When you watch an athlete or dancer perform, does it ever feel like time is slowing down? That’s not just in your head! This phenomenon is known as time dilation, and it makes you feel like time is moving more slowly. This occurs when we observe complex biological motion, such as dancing or walking. For example, Sabrina Carpenter recently went viral for her live performances of the song Juno, where she struck unique poses at each concert venue. Moments like this feel like they last forever, making it easier to understand what’s going on and remember details. But why does this happen?

Some scientists say that when we watch people moving, our brains engage in a process called mental simulation, where we imagine we are performing the same movement. Surprisingly, our posture can affect how well this works. Mental simulation might engage our muscles, so our body posture can sometimes make it easier or harder to do simulations. For example, compared to sitting, standing engages more muscles and reduces the connection between your brain and the rest of your body, making mental simulation more difficult.

Both mental simulation and time dilation seem important to understanding biological motion, so in their latest research published in Psychonomic Bulletin & Review, Li Shen, Xiaorong Cheng, Zhangjing Ma, Hexing Zhong, Xiaofei Jiao, Ying Wang, Yi Jiang, Zhao Fan*, and Xianfeng Ding (*pictured below) explored how they relate to each other. Their study looked at people in three different postures: sitting, standing, and paraplegic spinal cord injury (PSCI). Relative to sitting, people who are standing or have permanent spinal cord injuries have a harder time accessing their muscles, which should make mental simulation more difficult. In turn, they expected that these postures would reduce time dilation.

In their study, participants were shown two back-to-back videos: one of a person walking (displayed as moving dots, as shown in the image below) and an upside-down version of the same video. The videos played for different lengths of time, and viewers had to say which one felt longer. They did this for the videos of people walking, as well as mixed-up versions of the same videos. Showing participants these natural and mixed-up videos allowed the researchers to see how time dilation differs between biological motion, which looks like someone walking, and other kinds of motion.

For both kinds of videos, as shown in the figure below, the researchers found more time dilation for sitting compared to standing, supporting their initial predictions. They also found that, compared to standing, people with PSCIs showed normal time dilation for regular biological motion, but reduced time dilation for the mixed-up videos. This suggests that these individuals are able to compensate for their inability to simulate motor activity when viewing biological motion, but this compensation doesn’t seem to apply to other kinds of motion.

This finding tells us something very interesting: People with permanent spinal cord injuries seem to slow down time to process biological motion, even though they can’t simulate it the same way as others. After injuries like this, the brain quickly reorganizes itself to process real human movement even without physical simulation. This reorganization might explain how they still experience time dilation for real movement.

To sum it up, the researchers say:

“The study reveals that sensorimotor simulation is critical for processing local biological motion cues, while permanent sensorimotor loss triggers selective compensation via global configuration cues, underscoring the distributed, embodied nature of biological motion perception.”

It seems that when we simulate motion, we gain a better understanding of the world around us. The findings also imply that our understanding of movement is tied to our bodies. Even when parts of the body can no longer move, the brain finds new ways to make sense of movement. This type of research can help improve areas such as physical therapy and virtual reality training. It shows us that good body posture can help us understand movement better!

According to this study, when you see someone move, your brain doesn’t just sit back and watch. Instead, it wants to join in and pretend to be a part of the action. So, when you’re watching a sports game or a concert performance, and it feels like time slows down, your brain might be asking Have you ever tried this one?

Featured Psychonomic Society article

Shen, L., Cheng, X., Ma, Z., Zhong, H., Jiao, X., Wang, Y., Jiang, Y., Fan, Z., & Ding, X. (2025). Sensorimotor simulation and distributed processing of biological motion: Insights from healthy and paraplegic adults. Psychonomic Bulletin & Review, 1–11. https://doi.org/10.3758/s13423-025-02689-3