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Memory And Forgetting

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What is Memory?

Memory is clearly a central process in all aspects of behaviour

It deals with the reproduction of events and experiences of the past.

A person or an animal experiences ease in relearning an activity, which he had learnt previously. Yet forgetting is also a common experience. In fact, a major part of what is learnt is forgotten, and when we are required to remember it we tend to reconstruct the past. For example, we may not remember the complete story of a bad film. However, if a friend asks us to recount it in detail, we do manage to relate a coherent account, because we fill in the ‘gaps’ in our memory.

Memory is an active, dynamic, complex process.

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The scientific study of memory started only with Ebbinghaus who wrote a volume entitled Uber das Gadachtnis (translated as Memory in 1913, after an extensive five year long investigation of the factors and processes of his own memory.

Ebbinghaus invented the nonsense syllables consisting of a vowel between two consonants (such as QAW, XUW, CEW etc.)

Today Ebbinghaus is famous for his material (NSS), method (experimental) and analysis of data (savings). His retention curve is one of the major pioneer attempts in psychology to reduce experimental data to a mathematical form.

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Memory is often viewed as a kind of store-house of knowledge that is constantly modified by experience.

These researchers conceptualize memory as sensory, short term, and long-term memory (Atkinson and Shiffrin, 1971). Alternatively those who think of memory as a dynamic process hold that there are various levels of processing information, and that the deeper the level at which information is processed at the time of encoding, the better our memory for it. They also believe that there are no separate short-term and long-term stores (Craik and Lockhart, 1972).

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Tulving (1972) distinguishes between episodic and semantic memory. Episodic memory refers to knowledge about oneself – what did you have for breakfast, how many brothers and sisters you are, etc. It can be usually dated as to when the information was acquired.

Semantic memory is the general knowledge of the world – who is the president of United States, the importance of Ganga in the Hindu religion, etc.

Tulving (1972) says, “Episodic memory receives and stores information about temporally dated episodes or events, and temporal–spatial relations among these events…Semantic memory is a mental thesaurus, organized knowledge a person possesses about words and other verbal symbols, their meaning and referents, about relations among them, and about rules, formulas, and algorithms for the manipulation of these symbols, concepts, and relations”.

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Another major distinction is between explicit and implicit memory (Schacter, 1987). Explicit memory is memory with awareness. The subject is instructed to remember material for which he is to be tested later on. Traditional experiments in memory that tested recall, recognition, etc. were all experiments in explicit learning. Research in implicit memory started in earnest only in the last two decades of the twentieth century. Implicit memory does not involve explicit or conscious recollection of any previous experience. It is tested by the change on various kinds of memory tasks due to prior experiences outside the awareness of the subject or due to something the subject had not been explicitly instructed to learn for a future test. Though the task instructions do not make an explicit reference to an episode in the subject’s personal history, the performance of the subject is nevertheless influenced by such events.

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Stages of Memory

Memory can be described in terms of three stages: acquisition, storage, and retrieval.

In the acquisition stage, information is encoded into memory. It was felt initially that all experiences are encoded in the brain in the form of a memory trace – the engramIn his book In search of an engram Lashley (1950) mentions that removing specific parts of a rat’s brain affected his behaviour, but did not totally eliminate specific memories. He concluded that if at all they are stored in the brain, memories are distributed throughout the brain. Experimenting on rats, Hyden (1967) found noticeable changes in the amount of RNA in the brain of trained animals and thus recognized that RNA presumably influences cell development. Nerve cell responds by increasing the production of several chemical molecules whenever a wave of electrical activity sweeps the length of the nerve cell.

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The storage stage is the warehousing of the information acquired. Since there is often a difference in the quantity and quality of the information that goes into the store and later comes out of the store, researchers assume that processing of information continues even when it is in storage. A great deal of information may be lost through forgetting, and a great deal may be added through consolidation and reconstruction.

Retrieval refers to the process of bringing information out of memory. There are two basic methods of retrieval. When information is present in the environment, people retrieve it from memory through recognition. But if the information is not present in the environment, they must retrieve it through recall.

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Morgan, King, Weisz, and Schopler (1986), mentioning the stages of memory, say that “it is the encoding, storage, and retrieval of what was learnt earlier”.

Crider, Goethals, and Kavanaugh (1989), adhering to the storage view of memory, hold that “memory is the ability to store information so that it can be used at a later time”.

Morris (1990) holds that “memory is the process by which material is retained”. He conceptualizes memory as a process in line with the information processing approach of the modern researchers in this area. According to Baron (2001) memory is “the capacity to retain and later retrieve information”.

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Sensory Memory

Sensory memory is the memory for all the stimuli impinging upon the organism at any particular time. It is the memory for all the sensations that an organism has at any particular time

Sperling (1960) devised the partial report method to study sensory memory.

only three kinds of sensory memories have been identified and studied by the researchers. Neisser (1967) names them iconic memory (related to vision), echoic (related to audition), and haptic (related to the skin senses).

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iconic memory lasts for only about a second, whereas echoic memory lasts for as long as 4 seconds.

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Characteristic of Sensory Memory

It is very vivid – clear and detailed. Perhaps it contains information about all the stimuli impinging on the sense organs.

It lasts for a very short time. Iconic memory lasts for only about a second whereas echoic memory lasts about four seconds.

It is non – associative in nature. It is neither episodic nor semantic.

Perhaps it processes only ecologically valid stimuli.It may be more implicit than explicit in nature.

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Short Term Memory

Short term memory is that part of the memory structure in which information is stored temporarily.

short-term memory is temporarily active and conscious. It is relatively more permanent than sensory memory, but less enduring than long term memory.

