The information variables for controlling manual transfer of liquid-filled containers.

It is a familiar but challenging task to manually transfer a liquid-filled container without spilling. The action requires stringent control because the dynamics of interacting with the non-rigid aqueous content is complex. In this work, we sought to discover what properties of a liquid-filled container were predictive of transfer without spilling performance. Two candidate variables were tested (Experiment 1): The distance between liquid surface and the container's rim (h) and the container's diameter (d). Participants attempted to transfer 15 containers (3 ds and 5 hs), one at a time and as fast as possible, without spilling. Kinematic analyses showed that the movement's peak velocity and the first peak acceleration were affected by h; the movement time and the frequency of acceleration change were affected by h and d in a hierarchical manner, where transfer without spilling was first affected by h and for full containers, the thick ones were moved more slowly and went through more acceleration change; for not so full containers, the container's diameter did not have any effect. Next, each of the 15 containers was compared with the other 14, and participants judged from a pair of displayed containers which one was more likely to be moved fast without spilling (Experiment 2). Perceived affordance was affected by h and d but not by whether containers were placed upright or tilted. In general, thinner and less full containers were judged as easier to be moved fast without spilling.