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Unlock This CourseThe Multistore Model, proposed by Atkinson and Shiffrin in 1968, is one of the most influential theories explaining how human memory works. It suggests that memory consists of three separate stores: sensory register, short-term memory (STM) and long-term memory (LTM). Information flows through these stores in a linear fashion and forgetting can occur at each stage through different processes.
Key Definitions:
The Multistore Model identifies three distinct memory stores: the sensory register (holds information for milliseconds), short-term memory (holds 7±2 items for 15-30 seconds) and long-term memory (unlimited capacity and duration). Information must pass through each store sequentially to reach long-term storage.
Displacement is a key explanation for forgetting in short-term memory. According to the Multistore Model, STM has a very limited capacity - George Miller famously suggested we can hold 7±2 items (between 5-9 pieces of information) at any one time. When this capacity is exceeded, new information literally pushes out or displaces older information.
Think of short-term memory like a small car park with only seven spaces. When all spaces are full and a new car arrives, one of the existing cars must leave to make room. In memory terms, when STM reaches capacity and new information enters, the oldest or weakest information is displaced and lost forever unless it has been transferred to long-term memory through rehearsal.
STM can only hold 7±2 items simultaneously. This creates a bottleneck where information competes for limited space.
Generally, the oldest information in STM is displaced first when new information enters, following a queue-like system.
Once displaced, information cannot be recovered unless it was previously transferred to long-term memory.
This classic study demonstrated displacement in STM. Participants were given three-letter combinations (like XQF) to remember, then asked to count backwards in threes to prevent rehearsal. Results showed that after 18 seconds, participants could only recall about 10% of the letters, supporting the idea that without rehearsal, information is quickly displaced from STM by the counting task.
Decay theory suggests that forgetting occurs because memory traces naturally fade over time when they are not used or rehearsed. Unlike displacement, which is about competition for space, decay is about the deterioration of memory traces due to the passage of time alone.
When we form memories, they create physical changes in the brain called memory traces or engrams. According to decay theory, these traces gradually weaken and fade if they are not strengthened through use or rehearsal. It's like a path through a field - if nobody walks on it, grass grows over it and it eventually disappears.
Decay theory proposes that the simple passage of time causes memory traces to weaken and eventually disappear. This happens automatically, regardless of whether new information is learned.
Both displacement and decay have been studied extensively, with mixed results that highlight the complexity of human memory and forgetting.
Several studies support the displacement explanation of forgetting in STM:
Murdock found that in word lists, middle items are forgotten most (displaced by items before and after), while first and last items are remembered better.
Research consistently shows that when people try to remember more than 7±2 digits, earlier digits are forgotten as new ones are added.
Students often forget earlier information when teachers present too much new material at once, supporting displacement theory.
These researchers used a probe digit technique where participants heard lists of numbers and had to recall the digit that came after a specific 'probe' digit. They found that forgetting was mainly due to the number of items that followed (displacement) rather than the time that passed (decay), providing strong evidence for displacement over decay in STM.
While displacement has strong support, some evidence also supports decay theory:
Research shows that memories can fade during sleep when no new information is being processed, suggesting that time alone can cause forgetting through decay processes.
Both displacement and decay theories have important strengths and limitations that affect their usefulness in explaining forgetting.
Displacement theory has several advantages as an explanation of forgetting:
However, both theories face significant challenges:
The Multistore Model may oversimplify memory by treating it as separate stores rather than interconnected processes.
Much research uses artificial tasks that may not reflect how memory works in real-life situations.
Other factors like interference, lack of attention, or poor encoding may better explain some forgetting.
Understanding displacement and decay has practical implications for education, work and daily life.
When revising, students often experience displacement when trying to cram too much information at once. The last topics studied may displace earlier ones from STM. To combat this, effective study strategies include: breaking information into smaller chunks, regular review to prevent decay and using rehearsal techniques to transfer important information to long-term memory.
Teachers can use knowledge of displacement and decay to improve learning: