Long Term Memory

Long Term Memory

1. Houses what we typically consider to be our 'memory'

2. Stored material can be retrieved from LTM into working memory/STM for recall

3. LTM is virtually limitless in capacity and duration, limited only by encoding and retrieval

   • Encoding is the process through which info is put into LTM
   • Though maintenance rehearsal can keep things in STM, it is not particularly effective for getting info into LTM
   • Elaborative rehearsal makes the info more meaningful and more likely to be encoded into LTM

4. Depth of Processing

   • Craik and Lockheart proposed that deeper, more meaningful types of info processing lead to greater retention of info than more shallow forms of processing
   • Self-reference Effect
     • One of the ways you can process info more deeply is to think about how it relates to you, you remember more info if you try to relate the info to yourself
   • Rogers et al. asked participants to remember lists of words by focussing on a particular kind of characteristic
     • 1.Visual, 2.Acoustic, 3.Semantic, 4.Self-reference
     • Recall was poor for shallow processing (1, 2), better for meaning processing, and best for self-referential processing

5. Encoding Specificity

   • Recall is better when the retrieval context is similar to the encoding context
   • Forgetting is more likely to occur when encoding and retrieval contexts do not match
   • Marian and Fausey's research on bilingual English/Spanish speakers supports encoding specificity
     • Participants listened to 4 stories, 2 in English, 2 in Spanish, after a short delay participants were asked questions about each story, half in the language it was originally presented and half in the other language
     • Participants were 15-18% more accurate when answering questions in the same language in which the story was originally presented
   • Tulving has conducted numerous experiments showing the effects of encoding specificity using the recall paradigm
     • Participants were given a list of words including an ambiguous term (e.g., 'jam'), half the participants are primed to a certain interpretation of 'jam' by surrounding it with prime words in the list, (e.g., fruit, toast, spread), after a short delay memory is tested by presenting participants with a series of items and asking if they were on the list
     • 'Jam' is presented, but in the context of 'traffic jam', people typically report that 'jam' was not present even though their memory for the rest of the list is good

6. Consolidation

   • New memories appear to be initially "stored" in the hippocampus, and are then slowly transferred (consolidated) across the neo cortex (i.e., you do not have a "memory gyrus")
   • Memory consolidation commences whilst you are awake, but seems to work particularly efficiently when you are asleep
   • We now believe that consolidation occurs during NREM sleep

7. Implicit Memory

   • The system underlying unconscious memories
   • Implicit memory is split into two forms
     • Perceptual Representation
       • Represents info about the form and structure of words/objects but does not contain semantic info
       • Perceptual Priming: Phenomenon in which a degraded stimulus is processed better if it has been previously processed in non-degraded form
         • Works for visual imagery and verbal stimuli
     • Procedural Memory
       • Learned skills that are challenging to describe, there is no conscious retrieval
       • Your procedural memory is triggered when appropriate cues are present
   • Implicit memory allows you to type without looking at the keyboard, yet you would be unlikely to be able to recall it explicitly
     • Snyder et al. found that on average, skilled typists correctly located only 14.9 letters (57.3%) in a free recall task
   • This difference between implicit and explicit memory sometimes help police learn the identity of missing persons suffering amnesia
     • Asking a person to automatically dial a number on a phone allows implicit memory to take over

8. Explicit Memory

   • The system underlying conscious memory
   • Episodic Memory
     • Memory of your personal history
   • Semantic Memory
     • Your general knowledge
   • Spiers et al. conducted a meta-analysis of 147 cases of amnesia subsequent to hippocampal or fornix damage
     • Episodic memory was impaired in all 147 cases
     • Semantic memory was impaired in many, but not all cases
     • Results suggest that in people with amnesia, episodic memory is more vulnerable to loss than semantic memory
   • Vargha-Khadem et al. reported 2 patients showing the opposing pattern of performance, confirming the dissociation between episodic and semantic memory
     • Patients Beth and John suffered bilateral hippocampal damage prior to age 4, both exhibited poor episodic memory for daily events, but attended normal schools
     • Both show poor episodic memory, but intact semantic memory, this led to patients having difficulty 1. Spatially (where?), 2. Temporally (when?), 3. Episodically (what?)
   • Tulving reported patient KC who, following brain injury, was unable to recall any personally experienced events prior to the accident (retrograde amnesia), however, semantic knowledge was relatively unaffected
   • Yasuda et al., reported a patient who exhibited relatively intact recall for personal experiences in the period prior to the onset of amnesia (retrograde amnesia)
     • Had a severe deficit for the recall of semantic knowledge from before her amnesia

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