping. Further, within each limb, muscle sequencing, step cycle phases, and flexor-extensor interactions can be studied. The model suggests that one of the simplest mechanisms for a central command system to change the gait is via inhibition of specific interlimb propriospinal pathways. In a final section, properties of both proposed single limb and interlimb models are reviewed with specific reference to planning future experimental and theoretical studies.     

Is the Critical Point for Aperture Crossing Adapted to the Person-Plus-Object System?

When passing through apertures, individuals scale their actions to their shoulder width and rotate their shoulders or avoid apertures that are deemed too small for straight passage. Carrying objects wider than the body produces a person-plus-object system that individuals must account for in order to pass through apertures safely. The present study aimed to determine whether individuals scale their critical point to the widest horizontal dimension (shoulder or object width). Two responses emerged: Fast adapters adapted to the person-plus-object system by maintaining a consistent critical point regardless of whether the object was carried while slow adapters initially increased their critical point (overestimated) before adapting back to their original critical point. The results suggest that individuals can account for increases in body width by scaling actions to the size of the object width but people adapt at different rates.     

Choosing the shortest way to Mum: auditory guided rotation in 6- to 9-month-old infants

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. Behavior 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 behavior in the environment.     

儿童早期的动作发展对认知发展的作用

早期儿童与环境的相互作用通过动作来完成。儿童在与环境的相互作用过程中动作得到发展,与此同时也促进了认知发展。该文主要介绍了国内外的一些研究成果,阐述了爬行和手部动作对儿童认知发展的作用。发现儿童早期动作的发展是认知发展的外在表现,同时早期动作的发展也将促使儿童的认知发展不断高级化、复杂化。儿童通过爬行获得了运动经验,促进了感知觉的发展;而手部动作主要包括抓握动作和手势的发展,在儿童与环境的相互作用过程中则主要发挥着重要的中介作用。