Rapid adaptation to acceleration during interceptive hand movements

Real-world objects in our environment rarely move at a constant speed but usually accelerate or decelerate. Yet, human perception is highly insensitive to visual acceleration. When manually intercepting moving objects, humans commonly ignore acceleration, resulting in systematic interception errors (Kreyenmeier et al., 2022, eNeuro). Here we ask whether humans’ ability to manually intercept accelerating targets improves during repeated exposure to the same rate of acceleration. In a track-intercept task, observers (n=9) tracked the ramp of a small target either moving at constant speed (0 deg/s/s), accelerating (+8 deg/s/s), or decelerating (-8 deg/s/s). After 800 ms, the target disappeared behind an occluder and observers had to rapidly point at the target at the predicted time of reappearance from behind the occluder (time-to-contact; TTC). Observers performed blocks of twelve trials during which they were exposed to the same rate of acceleration. During the first eight trials, the occluder had a fixed width (reference), in the remaining four trials, the occluder was either narrower or wider than the reference (test). In the first trial of each block, observers systematically intercepted too late for accelerating targets and too early for decelerating targets, indicating that they did not take acceleration into account. Within the first four reference trials, they adjusted the timing of their hand movement to match veridical target TTC. In test trials, observers only partially accounted for acceleration and showed similar biases as in early reference trials. Our results show that humans can rapidly adjust the timing of their hand movement to intercept accelerating targets. However, their ability to transfer this adjustment to new TTC conditions is limited. These findings provide further evidence for the inability to decode accelerating motion and to accurately interact with accelerating objects.