Young children fail to generate an additive ratchet effect in an open-ended construction task

The ratchet effect–the gradual accumulation of changes within a cultural trait beyond a level that individuals can achieve on their own–arguably rests on two key cognitive abilities: high-fidelity social learning and innovation. Researchers have started to simulate the ratchet effect in the laboratory to identify its underlying social learning mechanisms, but studies on the developmental origins of the ratchet effect remain sparse. We used the transmission chain method and a tower construction task that had previously been used with adults to investigate whether “generations” of children between 4 and 6 years were able to make a technological product that individual children could not yet achieve. 21 children in a baseline and 80 children in transmission chains (each consisting of 10 successive children) were asked to build something as tall as possible from plasticine and sticks. Children in the chains were presented with the constructions of the two preceding generations (endstate demonstration). Results showed that tower heights did not increase across the chains nor were they different from the height of baseline towers, demonstrating a lack of improvement in tower height. However, we found evidence for cultural lineages, i.e., construction styles: towers within chains were more similar to each other than to towers from different chains. Possible explanations for the findings and directions for future research are suggested.

棘轮效应（ratchet effect）指文化特质逐步积累至个体无法独自达成的水平的现象，其形成核心依赖两项关键认知能力：高保真社会学习与创新。目前已有研究者开始在实验室中模拟棘轮效应，以探明其背后的社会学习机制，但针对棘轮效应发展起源的相关研究仍较为匮乏。
本研究采用过往针对成人群体开发的传递链方法（transmission chain method）与搭塔任务（tower construction task），探究4至6岁儿童的各代参与者能否搭建出个体儿童尚无法独立完成的技术产物。研究共招募21名儿童参与基线组，80名儿童被分为8条传递链，每条传递链包含10名连续参与的儿童，所有儿童均被要求利用橡皮泥与木棍搭建尽可能高的结构。传递链组的儿童会观看到前两代参与者的搭建终态成品（终态演示）。
实验结果显示，传递链各组的搭塔高度未随代次递增，且与基线组搭塔高度无显著差异，表明搭塔高度未出现提升。不过，研究发现了文化谱系（cultural lineages）层面的证据：同一传递链内的搭塔结构相似度显著高于不同传递链间的搭塔结构，即存在特定的搭建风格。
本研究针对上述实验结果提出了可能的解释方向，并为未来研究指明了可行路径。