Inf1-CG Memory 3: Recall, semantic memory, and forgetting

Alyssa Alcorn
Henry S. Thompson
15 October 2010
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1. Retrieving information

Retrieval is the process of using cues (any modality) to recover a target memory

It may be necessary to follow an associative chain of cues to the target memory

Be aware that "remembering" a memory is not like opening a file stored on your hard drive

Three large and very important differences are:

  1. Memories, especially episodic (event) memories, are changed by the process of retrieval
  2. Human memory is content-addressable rather than storing items at a fixed address, as does a computer
  3. Items stored in long-term memory tend to decay over time (one form of forgetting)

2. Recall

Recall is when a person must generate items from memory

This is effectively a search process. Examples include:

Free recall tasks (in which participants can recall items in any order) show several sequencing effects:

3. Concepts, semantic information, and the internet

Google and the Mind (2008) is an example of using tools from Informatics to study behaviour

This paper is strongly influenced by Anderson’s rational analysis

Research question: do human memory and internet search engines use similar solutions to retrieve information in response to some query?

This lecture introduces some main concepts for this paper, it will be discussed in more depth for the tutorial

4. The internet, semantic memory, and semantic networks

The authors describe several assumed parallels between connected web pages on the internet and information stored in human memory.

5. Semantic memory, cont'd

Possible to link concept-nodes in a network based on their semantic relatedness (similarity to one another)

Relatedness measures "How much does concept 1 have to do with concept 2?"

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In this diagram, the length of the link between two nodes measures relatedness

6. Associative frequency and the PageRank algorithm

PageRank is a more advanced version of the concept of associative frequency

Two key ideas about the PageRank algorithm:

7. What kind of memory is being studied in this paper?

This paper is interested in human word fluency, a type of cued recall

The paper reports an experiment to find out...

In rational analysis terms, this is comparing an optimisation function (the algorithm) to behavioural data

8. Introduction to probability, for understanding “Google and the Mind”

We only briefly discusses probability theory

A traditional frequentist interpretation of probability is interested in counting repeated outcomes from identical "experiments"

But how can one calculate more complex probabilities, such as in a model of an environment?

Probability theory is a major tool used in the Google memory model to make predictions about events

This paper, and many others, are interested in non-frequentist probabilities

9. Probability, uncertainty, and information processing

One of the major functions of the brain as an information-processing system is to infer new information from existing information

A Bayesian interpretation of probability such as the one used in the Google paper is interested in describing degrees of certainty (belief) about various outcomes

Warning! Extremely simplified explanation follows

In the Google paper, one form of prediction would be the probability of producing a particular word as a response in a fluency task

10. Conclusions from Google and the Mind

This has been a very brief introduction to some concepts in this paper, in order to illustrate an application of rational analysis and a novel way of studying human memory

The tutorial will look at this paper in more depth:

You will need to prepare for this tutorial in advance

Again, do not worry about the maths-heavy parts of this paper. Try reading them, but focus on the rest of the paper. You are not expected to learn probability maths in this class

11. Why do we sometimes fail to retrieve information?

Forgetting can be conceptualised as a failure of memory retrieval

Forgetting or retrieval failure can be divided into two categories:

In all of these forms, losing information or failing to retrieve it is a form of optimisation for the memory system

12. Patterns of forgetting: The Ebbinghaus curve

A fundamental rule for most organisms: forgetting increases as time progresses

In one of the earliest psychological studies (still cited to this day) Hermann Ebbinghaus (1885/ trans. 1913) used himself as a participant to study memory for nonsense syllables over time

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His results show that forgetting is not linear, but close to a logarithmic curve

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13. Applying Ebbinghaus’s research

In a long-term example with more naturalistic stimuli, Bahrick (1984) tested retention for foreign language grammar, reading comprehension, recall and recognition vocabulary

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Memory showed exponential decline in retention for first 3-6 years, then stabilisation for up to 30 years

Apparently there is some level of memory “permastore” affected by original training, but not by subsequent rehearsal

14. References

Course texts

Optional reading

Other resources, available through the library or Google Scholar