Our experience of time feels like a continuous stream, but our brain doesn’t store this information as one long recording. It actively breaks down the flow of life into distinct events, creating mental “chapters” from the narrative of our existence. This process, known as creating temporal transitions, allows us to organize our complex world. It transforms sensory input into a structured story, making our experiences manageable and meaningful.
The Brain as a Story Editor
Your brain functions much like a film editor, constantly making cuts to segment the flow of information into coherent scenes. This active process is called event segmentation. The brain searches for specific cues that signal a change in context, which then serves as a boundary marker to close one “event file” and open a new one.
Event Segmentation Theory (EST) proposes this process relies on creating “event models,” which are working representations of what is happening at any given moment. These models help us predict what will happen next. When a prediction fails—for instance, when we move to a new location or start a new task—the brain registers a “prediction error.” This error signals that the current event model is no longer accurate.
This updating process is what creates the event boundary. By chunking our experiences this way, the brain makes them easier to process and remember. This organizational system is fundamental to how we comprehend and recall the events of our lives, allowing us to navigate our world with a structured understanding.
This segmentation is not a random process and has a direct impact on memory. Individuals who create more event boundaries, or whose boundaries align more closely with normative patterns, often show better recall for the details of those events. This suggests that segmenting experience is an adaptive cognitive tool that helps to efficiently encode information.
Neural Signatures of Time’s Chapters
The process of event segmentation has biological roots within the brain’s circuitry. When one event has ended and another has begun, there is a corresponding shift in neural activity. This change serves as a biological marker for the temporal boundaries we perceive. fMRI studies have shown these moments are associated with increased activity in a network of brain regions, particularly the posterior and frontal cortex.
At the heart of this network are the hippocampus and the medial prefrontal cortex (mPFC). The hippocampus is involved in forming detailed, context-rich memories, while the mPFC helps organize these memories by integrating new information. When an event boundary is detected, communication between the hippocampus and mPFC increases, facilitating the “closing” of the previous memory file and opening a new one.
These neural shifts are not just a reaction to a boundary but are part of the mechanism that creates it. Relatively stable patterns of brain activity, called neural states, correspond to the duration of an event. When the context changes, this pattern is disrupted, and a new stable pattern begins to form, reflecting the new event.
This neural organization follows a hierarchy. Lower-level sensory areas segment information on very short timescales, reacting to immediate physical changes. In contrast, higher-order regions like the prefrontal cortex create boundaries based on more abstract changes, such as a shift in goals, resulting in longer event chapters.
The Doorway Effect and Memory Gaps
A common consequence of event segmentation is the “doorway effect.” This is the familiar experience of walking into a room and immediately forgetting your purpose for being there. This lapse in memory is a direct result of crossing a physical threshold, which acts as a powerful event boundary for the brain.
When you walk through a doorway, your brain perceives a significant change in context. This shift triggers the location-updating effect, where the brain decides information from the previous room may no longer be relevant. In response, it archives the previous event model to free up cognitive resources for the new environment. The intention you formed in the other room gets bundled away with that archived memory file.
This phenomenon highlights how our memory is organized episodically, with each episode tied to a specific context. Information within the current event is more readily accessible than information from a previous one. The doorway serves as a mental dividing line, making it harder to retrieve thoughts from the “chapter” that just concluded. Studies using virtual reality have demonstrated this effect.
The strength of the doorway effect can be influenced by cognitive load. If you are multitasking or distracted, your working memory is already strained and more susceptible to the interference caused by an event boundary. This experience demonstrates how the brain’s automatic filing system can sometimes be too efficient, tucking away information we still need.
Why Time Seems to Speed Up or Slow Down
Our subjective feeling of time’s passage is a different, though related, phenomenon from the segmentation of events. While event boundaries break our experience into chapters, our perception of the length of those chapters can stretch and shrink. This is not about how memories are organized, but about how we experience duration in the moment and in retrospect.
Emotion is a modulator of time perception. Intense feelings, particularly fear or awe, can make time seem to slow down. This is because the brain dedicates more resources to processing information during highly emotional states. This leads to a richer, denser memory of the event that feels longer when we look back on it.
Attention also plays a role. When you are deeply engaged in a task, a state called “flow,” time can appear to fly by because your attentional resources are focused on the activity, not on time’s passage. Conversely, when you are bored or waiting, your attention is directed toward time, making each second feel prolonged.
Finally, novelty influences how we remember the duration of past events. As we age, life often becomes more routine, and we encounter fewer new experiences. Because the brain processes familiar information more efficiently, these periods create fewer detailed memories. A month filled with novel experiences will seem much longer than a month of repetitive activities, explaining why time often feels like it accelerates as we get older.