Forgetting Explanation: Displacement.

Forgetting Explanation: Displacement.

1. The displacement theory of forgetting was based on Atkinson and Shiffrin's (1968) multi-store model of memory, which stated that short-term memory had a limited capacity of seven, plus or minus two items.

   • In the late 1960s and early 1970s, the concept of displacement became popular as an explanation for forgetting (Groeger 1997).

2. According to displacement theory, the limited capacity of the short-term memory meant that any extra information would push out, or displace, information already in short-term memory.

   • Information that had been in the short-term store for the longest would be the first to be displaced by new information.
     • Imagine a shelf with seven bottles on it and no room for anymore. If you push another one at one end, the first bottle will fall off at the other end.

3. Studies using free recall of unrelated items tend to show that most people do indeed remember around 7 items of information. Perhaps, once the short-term store is full to capacity, any new items will displace the first items on the list.

   • Displacement can also explain the recency effect in serial position effect studies. The recency effect is where we recall the last few items from the list. These results are consistent with displacement theory in that the last few words on the list have not yet been displaced from short-term memory and so are available for recall.
     • Furthermore, if displacement theory is correct, it should be possible to disrupt the recency effect by giving participants another task, such as simple repetition of a nursery rhyme, after the end of the list of words but before the free recall. The nursery rhyme task would displace the words held in the short-term store and the recency effect would disappear.
       • Studies have demonstrated how the recency effect disappears if other information is presented to participants at the end of the list. E.g. Postman and Phillips (1965) and Glanzer and Cunitz (1966).

4. Evaluation.

   • The theory is consistent with Atkinson and Shiffrin's (1968) model of short-term memory.
   • As Atkinson and Shiffrin's (1968) description of short-term memory gave way to the working memory model, displacement theory became less popular.
   • Displacement is a fairly limited explanation of forgetting as it can only explain forgetting from short-term memory.
   • In studies involving an interference task, forgetting may be due to decay because of the extra time between learning and recall rather than being due to displacement.