Comprehension and production of non-canonical word orders in Mandarin-speaking child heritage speakers

Across languages, structures with non-canonical word order have been shown to be problematic for both child and adult heritage speakers. To investigate the linguistic and child-level factors that modulate heritage speakers’ difficulties with non-canonical word orders, we examined the comprehension and production of three Mandarin non-canonical structures in 5- to 9-year-old Mandarin-English heritage children and compared them to age-matched Mandarin-speaking monolingual children and adults. Specifically, we examined how linguistic properties, such as linear word order, presence or absence of morphosyntactic cues, and surface structural overlap between languages, as well as child-level factors, such as chronological age and current home language use affect the acquisition of non-canonical structures in heritage children and their monolingual peers. Results showed that although heritage children could use morphosyntactic cues, they did not show monolingual-level sensitivity to passive-related morphology. Additionally, children produced more canonical SVO word order, which is shared between English and Mandarin, and preferred the reverse interpretations of non-canonical structures in comprehension. These responses were taken as evidence for cross-linguistic influence from the majority to the minority language. Finally, although non-canonical structures caused difficulties for child heritage speakers, their performance was modulated by structure and improved with age, over and above heritage language use.

A tale of winglets: evolution of flight morphology in stick insects

The evolutionary transition between winglessness and a full-winged morphology requires selective advantage for intermediate forms. Conversely, repeated secondary wing reductions among the pterygotes indicates relaxation of such selection. However, evolutionary trajectories of such transitions are not well characterized. The stick insects (Phasmatodea) exhibit diverse wing sizes at both interspecific and intersexual levels, and thus provide a system for examining how selection on flight capability, along with other selective forces, drives the evolution of flight-related morphology. Here, we examine variation in relevant morphology for stick insects using data from 1100+ individuals representing 765 species. Although wing size varies along a continuous spectrum, taxa with either long or miniaturized wings are the most common, whereas those with intermediate-sized wings are relatively rare. In a morphological space defined by wing and body size, the aerodynamically relevant parameter termed wing loading (the average pressure exerted on the air by the wings) varies according to sex-specific scaling laws; volant but also flightless forms are the most common outcomes in both sexes. Using phylogenetically-informed analyses, we show that relative wing size and body size are inversely correlated in long-winged insects regardless of sexual differences in morphology and ecology. These results demonstrate the diversity of flight-related morphology in stick insects, and also provide a general framework for addressing evolutionary coupling between wing and body dimensions. We also find indirect evidence for a ‘fitness valley’ associated with intermediate-sized wings, suggesting relatively rapid evolutionary transitions between wingless and volant forms.