Abstract
Accurately extrapolating a moving object’s trajectory when it becomes occluded is useful in everyday situations such as crossing a busy street or passing another car. Interestingly, recent research has shown that people tend to underestimate a moving object’s speed behind an occluder. Here, we aimed to determine whether this occlusion bias depended on the type of action: discrete vs. continuous. We presented a bar that moved across the screen with constant velocity and went behind an occluder for the second half of its movement. Participants estimated the moment that the bar reached the goal position by pressing a button or reaching and touching the goal position to stop the moving bar. The original occlusion bias was shown using a button press task. We reasoned that reach might reduce the bias based on prior findings that time perception improves with concurrent continuous movement. In line with the previous occlusion bias findings, we observed that participants were more likely to stop the bar after it passed the goal position. However, contrary to our expectations, the occlusion bias was mostly similar across button press and reach. Next, we examined whether the occlusion bias was present at the perceptual level of analysis. Participants judged whether a tone was presented before or after the bar reached the goal position. A perceptual occlusion bias was present but less pronounced than action (~80ms for perception vs. ~130ms for action). Overall, the bias was roughly constant across various motion durations and directions and grew over trials, replicating the previous findings. These results may point to a limitation where the visual system “blinks” when a moving object goes behind an occluder, creating a lag in motion estimation for perception and action.