Why is memory often unreliable?
The brain and body change so much over a lifetime, but like the hands of a clock, it can be difficult to perceive these changes. For example, red blood cells are completely replaced every four months. On a physical level, you are constantly renovating and becoming a new you.
Fortunately, there is one constant element that connects these different versions of you: memory. Memory becomes the thread that weaves your identity image, providing a continuous, unique sense of self.
However, there may be a problem here: Is continuity just an illusion? Imagine you walk into a park and meet versions of yourself in different ages. You sit together, share the same life story, and tease out your one and only thread of identity.
But can it really be done? You do share the same name and history, but you are really different people with different values and goals. The 15-year-old you you remember are not the same as when you were 15, and you have different recollections of the same events.
Here’s an example: You celebrate a friend’s birthday, and one year after the birthday party, two of your friends break up. Thinking back to that get-together, you may now mistakenly recall that the red flags were on the line. There seemed to be some awkward silence between the two that night? These details are hard to pin down, because the corresponding knowledge in your neural network changes the associated memory. Therefore, the perception of the same thing is likely to be very different at different stages of life.
Your memories of birthday parties have started to fade. Because the number of neurons is limited, and they all need to multitask. As these “birthday” neurons synergistically participate in other memory neural networks, the memory of your birthday party becomes blurred.
The enemy of memory is not time, but other memories. Our past is not a faithful record, but rather a reconstruction, almost a story at times. When we review our own life memories, we should realize that not all the details are accurate.
Why does time sometimes feel slower?
When I was eight years old, I fell off the roof and it seemed to take a long time to fall. When I learned physics, I calculated how long it took to fall, and it was only 0.8 seconds. Why does it feel like it’s taking so long?
In many life-threatening experiences, such as car accidents or robberies, or seeing a loved one in danger, such as a child falling into a lake, people report experiencing a subjective experience of time slowing down. The subjective feelings in all these reports have a common feature. The reporters all feel that the events are unfolding more slowly than normal, with a wealth of detail. What happened in my brain when I fell off the roof? Does time really slow down in dire situations?
The answer appears to lie in the way memories are stored. Under threat, a region of the brain called the amygdala kicks into high gear, mobilizing resources from the rest of the brain to deal with the situation at hand. When the amygdala is active, it retains memories in far greater detail than normal, activating a secondary memory system.
After all, that’s what memory is for: to keep track of important events so that if a similar situation comes up again, the brain has more information to use to survive. In other words, if something is life-threatening, it’s time to take good notes. An interesting side effect of this is that the brain is not used to that memory density, so when the event plays back in memory, the interpretation is that it must have lasted longer.
We don’t really experience the horrific accident in slow motion, it’s a trick when reading memories. When we ask what happened just now, the details of the memory tell us that we went into slow motion, when it didn’t. Time distortion is a phenomenon that occurs in retrospect, and it is the ghost of memory.
