Turn-taking in conversation is a cognitively demanding process that proceeds rapidly due to interlocutors utilizing a range of cues to aid prediction. In the present study we set out to test recent claims that content question words (also called wh-words) sound similar within languages as an adaptation to help listeners predict that a question is about to be asked. We test whether upcoming questions can be predicted based on the first phoneme of a turn and the prior context. We analyze the Switchboard corpus of English by means of a decision tree to test whether /w/ and /h/ are good statistical cues of upcoming questions in conversation. Based on the results, we perform a controlled experiment to test whether people really use these cues to recognize questions. In both studies we show that both the initial phoneme and the sequential context help predict questions. This contributes converging evidence that elements of languages adapt to pragmatic pressures applied during conversation.

Do all languages convey semantic knowledge in the same way?If language simply mirrors the structure of the world, theanswer should be a qualified “yes”. If, however, languagesimpose structure as much as reflecting it, then even ostensiblythe “same” word in different languages may mean quitedifferent things. We provide a first pass at a large-scalequantification of cross-linguistic semantic alignment ofapproximately 1000 meanings in 55 languages. We find thatthe translation equivalents in some domains (e.g., Time,Quantity, and Kinship) exhibit high alignment acrosslanguages while the structure of other domains (e.g., Politics,Food, Emotions, and Animals) exhibits substantial cross-linguistic variability. Our measure of semantic alignmentcorrelates with known phylogenetic distances betweenlanguages: more phylogenetically distant languages have lesssemantic alignment. We also find semantic alignment tocorrelate with cultural distances between societies speakingthe languages, suggesting a rich co-adaptation of language andculture even in domains of experience that appear mostconstrained by the natural world.

Languages combine arbitrary and iconic signals. How do iconic signals emerge and when do they persist? We present an experimental study of the role of iconicity in the emergence of structure in an artificial language. Using an iterated communication game in which we control the signalling medium as well as the meaning space, we study the evolution of communicative signals in transmission chains. This sheds light on how affordances of the communication medium shape and constrain the mappability and transmissibility of form-meaning pairs. We find that iconic signals can form the building blocks for wider compositional patterns.

Inorganic semiconductor nanocrystals interfaced with spin-triplet exciton-accepting organic molecules have emerged as promising materials for converting incoherent long-wavelength light into the visible range. However, these materials to date have made exclusive use of nanocrystals containing toxic elements, precluding their use in biological or environmentally sensitive applications. Here, we address this challenge by chemically functionalizing non-toxic silicon nanocrystals with triplet-accepting anthracene ligands. Photoexciting these structures drives spin-triplet exciton transfer from silicon to anthracene through a single 15 ns Dexter energy transfer step with a nearly 50% yield. When paired with 9,10-diphenylanthracene emitters, these particles readily upconvert 488-640 nm photons to 425 nm violet light with efficiencies as high as 7 ± 0.9% and can be readily incorporated into aqueous micelles for biological use. Our demonstration of spin-triplet exciton transfer from silicon to molecular triplet acceptors can critically enable new technologies for solar energy conversion, quantum information and near-infrared driven photocatalysis.

Hybrid materials comprised of inorganic quantum dots functionalized with small-molecule organic chromophores have emerged as promising materials for reshaping light's energy content. Quantum dots in these structures can serve as light harvesting antennas that absorb photons and pass their energy to molecules bound to their surface in the form of spin-triplet excitons. Energy passed in this manner can fuel upconversion schemes that use triplet fusion to convert infrared light into visible emission. Likewise, triplet excitons passed in the opposite direction, from molecules to quantum dots, can enable solar cells that use singlet fission to circumvent the Shockley-Queisser limit. Silicon QDs represent a key target for these hybrid materials due to silicon's biocompatibility and preeminence within the solar energy market. However, while triplet transfer from silicon QDs to molecules has been observed, no reports to date have shown evidence of energy moving in the reverse direction. Here, we address this gap by creating silicon QDs functionalized with perylene chromophores that exhibit bidirectional triplet exciton transfer. Using transient absorption, we find triplet transfer from silicon to perylene takes place over 4.2 μs while energy transfer in the reverse direction occurs two orders of magnitude faster, on a 22 ns timescale. To demonstrate this system's utility, we use it to create a photon upconversion system that generates blue emission at 475 nm using photons with wavelengths as long as 730 nm. Our work shows formation of covalent linkages between silicon and organic molecules can provide sufficient electronic coupling to allow efficient bidirectional triplet exchange, enabling new technologies for photon conversion.