QUESTION: Please explain this apparently common phenomenon: You are trying to remember the name of someone you knew a long time ago. Despite earnest and repeated attempts to recall the name, it eludes you. When you are no longer trying to think of it, the name suddenly pops into your brain.
– Andrea Harter, Carlsbad
ANSWER: The very mechanisms that help us concentrate can cause thoughts to shy away from us like skittish horses, only to return when we have stopped pursuing them.
To make knowledge more accessible, our brains suppress conceptual distractions through a process known as retrieval-induced forgetting. Researchers have most commonly studied this active process of forgetting using word retrieval tests.
For instance, people learn lists of category-exemplar pairs (fruits-apple, fruits-plum) from several categories (fruits, sports, cars). They then practice retrieving some of the exemplars, when cued with the category and the first two letters of the exemplar. Later, they are given the categories and asked to recall all the studied exemplars.
As expected, retrieval practice improves recall of the reviewed material. Surprisingly, recall of the unpracticed material is worse than it is with no retrieval practice at all. In other words, recall of one memory suppresses related memories.
Brain imaging has shown that retrieval-induced forgetting is adaptive because it reduces demands on the cognitive control mechanisms needed for recalling one of the competing memories.
Unfortunately, it also trips us up when we are searching for that less used memory. It has even been shown to be responsible for what can easily seem like pretentious lapses of native-language words in novices after immersion in a foreign language.
Retrieval-induced forgetting shuts off when we are no longer actively trying to recall a memory. The thread of a related memory can then lead us to the forgotten memory. Memories are more like spider webs than file folders, because different aspects of a memory (such as someone's name, image, an event involving the individual) are stored in different parts of the brain.
Mood affects forgetting and recall. Studies have shown that positive moods enhance retrieval-induced forgetting, and negative moods inhibit it. Positive moods should also facilitate later recall because positive moods encourage global processing of information and the forging of connections between related ideas, whereas negative moods encourage item-specific processing.
A particularly intriguing insight into recall comes from people with synesthesia – a mixing of the senses. When they have a word on the tip of the tongue, synesthetes who experience tastes elicited by words can taste the upcoming word before they can retrieve and say it.