Slowing the body slows down time (perception)

Interval timing is a fundamental component of action, and is interestingly susceptible to motor-related temporal distortions. Several experiments have shown that temporal expansion and compression can occur in systematic ways with modifications of movement direction, speed, and length. These studies have largely shown that movement biases temporal estimates, but have primarily considered self-modulated movement only. However, real-world encounters often include situations in which movement is restricted or perturbed by environmental factors. Thus, in the following experiments, we introduced viscous movement environments to externally modulate movement speed and length, and investigated the resulting effects on temporal perception. We hypothesized that the decrease in movement length would bias estimates to be shorter as well. Participants timed auditory intervals while moving a robotic arm manipulandum that randomly applied four levels of viscosity. This added restriction successfully shortened the length of movement possible within a given time interval, and yielded compression effects both in temporal bisection and reproduction tasks. Using a drift-diffusion model and a Bayesian observer model, we confirmed that these biasing effects arose from perceptual mechanisms, instead of biases in decision making. These findings suggest that environmental perturbations are an important factor in movement-related temporal distortions, and more broadly, enhance the current understanding of the interactions of motor activity and cognitive processes.