Animals’ cognitive abilities can be tested by allowing them to choose between alternatives, with only one alternative offering the correct solution to a novel problem. Hermit crabs are evolutionarily specialized to navigate while carrying a shell, with alternative shells representing different forms of ‘extended architecture’, which effectively change the extent of physical space an individual occupies in the world. It is unknown whether individuals can choose such architecture to solve novel navigational problems. Here, we designed an experiment in which social hermit crabs (Coenobita compressus) had to choose between two alternative shells to solve a novel problem: escaping solitary confinement. Using X-ray microtomography and 3D-printing, we copied preferred shell types and then made artificial alterations to their inner or outer shell architecture, designing only some shells to have the correct architectural fit for escaping the opening of an isolated crab’s enclosure. In our ‘escape artist’ experimental design, crabs had to choose an otherwise less preferred shell, since only this shell had the right external architecture to allow the crab to free itself from isolation. Across multiple experiments, crabs were willing to forgo preferred shells and choose less preferred shells that enabled them to escape, suggesting these animals can solve novel navigational problems with extended architecture. Yet, it remains unclear if individuals solved this problem through trial-and-error or were aware of the deeper connection between escape and exterior shell architecture. Our experiments offer a foundation for further explorations of physical, social, and spatial cognition within the context of extended architecture.

可以通过允许动物在其他选择之间进行选择来测试动物的认知能力，只有一种选择可以为新问题提供正确的解决方案。寄居蟹在携带贝壳的过程中经过专门进化，可以替代贝壳代表不同形式的“扩展建筑”，从而有效地改变了个人在世界上所占据的物理空间。人们是否可以选择这种架构来解决新颖的导航问题还不得而知。在这里，我们设计了一个实验，其中社会寄居蟹（Coenobita compressus）必须在两个替代壳之间进行选择，以解决一个新问题：逃避单独禁闭。我们使用X射线显微断层照相术和3D打印技术，复制了首选的贝壳类型，然后对其内壳或外壳结构进行了人工更改，仅设计了一些壳以具有正确的结构适合性，以逃避孤立的蟹壳的开口。在我们的“逃脱艺术家”实验设计中，螃蟹不得不选择一种原本不那么受欢迎的贝壳，因为只有这种贝壳具有正确的外部结构，才能使螃蟹摆脱孤立。在多个实验中，螃蟹愿意放弃首选的贝壳，而选择不太喜欢的贝壳使它们逃脱，这表明这些动物可以通过扩展的结构解决新的航行问题。然而，目前尚不清楚是个人通过反复试验解决了这个问题，还是意识到逃生与外壳结构之间的深层联系。我们的实验为在扩展架构的背景下进一步探索物理，社会和空间认知奠定了基础。