Drosophila learn to prefer immobile spherical objects through repeated physical interaction

Animals interact with unfamiliar objects to learn about their properties and guide future behavior, but the underlying neurobiological mechanism is not well understood. Here, we developed a behavioral paradigm in which freely walking Drosophila melanogaster are repeatedly guided to spherical objects using a visual cue. Flies exhibited diverse and structured object interaction motifs, including "ball pulling" and "ball walking," that evolved over time. Notably, flies developed a strong preference for immobile over mobile spherical objects, despite their near-identical appearance, suggesting that they learn about the object's stability through physical interaction. This preference was impaired by silencing specific hΔ neurons in the fan-shaped body, previously implicated in spatial navigation but not known to contribute to "object interactions." Our results show that hΔ neurons also modulate object interaction motifs and the fidelity of following visual guidance cues, pointing to a role in balancing goal-directed and exploratory behaviors. These findings establish Drosophila as a model for investigating how internal representations and multimodal feedback contribute to adaptive object interaction. VIDEO ABSTRACT.