It is also called the working memory, because it contains information that is currently in use by the individual, being acted upon, and in consciousness (Anderson, 1985; Baddeley, 1983).

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Evidence for STM also comes from the serial position effect, the fact that the first few items in a serial task are recalled the best (primacy effect), followed by the last few items (recency effect), and the middle items are recalled the least. The graphical representation of the relationship between a word’s position and its recall is called the serial position curve.

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Atkinson and Shiffrin (1968) hold that the short term memory, in part, consists of buffers, or memory stores, that hold verbal or visual information. A buffer has a relatively limited capacity, and can hold information only for a limited time. Information enters the buffer one item at a time.

Baddeley (1986, 1992) claims that there are at least three components of working memory: the articulatory loop, the visuospatial sketchpad, and the central executive. The articulatory loop is a kind of internal speech mechanism that functions to rehearse verbal information. The visuospatial sketchpad functions to rehearse visual images. Both function independently of each other. The central executive is the skill or process that makes decisions about which other component of working memory must be activated to accomplish a task.

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information is retained in the STM for a very short while. In fact the material is completely lost in about 20 – 30 seconds. Information may be retained in STM if the subject uses maintenance rehearsal, i.e., repeats the cognitive activity on the information again and again.

the information in STM can be transferred to the LTM through elaborative rehearsal that involves a deeper and more thorough analysis of the information.

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Information is stored in STM primarily in acoustic (sound) codes.

Forgetting in STM occurs due to decay as well as interference.

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Characteristics of STM

It lasts for only 20-30 seconds.It has limited storage capacity. It can store / process

only 7+2 chunks of information at any time.Information can be retained in STM indefinitely

through maintenance rehearsal.Information is encoded in STM primarily in acoustic

codes, though other codes may also be used.Retrieval of information from STM is through a serial,

exhaustive search process.Forgetting in STM in due to both decay and

interference.

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Long Term Memory

Information in long-term memory exists indefinitely. There is no time limit in long-term memory.

LTM does not appear to be limited in storage capacity either. It has an unlimited capacity.

Information is acquired into LTM through elaborative rehearsal

A major factor in encoding of information in LTM is activation or arousal. Generally, greater the arousal level better is the memory.

Information in LTM is coded in at least three ways: semantic, visual, and acoustic. Of these, maximum use is made of semantic codes.

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Retrieval of information from the huge warehouse that is LTM is largely with the help of retrieval cues. Retrieval cues prompt people to remember by specifying the goal of memory search, and by directing their generation and evaluation of possible answers.

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There is no time limit in long-term memory. It has an unlimited capacity. Information is acquired into LTM through elaborative rehearsal. Information in LTM is coded in at least three ways: semantic,

visual, and acoustic. Of these, maximum use is made of semantic codes.

The information in LTM is stored in an organized manner. The retrieval of information from LTM depends on retrieval cues

and has to be through a parallel, self-terminating search process. Forgetting occurs due to interference – proactive as well as

retroactive. Interference increases due to similarity of the two tasks, greater amount of learning, etc.

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Short Term Memory Long Term Memory It lasts for only 20-30 seconds. It has limited storage capacity. It can

store / process only 7+2 chunks of information at any time.

Information can be retained in STM indefinitely through maintenance rehearsal.

Information is encoded in STM primarily in acoustic codes, though other codes may also be used.

Little need for organizing information, because it is not a permanent store.

Retrieval of information from STM is through a serial, exhaustive search process.

Forgetting in STM in due to both decay and interference. It lasts for only 20-30 seconds.

• There is no time limit in long-term memory.• It has an unlimited capacity.

 Information is acquired into LTM through elaborative rehearsal.• Information in LTM is coded in at least three

ways: semantic, visual, and acoustic. Of these, maximum use is made of semantic codes.

• The information in LTM is stored in an organized manner.

• The retrieval of information from LTM depends on retrieval cues and has to be through a parallel, self-terminating search process.

• Forgetting occurs due to interference – proactive as well as retroactive. Interference increases due to similarity of the two tasks, greater amount of learning, etc.

STM vs LTM

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Forgetting

Forgetting is the obverse of remembering – a failure to retain what has been acquired.

Retention refers to the amount of original learning that is still effective, while forgetting refers to the amount lost.

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Forgetting Curve

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DECAY THEORY

Decay is a major theory of forgetting. These theorists assume that lapse of time is responsible for forgetting. According to this view, the memory trace deteriorates unless it is used, possibly as a result of the continuous metabolic action of the cells of the nervous system.

the Decay theory holds that a physical memory trace gradually fades as time passes. Like a message drawn in sand and the beach, a physical memory first fades and then disappears altogether.

Forgetting in sensory memory is largely due to decay. The icon disappears within a second, and echoic memory lasts about 4 seconds. Since meaning is not processed, there can be no interference.

Forgetting in STM occurs due to decay as well as interference.

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INTERFERENCE THEORY

Interference theory holds that people forget information because one memory prevents another from being recovered.

Forgetting in STM as well as LTM occurs mainly due to interference – proactive as well as retroactive (also called proactive and retroactive inhibition).

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Proactive Interference Vs Retroactive Interference

Old learning can interfere with the memory of new learning (proactive interference)

New learning can interfere with the memory of old learning (retroactive interference).

Proactive inhibition occurs when information is forgotten because of interference from material that was presented before the learning of the learning task.

Retroactive inhibition occurs when information is forgotten as a result of interference from material that was presented after the learning task.

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