If University of Maryland professor Michael Dougherty parks in a different spot than usual, he has to memorize where it is or he won't be able to find his car.
"I form an explicit intention to remember where I parked, encoding a contradiction to my normal behavior," says Mr. Dougherty, associate professor of psychology and director of the college's Memory and Decision Processes Laboratory. He holds a doctorate in psychology.
Mr. Dougherty uses mnemonic devices to help him remember his parking spot.
Mnemonic devices — such as thinking of a visual image; developing an acronym, rhyme or sentence; or repeating the information — are the best way to improve the ability to remember new information, according to metro-area psychologists.
Information enters, or is encoded, into the brain through the senses, then is stored temporarily in short-term or working memory, says John Philbeck, associate professor of psychology at George Washington University.
"At that stage, the information either can be forgotten, or you can keep it in working memory by repeating it, or it gets transferred into longer memory storage," says Mr. Philbeck, who also holds a doctorate in psychology.
A part of the brain called the hippocampus is crucial for transferring memory from working memory, where information can be recalled for several seconds without rehearsal, to long-term memory, which can store large quantities of information for long periods of time, Mr. Philbeck says.
"The hippocampus works as a memory indexer and is vital in the construction and reconstruction of memory," says Gary Null, lecturer, educator and author of more than 70 books, including "Mind Power, Rejuvenate Your Brain and Memory Naturally," published in 2005. He holds a doctorate in human nutrition and public health science and lives in Manhattan.
The brain's frontal lobes are important in memory construction; the temporal lobes form and retrieve memories; and the occipital lobes link images from the eyes to images stored in memory, Mr. Null says in his book.
"All we know is which parts of the brain have certain functions, but how that happens, we can only guess," Mr. Null says.
Memory is classified as short-term memory and long-term memory.
Short-term memory can store up to seven items, plus or minus two, such as seven consonants or seven words, says Michael Gardner, professor and associate chairman of the department of educational psychology at the University of Utah in Salt Lake City. He is a member of the American Psychological Association and holds a doctorate in cognitive psychology.
"The more you rehearse something, the more probable it transfers to long-term memory," Mr. Gardner says.
Long-term memory is broken into several types of memory, including declarative or explicit, procedural or implicit, semantic, and episodic.
Declarative memory involves knowledge of facts, and procedural memory involves knowledge of how to do something or a skill, Mr. Gardner says. Semantic memory is knowledge of concepts and their relationships with each other, along with the way the world works, he says. Episodic memory is memory of personally experienced events, he says.
For example, what Mr. Gardner ate for breakfast is an episodic memory, while the concept of dinner is a semantic memory, he says.
The number of memories stored over a lifetime is small in comparison to the number that are formed, says James Olds, director of the Krasnow Institute for Advanced Study, the center for the study of neuroscience at George Mason University. He is a Shelley Krasnow university professor of neuroscience and holds a doctorate in neuroscience.
"We think connections between individual nerve cells are strengthened in each unique way for each memory," Mr. Olds says. "All 100 billion nerve cells in the brain are separate, but they can communicate with each other. With more memories, the strength of the connection goes up."
Each nerve cell can participate in hundreds of different memories, and each memory requires the participation of thousands of nerve cells, Mr. Olds says.
"When you have a memory, you're sensing different things about your environment," he says. "Those sensations need to be encoded by nerve cells."
The strength of the connections can increase or decrease, in which case, the memory may be forgotten, Mr. Olds says.
"Our memories are so fallible and get erased so quickly, we build stories around the memories we have," he says. "For any particular period of our lives, we can remember generalities."
The durability of a memory has to do with how many associations are stored with the memory, Mr. Philbeck says.
"It's thought that when we're exposed to information, that generates a pattern among neurons in the memory centers of the brain," he says. "The more times that pattern tends to get re-created, it gets reinforced."
Mnemonic devices are a way to create more associations through the use of cues to remember new information, Mr. Philbeck says.
The devices help organize the information, such as by chunking, which is arranging a list of items into smaller categories, or tying the information to something already known, says Elizabeth Phelps, professor of psychology and neuroscience at New York University in New York City. She reviews grants for the National Institute of Mental Health in Bethesda and holds a doctorate in psychology.
"Anybody can do this. Of course, it takes effort and desire to learn how to use memory tricks," Ms. Phelps says.
"Memory is not meant to be perfect," she says. "Memory is fallible. Forgetting is a natural part of remembering."