Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; The Center for Science and Society, Columbia University, New York, NY 10027, USA.
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Curr Biol. 2017 Feb 6;27(3):359-370. doi: 10.1016/j.cub.2016.12.031. Epub 2017 Jan 5.
Probability distributions over external states (priors) are essential to the interpretation of sensory signals. Priors for cultural artifacts such as music and language remain largely uncharacterized, but likely constrain cultural transmission, because only those signals with high probability under the prior can be reliably reproduced and communicated. We developed a method to estimate priors for simple rhythms via iterated reproduction of random temporal sequences. Listeners were asked to reproduce random "seed" rhythms; their reproductions were fed back as the stimulus and over time became dominated by internal biases, such that the prior could be estimated by applying the procedure multiple times. We validated that the measured prior was consistent across the modality of reproduction and that it correctly predicted perceptual discrimination. We then measured listeners' priors over the entire space of two- and three-interval rhythms. Priors in US participants showed peaks at rhythms with simple integer ratios and were similar for musicians and non-musicians. An analogous procedure produced qualitatively different results for spoken phrases, indicating some specificity to music. Priors measured in members of a native Amazonian society were distinct from those in US participants but also featured integer ratio peaks. The results do not preclude biological constraints favoring integer ratios, but they suggest that priors on musical rhythm are substantially modulated by experience and may simply reflect the empirical distribution of rhythm that listeners encounter. The proposed method can efficiently map out a high-resolution view of biases that shape transmission and stability of simple reproducible patterns within a culture.
外部状态（先验）的概率分布对于解释感官信号至关重要。文化人工制品（如音乐和语言）的先验仍然在很大程度上没有得到描述，但它们可能会限制文化传播，因为只有那些在先验下具有高概率的信号才能被可靠地复制和传播。我们开发了一种通过迭代复制随机时间序列来估计简单节奏先验的方法。要求听众复制随机的“种子”节奏；他们的复制作为刺激被反馈回来，随着时间的推移，内部偏见开始占主导地位，因此可以通过多次应用该程序来估计先验。我们验证了所测量的先验在复制模态上是一致的，并且它正确地预测了感知辨别力。然后，我们测量了听众在两个和三个区间节奏的整个空间中的先验。美国参与者的先验在具有简单整数比的节奏上出现峰值，并且音乐家和非音乐家的先验相似。类似的程序对于口语短语产生了定性不同的结果，表明音乐具有一些特异性。来自一个本土亚马逊社会的成员的先验与美国参与者的不同，但也具有整数比峰值。结果并不排除有利于整数比的生物学限制，但它们表明音乐节奏的先验在很大程度上受到经验的调节，并且可能仅仅反映了听众遇到的节奏的经验分布。所提出的方法可以有效地描绘出在一种文化中塑造简单可重复模式的传输和稳定性的偏见的高分辨率视图。
