Better performance when recalling speed from high-level compared to low-level motion

Our daily visual environment is abound with motion – people walk, snowflakes fall, and trains speed by. Accurately perceiving object speed is essential when avoiding collisions or intercepting moving objects. Accurately remembering object speed is equally essential, as moving objects may become temporarily occluded. Most studies of speed perception and memory use low-level motion stimuli (e.g., dot motion) which minimize spatial cues, but do not reflect the natural spatiotemporal dynamics of objects. In contrast, high-level motion stimuli contain rich spatial cues, better capturing real-world motion. Neural mechanisms underlying low- and high-level motion processing differ across the visual hierarchy. Might memory for speed also differ between low- and high-level motion? To answer this, we tested human participants on speed recall for both low- and high-level motion stimuli across different speeds (2–32 º/s) and delays (1, 4, or 8 s). Both types of stimuli moved along a circular trajectory (4–6 s) and were recalled via method-of-adjustment. Replicating previous work, we found a strong decrease in speed recall performance with increasing speed. Importantly, we also observed that recall performance was significantly worse for low- compared to high-level motion stimuli, implying an advantage for spatiotemporally bound objects. For high-level motion, longer stimulus and delay durations led to better and worse speed recall, respectively. Furthermore, there were direction congruency and hysteresis effects for both types of stimuli. Together, our results suggest that spatial cues facilitate speed estimation, and provide a solid psychophysical basis for understanding human short-term memory for speed.