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Memory researchers certainly haven’t forgotten Hermann Ebbinghaus, the first person to do scientific studies of forgetting, using himself as a subject. He spent a lot of time memorizing endless lists of nonsense syllables and then testing himself to see whether he remembered them. He found that he forgot most of what he learned during the first few hours after learning it.
Later researchers have found that forgetting doesn’t always occur that quickly. Meaningful information fades more slowly than nonsense syllables. The rate at which people forget or retain information also depends on what method is used to measure forgetting and retention. Retention is the proportion of learned information that is retained or remembered—the flip side of forgetting.
A forgetting curve is a graph that shows how quickly learned information is forgotten over time. Ebbinghaus made use of forgetting curves to chart his research on memory.
Measures of Forgetting and Retention
Researchers measure forgetting and retention in three different ways: recall, recognition, and relearning.
Recall is remembering without any external cues. For example, essay questions test recall of knowledge because nothing on a blank sheet of paper will jog the memory.
Recognition is identifying learned information using external cues. For example, true or false questions and multiple-choice questions test recognition because the previously learned information is there on the page, along with other options. In general, recognition is easier than recall.
When using the relearning method to measure retention, a researcher might ask a subject to memorize a long grocery list. The researcher might measure how long the subject has to practice before he remembers every item. Suppose it takes him 10 minutes. On another day, the researcher gives him the same list again and measures how much time he takes to relearn the list. Suppose he now learns it in five minutes. He has saved five minutes of learning time, or 50 percent of the original time it took him to learn it. His savings score of 50 percent indicates that he retained 50 percent of the information he learned the first time.
Causes of Forgetting
Everyone forgets things. There are six main reasons for forgetting: ineffective encoding, decay, interference, retrieval failure, motivated forgetting, and physical injury or trauma.
Encoding Failure: The way information is encoded affects the ability to remember it. Processing information at a deeper level makes it harder to forget. If a student thinks about the meaning of the concepts in her textbook rather than just reading them, she will remember them better when the final exam comes around. If the information is not encoded properly—such as if the student simply skims over the textbook while paying more attention to the TV—it is more likely to be forgotten. Encoding failure occurs when information is not properly processed or encoded into long-term memory. If the encoding process is incomplete or shallow (e.g., not paying full attention or using ineffective strategies), the information may never be stored in a way that allows for successful retrieval. This is why one may not recall the details of a conversation or where one’s keys were placed, because the facts were not deeply processed at the time.
Decay: According to decay theory, memory fades with time. Decay explains the loss of memories from sensory and short-term memory. However, loss of long-term memories does not seem to depend on how much time has gone by since the information was learned. People might easily remember their first day in junior high school but completely forget what they learned in class last Tuesday.
Interference: Interference theory has a better account of why people lose long-term memories. According to this theory, people forget information because of interference from other learned information. There are two types of interference: retroactive and proactive.
Retroactive interference happens when newly learned information makes people forget old information. For example, learning new material in a course might make it harder to recall information from previous class lectures. Proactive interference happens when old information makes people forget newly-learned information. For example, if you’ve memorized an old password, it might prevent you from easily remembering a new password.
Inadequate Retrieval: Forgetting may also result from failure to retrieve information in memory, such as if the wrong sort of retrieval cue is used.
Example: Dan may not be able to remember the name of his fifth-grade teacher. However, the teacher’s name might suddenly pop into Dan’s head if he visits his old grade school and sees his fifth-grade classroom. The classroom would then be acting as a context cue for retrieving the memory of his teacher’s name.
In cases wherein retrieval cues are insufficient or unavailable, it can lead to the tip-of-the-tongue phenomenon, where a person feels they know something but cannot quite retrieve it. This experience is common when trying to recall a specific name or word that feels just out of reach.
Motivated Forgetting: Psychologist Sigmund Freud proposed that people forget because they push unpleasant or intolerable thoughts and feelings deep into their unconscious. He called this phenomenon repression. Repression occurs when the ego, the part of the mind responsible for balancing conscious awareness with deeper unconscious impulses, actively pushes distressing memories or information out of conscious awareness. According to this theory, memories of traumatic or anxiety-provoking experiences are stored in the unconscious mind, where they are inaccessible to conscious thought in order to prevent overwhelming emotional pain or discomfort.
According to psychodynamic theory, repression is believed to shield an individual from psychological harm by keeping distressing memories of past experiences from entering awareness. However, these repressed memories are not erased; they may still influence behavior and emotions indirectly. The idea that people forget things they don’t want to remember is also called motivated forgetting or psychogenic amnesia.
