Explanations for forgetting
Forgetting is the failure to retrieve memories, with information either no longer in, or unable to be retrieved from, storage. Interference theory sees material becoming confused with, or disrupted by, other information during coding, leading to inaccurate recall. Proactive interference, which works forwards in time, occurs where information previously stored interferes with attempts to recall new information. For example, the memory of your old phone number disrupts attempts to recall your new phone number. Retroactive interference, which works backwards in time, occurs when coding of new information disrupts previously stored information. For example, the memory of your new password prevents recall of your old password. Cue-dependent forgetting sees recall as dependent upon retrieval cues (prompts that facilitate recall). Forgetting occurs if the retrieval cue under which a memory is stored cannot be accessed. Context-dependent failure occurs with external retrieval cues, where forgetting occurs as the external environment is different at recall from how it was at coding. For example, you may perform worse in an exam sat in an unfamiliar room than in the room where you learned the material. State-dependent failure occurs with internal retrieval cues, where forgetting occurs because an individual’s internal environment is dissimilar to that when the information was coded. For example, a person may fail when sober to recall information that was learned when drunk.
Fig 2.4 Street map of Molenberg in Holland
Schmidt et al. (2000) investigated the influence of retroactive interference on the memory of street names learned in childhood. 211 Dutch participants aged 11 to 79 years were given a map of Molenberg, where they had gone to school, with 48 street names replaced with numbers. Participants had to recall as many names as possible. Other relevant details were also collected, such as how many times they had moved house, where they had lived and for how long, how often they visited Molenberg etc. The amount of retroactive interference was assessed by how many times participants had moved to other neighbourhoods (and therefore learned new sets of street names). A positive correlation was found between the number of times participants had moved neighbourhoods outside of Molenberg and the number of street names forgotten. This suggests retroactive interference, as learning new sets of street names makes recalling old sets difficult.
• Peterson & Peterson (1959) gave participants meaningless words of 3 letters and got them to count backwards aloud to prevent rehearsal. After 18 seconds only 5 per cent of participants showed correct recall. This illustrates how memories fade over time, and suggests that forgetting may be due to information no longer being in storage, as well as to retrieval problems.
• Darley et al. (1973) found that participants who had hidden money while they were high on marijuana could not recall where they had put it, but they could when they were high again. This supports the idea that forgetting occurs when internal context of retrieval differs from that of coding, as stated by state-dependent learning.
• Abernethy (1940) found that students recalled information best when in the room they had learned the material in with their usual teacher, rather than in an unfamiliar room with an unfamiliar teacher. This supports the idea of forgetting occurring when external context of retrieval differs from that of coding, as stated by context-dependent failure.
Schmidt et al.’s (2000) street name study is especially useful, as it involves a real-life scenario and therefore has high external validity.
Schmidt et al.’s methodology can also quite easily be adapted to assess the effect of proactive, as well as retroactive, interference.
Cue-dependent theory is regarded as the best explanation of forgetting in LTM, due to the huge amount of supportive research the explanation has, which shows the importance of retrieval cues in facilitating accurate recall.
There are a number of extraneous variables in Schmidt et al.’s (2000) study. For example, participants who played a lot in the streets of Molenberg as children, or who walked to school, may have learned street names to a greater extent and therefore would have had better recall than those who did not play in the streets or went to school by car.
Interference theory only explains forgetting when 2 sets of information are similar, like simultaneously learning 2 languages at school. This does not happen that often and so cannot explain the majority of forgetting.
Although studies show interference to be a real effect, they do not identify the cognitive processes at work, which means the explanation is incomplete.
One practical application of the interference explanation of forgetting is that, wherever possible, in order to cut down on retrieval failures, students should sit an exam in the room where they learned the material, so that the context of retrieval is the same as that of coding.