A Note on the Conscious Controls of Motor Units by Children Under Six

A simple form of training the conscious control of motor units in skeletal muscle has been demonstrated in a series of children under age 6. Easy boredom is the chief deterrent in the very young. So long as a child understands and cooperates, he can learn to isolate single units in a period of about 30 min.     

The Visuomotor System Resists the Horizontal-Vertical Illusion

The effect of the horizontal-vertical illusion on the visual and visuomotor systems was investigated. Participants (N = 8) viewed horizontal and vertical lines in an inverted-T stimulus and judged whether the two line segments were the same or different lengths. Participants also reached out and grasped either the vertical or the horizontal line segment of the stimulus. Perceptually, participants succumbed to the illusion; that is, they judged Ts of equal horizontal and vertical line lengths to be different and Ts of unequal line lengths to be the same. When reaching toward the same stimuli, however, the size of their grip aperture was scaled appropriately for the various line lengths. Thus, whereas the perceptual system succumbed to the illusion, the visuomotor system did not. Those results support a model proposed by M. A. Goodale and A. D. Milner (1992), who posited separate cortical pathways for visual perception and visually guided action.     

Changes in Limb Stiffness Under Conditions of Mental Stress

In 2 experiments, the effects of mental stress on limb stiffness were investigated. The relative contribution to arm stiffness of individual muscle activity, co-contraction, muscle reflexes, and postural adjustments were examined. In each experiment, participants (N = 24, Experiment 1; N = 16, Experiment 2) held their supinated hand under a tray that they were required to return to horizontal after it had been suddenly released. Electromyographic activity in the biceps and triceps muscles was recorded, as were elbow and wrist angles and tray displacement. In Experiment 1, mental arithmetic stress was shown to lead to decreased tray displacement (i.e., increased resistance) compared with displacements under the control, unstressed condition, as well as to increased elbow flexion before tray release. In Experiment 2, the increased resistance to perturbation caused by mental stress was found to be independent of initial elbow angle, but to vary as a function of the amount of upward force exerted before tray release. The authors conclude that stress-induced increases in limb stiffness result from changes in the initial position of the elbow, specified by its angle, together with the initial force exerted by participants to counteract the mechanical perturbations.     

Effect of Practice on Effector Independence

The authors' primary purpose in the present experiment was to determine if practice changes the extent to which simple motor sequences are effector independent. Contralateral and ipsilateral effector transfers were assessed in 24 participants after 1 (200 trials) and 4 (800 trials) days of practice. The response sequence became increasingly effector dependent; the response structure and the scaling of force on the effector transfer tests were no better after 4 days of practice than after only 1 day, even though retention performance improved substantially. Those results are consistent with the notion that participants refine their movements over extended practice by exploiting the unique characteristics of the effectors. The additional practice results in a more effective movement when the same effectors are used but is of little value when different effectors are required.     

The Large Pursuit Rotor

The question of whether certain phenomena that occur on the conventional rotary pursuit and other small apparatus also appear on a gross motor task was examined using a large pursuit rotor that required whole-body movements. College males (n=29) were given 90 10-sec trials over three consecutive days with 30 trials of continuous practice per day. The existence of reactive inhibition, reminiscence, and warmup decrement was confirmed, indicating that common mechanisms underlie both fine and gross bodily movements. In addition, the substantial amounts of learning and the high reliabilities for performance and learning indicated that the present apparatus has considerable potential for motor-learning research.     

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.     

Young children’s analogical problem solving: Gaining insights from video displays

This study examined how toddlers gain insights from source video displays and use the insights to solve analogous problems. The sample of 2- and 2.5-year-olds viewed a source video illustrating a problem-solving strategy and then attempted to solve analogous problems. Older, but not younger, toddlers extracted the problem-solving strategy depicted in the video and spontaneously transferred the strategy to solve isomorphic problems. Transfer by analogy from the video was evident only when the video illustrated the complete problem goal structure, including the character’s intention and the action needed to achieve a goal. The same action isolated from the problem-solving context did not serve as an effective source analogue. These results illuminate the development of early representation and processes involved in analogical problem solving. Theoretical and educational implications are discussed.     

Motor Response Variations: Peripheral and Central Sources of Error

The purpose of this research was to test the hypothesis that the relative involvement of peripheral versus central nervous system activity during response variations determines the locus of error production in a subsequent criterion response. The hypothesis was tested by comparing ipsilateral and contralateral transfer of a criterion response following response variations that emphasized proportionately different involvement of the peripheral and central systems. When subjects were provided with knowledge of results (KR) to maintain a 30% maximum voluntary contraction (MVC), ipsilateral but not contralateral bias errors occurred on a subsequent dynamic response. When subjects maintained a 30% MVC without KR, however, subsequent ipsilateral bias errors were greater than contralateral bias errors. Finally, when subjects imaged a 30% MVC, subsequent bias errors were equivalent across limbs. These results are interpreted as support for the hypothesis.     

尝试提取复杂信息失败的学习：吃一堑长一智？

摘 要：在学习中,提取失败能否产生对知识的有效学习是一个很有意义的研究课题。以事实和概念类知识为实验材料,三个实验采用经典范式探讨了复杂意义条件下的提取失败后的学习效果。结果显示仅在尝试提取事实类题目失败后,促进了知识的保持和迁移;在迁移成绩上延时反馈优于即时反馈的效果。表明尝试提取复杂材料的信息失败后,知识的类型和反馈的时机决定了学习效果。     

Reductive and Emergent Views on Motor Learning in Rehabilitation Practice

To allow different views on motor learning to inform rehabilitation research, the authors aimed to explicate a frequently missed yet fundamental difference in starting point of such views. By considering how rehabilitation in practice answers the question of what parts an activity consists of, reductive and emergent approaches to motor learning are identified and traced throughout rehabilitation practice. The authors show that when a task is cut up along reductive dimensions while also apparently relying on emergent components, this unequally favors the reductive approach and acts to limit the views on motor learning available. By showing the approaches in practice, the authors hope to inspire an awareness that brings both approaches the opportunity to independently inform research so that new theories and practices can proliferate.