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. Methods The data from two experimental tasks was collected using a robotic arm manipulandum (KINARM). Each ‘.mat’ file contains one participant’s data for an entire experimental session. Experiment 1: participants performed a temporal bisection task while being allowed to freely move the robotic arm throughout the planar workspace. Each of these trials began with the manipulandum locked in a central location, then a warmup phase signaled that the hold was released and they were free to move. Then, they were presented with a 440 Hz tone that ranged from 1000-4000 ms, and at the end of the tone, judged whether it was ‘short’ or ‘long’ compared to all the tones heard so far. They moved the cursor to one of two equidistance target locations (counterbalanced target assignment) on the screen to signal their choice. Additionally, the movement environment randomly varied on each trial such that a viscosity of 0, 12, 24, or 36 Nm/s was applied. Experiment 2: a separate set of participants timed the same range of intervals with the same viscosity values, but instead completed a temporal reproduction experiment. For the encoding phase, the robotic arm was locked in one of 16 start locations on the screen (randomized on each trial). They began moving upon receiving a visual cue, and in this experiment, tone presentation began when movement was detected. Trials were discarded and repeated if movement stopped during tone presentation. As soon as the tone was finished, the manipulandum was moved to a central location, and participants reproduced the duration by holding and releasing a button attached to the manipulandum. This dataset includes trial data for all participants. Each ‘mat’ file contains two main cells: ‘info’ and ‘dat’. The ‘dat’ contains structure arrays with information for all trials performed, and the info folder holds much of the same data, but nested as variables→trials instead of trials→variables. Please see ReadMe files for more detailed information.