From the flow of liquids to the flow of time: Granularity of spontaneous liquid flow predictions in visual perception impacts experienced time

The flow of time ordinarily guides intuitive physics: in a visual scene, we spontaneously predict what will happen next, and can reason about what might have happened. Does intuitive physics in return impact how we experience time? Experienced duration of time is malleable and this plasticity has been suggested to reflect the intensity of cognitive processing, with more processing corresponding to subjective durations lasting longer than actual durations. Here, we suggest that spontaneous intuitive physical predictions during visual perception adaptively engender representations of various granularities, and such representational granularity impacts the experienced duration of time. A coarse-grained representation might suffice to predict whether a liquid will flow toward right or left, while a finer-grained simulation may be necessary to work out details of its trajectory. We predict subjective time will slow down in the latter case. Observers watched animations with differently-oriented “planks”, through which liquids would flow. To manipulate the granularity of simulations, we placed a row of vertical pegs at the bottom faced either Upwards (to encourage finer-grained processing — since the liquid could fall into only some of the narrow openings), or Downwards (to encourage coarse-grained processing — since it doesn’t matter here where the liquid would fall). Without an overt intuitive physics task (i.e., no mention of prediction), observers simply reproduced the duration of animations by holding a key down. Across experiments, observers experienced animations with Upwards pegs as lasting longer than those with Downwards pegs. Critically, granularity independently modulated subjective time above and beyond mere predictability since these results held across animations that were highly predictable (when the liquid’s viscosity made it more trackable) and ones that were more unpredictable (when using sparser Atari-like pixelated displays). Thus the granularity of our mental simulations may influence our experience of the flow of time itself.