认知发展的新兴观点，来源于西格勒，原文搬过来是：
One theory that does focus primarily on children's learning is the overlapping waves theory (Siegler,1996). This theory is based on three assumptions:
(1) children typically use a variety of strategies andways of thinking, rather than just a single one, to solve a given problem;
(2) the diverse strategies and ways of thinking coexist over prolonged periods of time,
not just during brief transition periods;
(3) experience brings changes in relative reliance on existing strategies and ways of thinking, as well as introduction of more advanced approaches.
儿童在问题解决时，往往采用多种策略。尽管这些策略有优劣之分，但是好的策略并不会覆盖掉原有的陈旧的策略。新策略的产生依赖于经验。
我只对（2）做出解释，在计算29+4时，数数策略是没有直接提取策略快的，但是儿童在解决这个问题时，往往一个一个数得到，喊出30掰1个手指，到31掰2个手指，到32掰3个手指，到33掰4个手指，4个了，喊了33，所以29+4=33。熟练的儿童可以在心理上建构29+4的竖式直接说出33。注意这个挨个儿数的低级策略在成年人中几乎不用的，但是你有时依然会依赖它来解决问题，问你10.29号过4天是几号，你就将激活数数策略，你会想出日历或看着日历，喊出10.30掰1个手指，10.31掰2个手指，11.1掰3个手指，11.2掰4个，所以过了4天是11月2日。