Why does time fly when we’re having fun? Our sense of time may be the most basic foundation for all of our experience, but it’s an unsteady and subjective one, expanding and contracting, speeding up and slowing down. Emotions, music, everything in our surroundings, and shifts in our attention, all have the power to change how we perceive of time.
Last month in Nature Neuroscience, a trio of researchers at the Weizmann Institute of Science in Israel presented some important new insights into what impacts our experience of time. They found time perception is connected to two things: 1. The mechanism that helps us learn through rewards and punishments; and 2. Our expectations about what will happen next.
“Everyone knows the saying that ‘time flies when you’re having fun,’” said Sam Gershman, a cognitive neuroscientist at Harvard University who was not involved in the study. “But the full story might be more nuanced: Time flies when you’re having more fun than you expected.”
“Time” doesn’t mean just one thing to the brain. Different brain regions rely on varied neural mechanisms to track its passage, and the mechanisms that govern our experience seem to change from one situation to the next. But decades of research suggest that the neurotransmitter dopamine plays a critical role in how we perceive time. Dopamine’s association with time perception is intriguing, in part because the neurotransmitter is better known for its function in reward and reinforcement learning processes. When we receive an unexpected reward, we experience a rush of the chemical, which teaches us to continue pursuing that behavior in the future.
It’s likely more than a coincidence that dopamine is so fundamental to both time perception and learning processes. Learning itself is basically the association of a behavior with its outcome, and therefore requires the linking of one event with another in time.
When something unexpected but good happened — a “positive prediction error,” as researchers called it — the stimulus seemed to last longer. The unwelcome surprises of negative prediction errors made those experiences seem shorter. It basically tells us that our perception of time is going to be systematically biased by how surprised we are about outcomes.
The team showed that this pattern held quantitatively, with greater prediction errors correlating with greater distortions of perceived time. If humans stretch or contract their experience of time in response to signals, this might also alter their perceptions of how close or far apart certain actions and outcomes are — which could in turn influence how quickly those associations are learned.
There is still a lot to learn about the nature of how we experience time and the bidirectionality of learning, experience, and surprise.