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Did I lock my door? I don’t know. I don’t remember. I have a phenomenal number of memory failures like this. Did I respond to that email or merely think about responding? Have I told my class about this before? What was I supposed to get at the store today? I'll bet that you have these errors frequently, too. But the real question is, Should we worry about these small, consistent, everyday memory failures?
In order to know if these small memory errors are incipient signs of cognitive decline, we should consider the nature of these everyday failures. Many of these memory failures reflect reality monitoring problems. Reality monitoring is the task of knowing if you did some action or only thought about the action. Another version is knowing if you did something or dreamed about something. Generally, this isn’t so hard to track: The actions we perform leave behind memory records that are different from actions we think about. Memories of actions come with more complete recollections than memories of thought. Since you performed the action, you have information about what you thought, what things looked like, how the action felt, how things smelled, and what things sounded like. For real memories, you have a complete wealth of perceptual experience. Memories for what you only thought about doing have less complete recollections. When you think about such things, you generally have a less clear and complete sense of re-experiencing. Thus we aren’t constantly confused about what we’ve done and what we’ve only planned to do. The clarity and completeness of re-experiencing helps us perform accurate reality monitoring, allowing us to know what we’ve done and what we’ve only thought about doing.
But the reality monitoring system doesn’t work perfectly. The system fails because some of our thoughts and plans can be very detailed. This happens with actions that we’ve repeated many times. I’ve locked the door so many times that even simply thinking about it can be very detailed. This is also why dreams can feel so real. When you are in the midst of a dream it is very completely realized in terms of every perceptual detail you consider. Even more confusing is that you generally aren’t aware that you’re dreaming. When you are thinking about something, you generally know that you are only thinking and not actually doing something. The upshot is that some of our thoughts can be almost as real as our memories.
The system also fails because we often fail to focus on our actions. When I leave my office and pull my door closed, I am often already thinking about something else—typically, the class or meeting I am moving toward. Of course, this means I am not paying attention to closing my office door. So I can walk halfway down the hall and have no memory of whether or not I closed my door. And if you watch me walk away from my door, you will also frequently see me turn around to make sure that I closed it; I don’t know without double checking.
Reality monitoring predicts the situations in which we will most frequently fail to remember if we performed an action. It should happen for common activities so well known and so frequently completed that we can imagine them well, have difficulty keeping track of the myriad times we’ve performed them, and are so automatic that we perform them while thinking of something else. If you want to cut down on running back to check your door, repetitively clicking your car locking system as you walk away, and repeatedly telling people the same story, there is something that will help: Pay more attention to each action you perform.
Focus on each moment and spend less time thinking about the next thing you’ll be doing. This will help you develop more complete memories that will enable you to engage your reality monitoring system.
Are your memory failures indicative of a deeper cognitive problem? If most of your errors are forgetting if you’ve performed a very common action, probably not. If most of your errors occur because you tend to be thinking about other things while performing common actions, then definitely not. These are the situations that can lead to reality monitoring failures. And these everyday memory failures reflect normal cognitive functioning.
Personally, I’m rarely sure if I locked my door. But I am an absent-minded professor who frequently mind-wanders as I physically wander away from my office. So I turn around when I'm several feet away, to check one more time.
