Human Memory

Human Memory

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Human Memory •

Memory is central to all cognitive function and to all human behaviors. It is the process that follows the perception of current information for later use.

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Many psychologists agree with the dominant theory stating that there are at least two memory systems: SHORT TERM MEMORY (STM), and LONG TERM MEMORY (LTM).

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These are also preceded by an initial stage of sensory memory.

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According to this theory, information must passed first through STM, in which information is held for fairly short intervals, and then get to the LTM in which information is stored for much longer time.

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Within each of the two main systems (STM & LTM) information is to be processed through several stages including encoding, storing, and retrieval. So any act in remembering implies success in these three phases

MODELS OF MEMORY •

So the most accepted model states that there are three stages of memory storage: SENSORY STORE, SHORT-TERM STORE, and LONG-TERM STORE.

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SENSORY MEMORY

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sensory store retains the sensory image for only a small part of a second, just long enough to develop a perception.

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Iconic memory for visual stimuli,

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Echoic memory for aural stimuli

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Haptic memory for touch.

PROCESSES OF MEMORY •

Human memory, like memory in a computer, allows us to store information for later use. In order to do this, however, both the computer and we need to master three processes involved in memory.

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The first is called ENCODING; the process we use to transform information so that it can be stores. For a computer this means transferring data into 1’s and 0’s. For us, it

Human Memory

means transforming the data into a meaningful form such as an association with an existing memory, an image, or a sound. •

Next is the actual STORAGE, which simply means holding onto the information. For this to take place, the computer must physically write the 1’ and 0’s onto the hard drive. It is very similar for us because it means that a physiological change must occur for the memory to be stored.

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The final process is called RETREIVAL, which is bringing the memory out of storage and reversing the process of encoding. In other words, return the information to a form similar to what we stored.

SHORT TERM MEMORY •

1) Different terms are used to refer to STM, but each with its connotation. IMMEDIATE MEMORY, & WORKING MEMORY.

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2) Immediate Memory: This could be considered as the first stage of STM, temporarily holds information retained from the registration process.

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3) When the term working memory is used for this system, it’s mainly used to consider it as a central processing unit of information.

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SHORT-TERM MEMORY (STM) takes over when the information in our sensory memory is transferred to our consciousness or our awareness).

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This is the information that is currently active such as reading this page, talking to a friend, or writing a paper.

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Short term memory can definitely last longer than sensory memory (up to 30 seconds or so), but it still has a very limited capacity.

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According to research, we can remember approximately 5 to 9 (7 +/- 2) bits of information in our short term memory at any given time (Miller, 1956)

Process in STM •

1) ENCODING: Information in STM tends to be encoded acoustically. Although we can use visual code, we prefer the acoustic one. E.g. phone number

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2) We favour the verbal acoustic coding when we try to keep information active by Rehearsing it, i.e., by repeating over and over to ourselves.

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Human Memory

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During STM encoding, the brain organizes information into CHUNKS (the largest possible cluster it can recognize as a familiar pattern).

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3) STORAGE: Perhaps the most striking fact about STM is that it has a very limited capacity.

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On the average, the limit is (7+_ 2). There are however, some individual differences, probably due to long term memory or the use of chunking.

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4) FORGETTING: When the limits of STM is reached, a form of forgetting occurs:

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a)

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b) The other major cause of forgetting in STM is that information DECAYS with time.

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So storage failure when exceeding the capacity.

A new item can enter STM only by DISPLACING an old one.

PROCESSES IN LTM •

1) ENCODING: information in LTM is encoded SEMANTICALLY, that is to its meaning.

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2) STORAGE: the process of storing information as LTM (CONSOLIDATION) may occur quickly or continue for consolidation time. If the item to be remembered are meaningful but the connection between them are not, memory can be improved by adding meaningful connections. This is called ELABORATION..:

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Maintenance Elaboration

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Semantic Elaboration

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Capacity of LTM store: unlimited

Forgetting in LTM •

Many cases of forgetting in LTM are due to Retrieval Failure; that is, the information is there but cannot be found.

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Retrieval failure is more likely to occur when there is INTERFERENCE from items associated with the same retrieval cues.

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Retrieval failure is less likely to occur when the items are organized during encoding and when the context at retrieval is similar to that at encoding.

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Retrieval process can also be disrupted by Emotional Factors.

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Human Memory

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Some forgetting from LTM is due to loss from storage, particularly when there is a disruption of the process that consolidate new memories. Consolidation takes place in the hippocampus and the amygdala. Recent research suggests that consolidation may take a matter of few weeks

FORGETTING •

Ineffective initial encoding, usually occurs because of ineffective attention in the acquisition phase

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DECAY: forgetting occurs because memory fades with time.

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INTERFERENCE: forgetting occurs because of competition from other information –

Retroactive Interference: new information interferes with what has already been learned

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Proactive Interference: old information interferes with what is being learned

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RETRIEVAL FAILURE: sometimes we can not remember something which at another time we can remember it; perhaps this is because of the context cues or retrieval cues present at the time

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motivated forgetting: we may tend to forget things that we do not wish to remember (Freud) (Repressed Memories )

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BRAIN INJURY: –

ANTEROGRADE AMNESIA (injury prevents new memories from occurring):

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RETROGRADE AMNESIA: (injury prevents old memories from occurring)

RECALL AND RECOGNITION •

There are two types of information retrieval: recall and recognition.

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In recall, the information is reproduced from memory.

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In recognition the presentation of the information provides the knowledge that the information has been seen before.

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Recognition is of lesser complexity, as the information is provided as a cue.

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However, the recall can be assisted by the provision of retrieval cues which enable the subject to quickly access the information in memory

OTHER CLASSIFICATION OF LTM

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Human Memory

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Long-term memory

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Long-term memory is intended for storage of information over a long time. Information from the working memory is transferred to it after a few seconds. Unlike in working memory, there is little decay.

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There are two types of long-term memory: episodic memory and semantic memory.

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Episodic memory represents our memory of events and experiences in a serial form. It is from this memory that we can reconstruct the actual events that took place at a given point in our lives.

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Semantic memory, on the other end, is a structured record of facts, concepts and skills that we have acquired. The information in semantic memory is derived from that in our own episodic memory, such that we can learn new facts or concepts from our experiences.

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Explicit memory refers to the kinds of memory manifested in recall or recognition. when we consciously recollect the past.

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Implicit memory refers to the kind of memory that manifest itself as an improvement on some perceptual, motor, or cognitive tasks with no conscious recollection of the experience that led to the improvement. Amnesic deficits concern explicit but not implicit memory.

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Explicit memory breaks with Amnesia, while implicit memory doesn’t. This suggests two separate systems of storage.

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Procedural knowledge (implicit memory) refers to KNOWING HOW. How to drive a car.

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Declarative Knowledge (explicit memory) is related to “KNOWING THAT”: for example knowing that cars run on gasoline.

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