The relative contribution of demographic versus cultural diffusion to the evolution of Han Chinese dialects has been unclear. By digitizing a large lexical dataset of Chinese dialects and comparing it to genetic profiles, Yang et al. reveal a hybrid model of language diffusion that consists of both population migrations and social learning across different regions of China.

See Yang et al. See also News & Views by Xu & Wang

Is know-how copying a uniquely human capacity? Van Leeuwen and colleagues demonstrate that chimpanzees use social learning to acquire a skill that they failed to innovate, which suggests that chimpanzees — like humans — use know-how copying to expand their skill set.

See Van Leeuwen et al.

In 2021, the USA provided an unconditional child allowance to most families with children. Using anonymized mobile-location as well as debit and credit card data, Parolin et al. find that the allowance increased spending at childcare centres, health- and personal-care establishments, and grocery stores. On the other hand, there was no evidence that the allowance increased tobacco or alcohol purchases.

See Parolin et al.

How much sleep is necessary for optimal cognitive function and brain health? Human sleep deprivation experiments in the laboratory, observational studies and the behavioural ecology and evolution literature provide different answers to this question. Fjell and Walhovd adopt a transdisciplinary view of the evidence and argue that individual sleep need is highly flexible and affected by environmental factors, individual needs and motivation. This flexibility and broader context are frequently overlooked in laboratory-based sleep restriction studies and in sleep recommendations, but are important to take into account for a more ecologically valid view of human sleep needs.

See Fjell and Walhovd

Recent research has shown that people can perceive the shape of objects, even when the objects are not directly perceptible (for instance, when draped in cloth). These findings present a challenge to existing theories of shape perception, which are based on the use of surface cues alone. Yildirim et al. present a computational model of three-dimensional shape perception that integrates intuitive physics and analysis-by-synthesis to explain how shape can be inferred both when surface object cues are available and when they are not (as in cloth draping).

See Yildirim et al.

How does the mind bootstrap its way to complex concepts? Across four experiments, Zhao et al. show that a key feature of the acquisition of complex concepts is the incremental construction of compositional representations. The authors then develop a model of conceptual bootstrapping, which captures the process of learning complex concepts by recursively combining simpler concepts.

See Zhao et al.