Compositionality is an important explanatory target in emergent communication and language evolution. The vast majority of computational models of communication account for the emergence of only a very basic form of compositionality: trivial compositionality. A compositional protocol is trivially compositional if the meaning of a complex signal (e.g. blue circle) boils down to the intersection of meanings of its constituents (e.g. the intersection of the set of blue objects and the set of circles). A protocol is non-trivially compositional (NTC) if the meaning of a complex signal (e.g. biggest apple) is a more complex function of the meanings of their constituents. In this paper, we review several metrics of compositionality used in emergent communication and experimentally show that most of them fail to detect NTC - i.e. they treat non-trivial compositionality as a failure of compositionality. The one exception is tree reconstruction error, a metric motivated by formal accounts of compositionality. These results emphasise important limitations of emergent communication research that could hamper progress on modelling the emergence of NTC.

中文翻译：

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测量紧急通信中的非平凡组合性

组合性是紧急交流和语言进化的重要解释目标。绝大多数通信计算模型只说明了一种非常基本的组合形式的出现：平凡组合。如果复杂信号（例如蓝色圆圈）的含义归结为其成分的含义的交集（例如蓝色对象集和圆圈集的交集），则组合协议是平凡组合的。如果复杂信号（例如最大的苹果）的含义是其组成部分含义的更复杂函数，则协议是非平凡组合 (NTC)。在本文中，我们回顾了紧急通信中使用的几种组合性指标，并通过实验表明它们中的大多数都无法检测到 NTC——即 他们将非平凡的组合性视为组合性的失败。一个例外是树重建错误，这是一种由组合性的正式说明驱动的度量。这些结果强调了紧急通信研究的重要局限性，可能会阻碍 NTC 出现建模的进展。