Do you remember what you had for dinner last night? What about dinner last week? How about the name of your second-grade teacher?
Your memory is built in three basic steps. Before you can remember something, you have to learn it. This is called "acquisition"—you acquire the information, and your brain places it in short-term memory. This is where the information about last night's dinner ends up.
If you want to remember something for a longer period—your address, for instance, or the Gettysburg Address—you need to place the information in long-term memory. To do this, your brain strengthens and reinforces the nerve pathways where that memory resides. This process, called "consolidation," can take weeks or months of repeating and reviewing the information, according to Harvard Medical School.
The third step in memory is getting at the information you have stored away. This is called "retrieval." You retrieve the information from the nerve pathways where it was stored. The retrieval process can be quick or slow. It depends on how well you learned the information.
Memory has other aspects beyond these three areas. When you try to remember a name of a person or place, you may feel frustrated that you can't quite get it. That's the "tip-of-the-tongue" phenomenon, says Alan Searleman, Ph.D., a psychology professor at St. Lawrence University. "You know you know it, but you just can't put your finger on it," he says. Your brain has the information, but you have no easy way to retrieve it. We can remember in degrees, which is why you may recall that an acquaintance's name starts with an "P" but be unable to recall anything more.
Another phenomenon is called déjà vu, which is French for "already seen." Some experts say that certain aspects of a place or event might trigger similar memories, causing the feeling of déjà vu. Another theory is that it's just a short circuit in the brain. "Nobody really knows for sure. That's why people attribute it to things like reincarnation," says Kenneth Higbee, Ph.D., a psychology professor at Brigham Young University.
The opposite phenomenon from déjà vu is called jamais vu, or French for "never seen." When this occurs, people or places that should be familiar are not, Dr. Higbee says. Let's say you run into a co-worker at the shopping mall. You may remember the face, but nothing else. "That's because the context in which you know her has changed," says Dr. Searleman.
It's easier to remember faces than names because remembering faces involves recognition, a much simpler process than recalling a name, says Dr. Searleman. "In recognition, the retrieval cues you stored in your brain as memories are staring you in the face; all you have to do is recognize them." But in recalling names, you may not have a retrieval cue. Once you get a cue, your memory will suddenly feel less sleepy.