Thelen E, Corbetta D, Spencer J P
Department of Psychology, Indiana University, Bloomington 47405, USA.
J Exp Psychol Hum Percept Perform. 1996 Oct;22(5):1059-76. doi: 10.1037//0096-1523.22.5.1059.
When infants first learn to reach at about 4 months, their hand paths are jerky and tortuous, but their reaches become smoother and straighter over the first year. Here the authors consider the role of the underlying limb dynamics, which scale with movement speed, on the development of trajectory control. The authors observed 4 infants weekly and then biweekly from reach onset to 1 year. Improvements in trajectories were not linear, but showed plateaus and regressions in straightness and smoothness. When infants' nonreaching movements were fast, their reaches were also fast, and faster reaches were also less straight. This is consistent with an equilibrium trajectory form of control, where development involves the increasing ability to stabilize the trajectory against self-generated movement perturbations.
婴儿在大约4个月大时首次学会伸手够物，此时他们的手部动作轨迹是急促且曲折的，但在第一年中，他们的伸手动作会变得更加平稳和笔直。在此，作者探讨了与运动速度相关的肢体动力学在轨迹控制发展过程中所起的作用。作者对4名婴儿从开始伸手够物到1岁期间进行了每周一次、之后每两周一次的观察。轨迹的改善并非呈线性，而是在直线度和平滑度上出现了平稳期和倒退期。当婴儿的非伸手动作较快时，他们的伸手动作也较快，而且较快的伸手动作直线度也较低。这与一种平衡轨迹控制形式相符，即发展涉及到增强抵抗自身产生的运动干扰来稳定轨迹的能力。
