Features of LTM
- holds info for indefinite period of time
- seemingly limitless
- retrieval: process of recovering info from LTM into STM
- info can be lost from LTM
STM vs LTM - same or different?
- if an individual performances normally on Task A, but is impaired on Task B, this is called a dissociation deficit.
- provides evidence to suggest that the two processes are DISTINCTIVE (eg impaired LTM, but normal STM)
The case of H.M.
- had hippocampus removed to prevent epileptic seizures.
- operation cured epilepsy, but left him with amnesia.
- had severe anterograde amnesia: an inability to encode any new memories that occurred AFTER his operation.
- also retrograde amnesia: couldn’t remember much from the period 1-2 years prior to the operation.
- his STM as tested by the digit span task was within normal range
- suggests that LTM and STM are relatively independent - there is a dissociation between LTM and STM
What is a double dissociation? K.F. Example
- as in H.M.’s case, a dissociation between STM and LTM was observed.
- if the opposite is also seen in another individual (impaired STM, but normal LTM), this is called double-dissociation. Stronger evidence of a dissociation…
- K.F. Had a digit span of two items, yet had a functioning LTM
LTM deals with different info in different ways. How can we describe the different types of LTM?
- the type of knowledge that is being stored (procedural/ declarative)
- the way that this knowledge is expressed (implicit /explicit)
Evidence for a dissociation between procedural and declarative LTM
- some individuals with Amnesia like H.M. are unable to remember any new declarative knowledge, yet are capable of learning new procedural knowledge.
- even if they don’t remember doing the task, their learning curves similar to normal participants.
Evidence to suggest a double dissociation between procedural and declarative LTM
- individuals with dementia due to Huntington’s disease…
- remember doing a task repeatedly, but show no improvement in the task over time.
Evidence of a double dissociation between semantic and episodic LTM memories
K.C. - motorbike accident: couldn’t encode new episodic memories but semantic memories largely unaffected.
Italian woman with brain damage: semantic memory impaired (couldn’t recall facts like the meanings of words), but episodic memory not impaired.
Is there evidence that semantic and episodic memories closely connected, despite evidence of double dissociation a?
Yes!
- episodic memories can become semantic memories.
- parts of an episodic memory trace refer to semantic facts
What is pragmatic inference?
- occurs when someone reads a sentence which leads them to expect or believe in something that was not explicitly stated.
- inferences based upon our prior knowledge.
Eg read the sentence: “the new baby STAYED AWAKE all night”
fill in the blank: “the new baby (stayed awake became CRIED) all night”
Why does pragmatic inference occur?
- we don’t actually need to remember all the details of everything we see/hear/read. We can go by the ‘gist’ of the argument.
- the world is quite predictable. This leads us to be able to rely upon inferences and short cuts when encoding info.
- these short cuts can free up the brain for processing other important information.
Does pragmatic inference show that memory is reproductive or reconstructive?
-memory is RECONSTRUCTIVE
-we reconstruct info based upon the original source info plus our prior expectations and knowledge.
Example, AJ - could recall events in incredible detail.