Although repression is central to Freudian psychodynamic theory, the concept remains controversial, with critics questioning the validity of repressed memories and how accurately they can be recovered. In any case, the idea that people may unconsciously block out distressing information continues to be a significant part of discussions around memory and trauma within psychodynamic perspectives.
Physical Injury or Trauma: Anterograde amnesia is the inability to remember events that occur after an injury or traumatic event. Retrograde amnesia is the inability to remember events that occurred before an injury or traumatic event.
Distortions of Memory
Memories aren’t exact records of events. Instead, memories are reconstructed in many different ways after events happen, which means they can be distorted by several factors. These factors include schemas, source amnesia, the misinformation effect, the hindsight bias, the overconfidence effect, and confabulation.
Schemas
A schema is a mental model of an object or event that includes knowledge as well as beliefs and expectations. Schemas can distort memory.
Example: Suppose a high school junior visits her sister’s college dorm room for the first time. She’s never been to a dorm before, but she’s seen dorms in movies, read about them, and heard her friends talking about them. When she describes the room to another friend after the visit, she comments on how many clothes her sister had and how many huge books were on her sister’s desk. In reality, the books were hidden under the bed, not out in the open. The clothes were something she actually saw, while the books were part of her dorm-room schema.
Source Amnesia
Another reason for distorted memories is that people often don’t accurately remember the origin of information.
Example: After witnessing a car crash on the freeway, Sam later tells friends many details about what he saw. It turns out, however, that there is no way he could have actually seen some of the details he described and that he is, in fact, just reporting details he heard on TV about the accident. He isn’t deliberately lying. He just may not be able to remember where all the different pieces of information came from.
This inaccurate recall of the origin of information is called source amnesia, source misattribution, or source monitoring error.
The Misinformation Effect
The misinformation effect occurs when people’s recollections of events are distorted by information given to them after the event occurred. The psychologist Elizabeth Loftus did influential research on the misinformation effect that showed that memory reconstructions can affect eyewitness testimony.
Example: A bank robber enters a crowded bank in the middle of the day, brandishing a gun. He shoots out the security cameras and terrifies everyone. He is taking money from a teller when one of two security guards approaches the robber, draws his own weapon, and shoots. Suddenly, another shot is fired from a different direction and the security guard falls to the ground, shot. Some of the customers see that the other security guard, who was approaching the robber from the other side, mistakenly shot his partner. Later, police ask the witnesses when the robber shot the guard, and they report that he shot after the guard fired on him. Even though they saw one guard shoot the other, they are swayed by the misinformation given by the police.
In one of Loftus’s early experiments, she showed research subjects a film of a simulated automobile accident at an intersection with a stop sign. Afterward, she told half the subjects that there was a yield sign at the intersection. When asked later to describe the accident, those who had received the misleading suggestion tended to claim with certainty that there was a yield sign at the intersection, while those subjects who received no misleading suggestions had a more accurate recollection.
Constructive Memory
Constructive memory refers to the process by which memories are not simply recorded but actively constructed based on past experiences, expectations, and contextual information. This means that each time a memory is recalled, it can be altered, enhanced, or influenced by new information, which may lead to subtle or even significant changes in its content.
Memory consolidation is the process by which short-term memories become stable and stored as long-term memories. During consolidation, which occurs over hours to years, memories can be influenced by factors such as sleep, emotional experiences, or related information. The brain reorganizes and stabilizes memories by repeatedly “replaying” them, particularly during sleep, and integrating the information with other memories and knowledge. While consolidation helps reinforce memories, it can also alter them over time by blending in elements from other experiences or information encountered after the initial event.
Imagination inflation is a phenomenon that occurs when imagining an event increases confidence that it actually happened, even if it did not. Studies have shown that repeatedly imagining an event can create a false memory, as the brain may integrate imagined details into the memory, thus blurring the line between real and imagined experiences.
For instance, in another well-known study by Elizabeth Loftus, known as the “lost in the mall” study, participants were asked to recall several real childhood events provided by their family members, along with one fabricated event – that they had been lost in a shopping mall as a child. During a series of interviews, participants were asked to recall details about each event, including the false one. In the end, about a quarter of participants reported either partially or fully “remembering” the false event. This study highlighted how suggestion, imagination, and repeated questioning can lead people to “remember” events that never happened. This effect can be especially strong for events that are plausible or similar to past experiences.
