Katakan Anda bertemu dengan orang baru. Let's say you meet someone new. The first time you see her, you take it all in: the length of her hair, the sound of her voice, that fresh shampoo scent that follows her around. As you're fumbling for an opening line, your hippocampus, a sea-horse-shaped area in your brain's temporal lobe, has already converted all these external stimuli into a memory. All potential memories must go through this mental gatekeeper before they take root in your mind. But the hippocampus is just a holding area, the first step in a complex process. After a memory has been forged, it's disassembled into its various sensory components, which are then distributed throughout the brain. Later, when you think of the person or happen to hear her name, see her face, or smell her hair, the components are drawn together again.
2. How alcohol affects your memory
Before it hits you over the head with a hangover, too much booze produces temporary amnesia by interfering with the ability of the hippocampus to create memories. (This is also known as a "blackout.") The memories that aren't lost can be especially tough to recall—unless you start drinking again and your brain taps into something called "state-dependent" memory. "When you encode memories while in a specific state, like being drunk, you're more likely to remember them when you're again in that state," says Jonathan Schooler, Ph.D., an assistant professor of psychology at the University of British Columbia. This may explain why Old School quotes start flying faster right around last call.
3. Why you can't remember being born
You might think something as traumatic as birth would leave its mark on your memory, but chances are you can only recall back to age 5. Why? One theory points to myelin, the protective nerve sheathing that helps with signal conduction; before age 5, a child's brain is low in myelin. "It may be important in long-term memory maintenance," says Schooler. Another possible explanation: As we learn to speak, we can no longer access memories created in our preverbal years. "With the onset of language, the way we think may change, making it impossible to get into the shoes of our older memories," Schooler says.
4. How memory stacks up to an iMac
It's a close race, but humans have the edge—for now. Our brains have about a thousand times the memory capacity of even the most sophisticated computer (though that could change by the year 2020). What's more, gray matter is a much more reliable storage device. Unlike computers, which store entire pieces of information in specific locations, the human brain spreads memories over many neurons. "This means that losing a single neuron doesn't have to affect memory performance," says David Leake, Ph.D., a professor of computer science at the University of Indiana.
5. How testosterone can help you remember
T may be essential for building memories as well as muscles. In a study at Oregon Health & Science University, men taking a drug designed to halt T production did significantly worse on verbal-memory tasks than men who weren't given the medication. "Animal studies have shown that if testosterone is taken away entirely, there's significant loss of the connections between neurons," says Jeri Janowsky, Ph.D., a professor of behavioral neuroscience and coauthor of the study.
Forget what you've seen on soap operas. "Retrograde amnesia, the total blackout of memory so beloved on television, is relatively rare," says Alan Baddeley, Ph.D., author of Your Memory: A User's Guide. When retrograde amnesia does occur, it's often due to severe psychological trauma rather than a nasty bonk on the head. A head injury would more likely cause anterograde amnesia, the condition featured in the movie Memento. "You can talk to someone with this condition and he'll be able to tell you his name, keep up with the conversation," says Michael Stadler, Ph.D., a professor of psychology at the University of Missouri. "But if you leave the room and come back 10 minutes later, he won't remember you."
7. Why you never forget how to ride a bike
When a child learns to ride a bicycle, he makes two sets of memories: One is explicit memory, which records things like the color of the bike and the elation of riding unassisted. Implicit memory, on the other hand, notes the body mechanics required to ride the bike, which is why it's sometimes called "muscle memory," says Janet Gibson, Ph.D., a professor of psychology at Grinnell College, in Iowa. Even when explicit memories fail, implicit ones remain.