Read more: “Instant Expert: Memory“
Unlike a DVD or computer hard drive, our brains do not faithfully replay our previous experiences as they happened. Certain pieces of information and events stick in the mind but others disappear or become distorted, and sometimes we even seem to remember things that never happened. Over the past few decades, researchers have built a good understanding of the factors that influence the contents of our memories.
Encoding and processing
Several important factors influence how well we remember, starting with the way we process information at the time of encoding. In the 1970s, and at the University of Toronto, Canada, described different levels of processing, from the “superficial”, dealing only with the physical properties of what is to be remembered, through to “deeper” processes that explore the semantics of the material. Suppose you were asked to study a list of words, for instance. If you were asked to provide a definition of each word as you study it, you would be much more likely to remember the list than if you were asked to count the number of vowels in each word. This not only shows that “deep” processing aids memory, but is a good illustration of the fact that we are active, rather than passive, agents in the remembering process.
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Context can also exert important effects on memory. For example, in some famous studies, divers were asked to remember information when they were either on the shore or beneath the water’s surface. They were then asked to recall the information at a later time – again, either on land or underwater. Their recall turned out to be substantially better when the learning and test sessions occurred in a similar environment; they remembered information learned under the sea more clearly if they were tested underwater than if they were tested on the beach, and vice versa.
Your physiological or psychological state can have a similar effect. This is potentially significant for students studying for exams. If you revise while you are calm, but then feel nervous or excited in the actual examination, you might not recall information so well compared with someone whose mood is more even across study and test. Equally, you may be more likely to remember a night’s escapades when you are next drunk than when you are sober.
Flashbulbs and reminiscence
Certain events seem to stay with us as particularly vivid memories for years afterwards. This is especially true if the events are unusual, arousing or associated with strong emotions.
The assassination of John F. Kennedy in 1963, the death of Princess Diana in 1997, and the events of 9/11, for instance, are all very memorable for people who were alive when they occurred. Memory for such events appears to be very resistant to forgetting – many people are able to remember where they were and who they were with when they heard the news, even decades later. This is what has been termed flashbulb memory.
Another common phenomenon, known as the reminiscence bump, refers to the wealth of memories that we form and store between adolescence and early adulthood. When we are older, we are more likely to remember events from this period than any other stage of life, before or after. It could be that the reminiscence bump is due to the particular emotional significance of events that occur during that period, such as meeting one’s partner, getting married or becoming a parent, and events that are life-defining in other ways, such as starting work, graduating from university or backpacking around the world.
Flashbulb memories and the reminiscence bump are the subject of much debate. For instance, some have questioned whether the rich details that we seem to recall in a flashbulb memory may in fact have merely been inferred from our general knowledge of the event – we may recall details of the fatal car accident in which Princess Diana died due to the fact that it has been replayed in the media many times since 1997.
Imagined memories
It is very easy to lead someone’s memory astray. For example, if I witness a traffic accident and I am later asked whether the car stopped before or after the tree, I am much more likely to “insert” a tree into my memory of the scene, even if there was no tree present. This occurrence reflects the fact that when we retrieve a memory, we also re-encode it, and during that process it is possible to implant errors.
at the University of California, Irvine, and colleagues have shown that this “misinformation effect” could have huge implications for the court room, with experiments repeatedly demonstrating that eyewitness testimonies can be distorted by misleading questioning. Fortunately, their findings also suggest ways for police, lawyers and judges to frame the questions that they ask in a way that makes reliable answers more likely.
Related to the misinformation effect are “recovered” and false memories. A team led by at Washington University in St Louis, Missouri, has built an extensive body of research showing that false memories can be formed relatively easily. People can be encouraged to “remember” an item that is linked in its meaning to a series of previously presented items but which itself was not presented. Suggestions and misleading information can create “memories” of personal events that the individual strongly believes to have happened in their past but which never took place. In one famous experiment, Loftus persuaded subjects that they had seen Bugs Bunny at Disneyland, despite the fact that he’s a Warner Bros character. Such findings may represent a serious concern for legal cases in which adults undergoing therapy believe that they have recovered memories of abuse in childhood.
“Memories of events like the assassination of John F. Kennedy are very resistant to forgetting”
