You enter your living room, then pause. You feel your mission’s momentum— but its aim is suddenly lost. So, what just happened? And why does it keep happening? Well, you’re not alone; this is actually a common phenomenon scientists have termed the doorway effect. According to psychological models, our brains parse life’s continuous flow of time and activity into distinct events. As a situation unfolds, the brain develops a working model of the event. It likely does this by employing its default mode network, the brain regions that work together to accomplish many resting thought processes. Then, when there's a big enough change, the brain is thought to identify an event boundary, at which point it stores the prior event model, and begins developing a new working model. During this switch, called an event update, parts of the default mode network seem to interact with the memory-storing hippocampus, perhaps transporting the experience into longer-term memory. In the process, the brain clears its short-term memory, making room for the new information that’s already pouring in. But sometimes that can be stuff you weren't quite done with. It’s still not fully clear if the doorway effect, also called the location updating effect, befalls some people more than others. But one study found that age had very little bearing. Scientists are working to better understand the phenomenon by pinpointing the conditions that trigger it, which, yes, includes doorways, both physical and virtual. In one study, college students in real and virtual spaces were asked to pick up objects, walk set distances carrying them out of view, then try to recall what they were holding. Time and distance remained constant, but some traveled through a doorway. Those who did tended to respond slower and be more likely to forget. And passing through multiple doorways seems to worsen the memory-thwarting effect. It's also not helped by multitasking. In another VR experiment, participants were first asked to memorize the colors and shapes of different objects. Then, some moved across the same room while others entered another. When they were asked to also complete a counting task, those who traveled through the doorway had a harder time recalling the original objects. Moving through the doorway distracted seemed to somehow overload their memory. But the effect plagues people beyond literal doorways. Looking through clear walls into adjacent rooms also appears to do the trick. And really, whatever triggers an event update is thought to do the same: an alarm ringing; a friend changing the subject; or a shift in location, time, motivation, or computer tab. Likewise, when people come upon an event boundary while reading stories, like a sentence describing a considerable time jump, researchers have observed that their reading speed may slow, their neural activity increases, and they have more difficulty answering questions about what a character was just doing. But this isn't always the case with event updating. In certain circumstances, doorways actually seem to aid memory. In one study, participants were given lists of words, and in between them, they either moved spots within one room or walked into another. Those who switched rooms wound up recalling the words more faithfully. The key difference in a doorway’s ability to strengthen versus muddle memory might be the act of separating information into discrete events versus sharing it among multiple. This may result in clearer compartmentalization that helps reduce competition and interference when trying to recall the information. Generally, event updating is the brain attempting to adapt to new situations. But the doorway side effect can be disorienting. So, how can we best pick our train of thought back up? Thankfully, the confusion tends to resolve on its own. But retracing your steps may help jog your memory. And people have also suggested that attempts at deliberately preventing the doorway effect can help, consciously keeping their goal in mind— perhaps repeating it verbally. Really, whatever helps you stay caught up so your head doesn’t get ahead of you.