Agam Yigal, Galperin Henry, Gold Brian J, Sekuler Robert
Volen Center for Complex Systems, Brandeis University, Waltham, MA, USA.
J Vis. 2007 Mar 19;7(5):1.1-17. doi: 10.1167/7.5.1.
Many imitative behaviors entail complex sequences of component actions that must be recalled and performed in the proper order. It is well known that imitation of complex actions tends to improve with repeated opportunities to observe and execute the target behavior. But what actually makes this practice-based improvement possible? To address this question, we had subjects view and then reproduce sequences of connected, randomly directed motions of a disc. Even a single repetition of a motion sequence substantially reduced errors in reproduction. Improvement seemed to follow a power law, with accuracy in reproducing each motion segment improving by an amount proportional to the current error for that segment. Analysis of the pauses separating a reproduction's segments suggests that with learning, multiple segments in memory are grouped into more compact representations. To test overt performance's contribution to repetition-based improvement, we compared subjects' performance when they reproduced the stimulus trajectory after each repetition to when they did so only once, after the final repetition. Performance was similar following the final repetition in both conditions, indicating that seeing the model, without actual imitation, was sufficient for learning--even in the absence of an explicit error signal. In another experiment, subjects viewed three presentations of each model, with the second presentation given in forward (start to end) or backward (end to start) order. Performance was significantly better when all three presentations were in the same, consistent order, suggesting that repetition reinforced some temporal aspects of a trajectory as it was being learned, and not merely a better representation of the static shape traced by the motion of the disc. These results provide a first look into explicit learning of sequential, nonverbal material, which is central to many tasks of daily life.
许多模仿行为需要一系列复杂的组成动作，这些动作必须按正确顺序被回忆并执行。众所周知，对复杂动作的模仿往往会随着观察和执行目标行为的机会增多而得到改善。但究竟是什么使得这种基于练习的改善成为可能呢？为了解决这个问题，我们让受试者观看并随后重现圆盘的一系列相互连接、随机指向的运动。即使是对运动序列进行单次重复，也能大幅减少重现中的错误。改善似乎遵循幂律，即重现每个运动片段的准确性提高的幅度与该片段当前的误差成比例。对分隔重现片段的停顿进行分析表明，随着学习的进行，记忆中的多个片段会被组合成更紧凑的表征。为了测试公开表现对基于重复的改善的贡献，我们比较了受试者在每次重复后重现刺激轨迹时的表现，以及他们在最后一次重复后只重现一次时的表现。在两种情况下，最后一次重复后的表现相似，这表明即使没有实际模仿，仅仅看到模型就足以学习——即使没有明确的错误信号。在另一个实验中，受试者观看每个模型的三次展示，第二次展示按正向（从开始到结束）或反向（从结束到开始）顺序进行。当所有三次展示的顺序相同时，表现明显更好，这表明重复在学习轨迹时强化了轨迹的一些时间方面，而不仅仅是对圆盘运动所描绘的静态形状的更好表征。这些结果首次揭示了对顺序性非语言材料的显性学习，而这在许多日常生活任务中至关重要。
