A quintessential feature of human intelligence is the ability to create ad hoc conventions over time to achieve shared goals efficiently. We investigate how communication strategies evolve through repeated collaboration as people coordinate on shared procedural abstractions. To this end, we conducted an online unimodal study (n = 98) using natural language to probe abstraction hierarchies. In a follow-up lab study (n = 40), we examined how multimodal communication (speech and gestures) changed during physical collaboration. Pairs used augmented reality to isolate their partner’s hand and voice; one participant viewed a 3D virtual tower and sent instructions to the other, who built the physical tower. Participants became faster and more accurate by establishing linguistic and gestural abstractions and using cross-modal redundancy to emphasize key changes from previous interactions. Based on these findings, we extend probabilistic models of convention formation to multimodal settings, capturing shifts in modality preferences. Our findings and model provide building blocks for designing convention-aware intelligent agents situated in the physical world.

Realizing a designer’s intent in software currently requires tedious manipulation of geometric primitives, such as points and curves. By contrast, designers routinely communicate more abstract design goals to one another using an efficient combination of natural language and drawings. What would it take to develop artificial systems that understand how humans naturally convey design intent, and thereby enable more seamless interactions between humans and machines throughout the design process? First, it is vital to establish benchmarks that showcase the full range of strategies that humans use to successfully communicate about design intent. Here we take initial steps towards that goal by conducting an online study in which pairs of human participants – a “Designer” and “Maker” – collaborated over multiple turns to recreate target designs. In each turn, Designers sent messages containing language, drawings, or both to the Maker, describing how to modify an existing design toward the target. We found a preference for communicating using drawings in early turns and observed several multimodal strategies for conveying design intent. By comparing how human Makers and GPT-4V carried out instructions, we identify a gap in human and machine understanding of multimodal instructions and suggest a path for bridging this gap.