Exploring Models of Memory and Amnesia

1. BHS 499-07Memory and Amnesia Models of Memory

2. Plato’s Model • Plato extended the wax tablet metaphor to refer to birds in an aviary. • Birds are located in specific places. • Search processes are needed to hunt for them. • William James referred to primary and secondary memory. • New experiences linger briefly and need not be stored forever (secondary memory).

3. The Modal (Multi-Store) Model of Memory • Modal refers to sensory modality (way of receiving info from outside world). • Heuristic means “rule of thumb” – this theory of stages is a way of thinking about memory not to be taken literally. • This multistore (modal) model was the guiding framework for decades.

5. Multiple Memory Systems • Memory is not unitary but consists of several subcomponents (parts). • Atkinson & Shifrin: • Sensory store, short term, long term stores • Tulving’s Triarchic Theory: • Episodic Autonoetic (self) • Semantic Noetic (formal knowledge) • Procedural Anoetic (automatic skills)

6. Other Classifications • Declarative vs Nondeclarative • Declarative includes episodic and semantic memory • Nondeclarative includes procedural memory, classical conditioning and priming • Explicit vs implicit • Explicit memory involves consciousness, implicit does not.

8. Beyond Multi-store Models • Levels of processing theory (Craik & Tulving) – it isn’t where memories are processed that matters, but how. • Shallow vs deep processing • Elaborative rehearsal vs repetitive rehearsal • Short term memory was replaced by Baddeley’s model of the central executive (where rehearsal takes place).

9. Current Issues • Neurological bases for memory • Impact and importance of emotion on memory • Use of multiple memory sources (fuzzy trace theories) • Embodied cognition – how our grounding in the world influences memory

10. Sensory Memory • Three sensory registers discussed by Radvansky and Parkin texts: • Visual sensory register (iconic memory) • Auditory sensory register (echoic memory) • Touch sensory register (haptic memory) • Briefest duration -- < 5 sec • Retains characteristics of the stimulus so that meaning can be interpreted

11. Iconic Memory • How many items, how long does it last? • It is difficult to study the capacity of iconic memory because items fade before people can report them aloud. • Averbach found that increased presentation time did not improve memory for dots. • Sperling’s partial report procedure showed that an entire array was remembered well, but only for ~.250 seconds, ¼ sec.

12. Increasing the duration of the stimulus increases the dots remembered up to 6, but not much after that.

13. Sperling’s partial report procedure showed greater recall when a tone cued people to look at a specific line immediately after viewing the stimulus, but not after a delay.

14. Anorthoscopic Perception • Images in the iconic register are combined to form a single mental representation. • Anorthoscopic perception (seeing more than is there) – an image is passed through a slit at 250-300 ms (quickly). • The original icon is compressed to build up the entire representation – so not an after image but a constructive process.

15. The longer a stimulus is viewed, the closer the response is to the actual stimulus (see Actual and 2110 ms)

16. Trans-Saccadic Memory • Saccade – an eye movement (~ 30 ms). • Our eyes are constantly moving over the objects in the world. • Fixation – when eyes stop on a point (typically ~ 300 ms). • A trans-saccadic memory is needed to build-up a mental representation from all of the eye movements

17. Subjects were unable to make the necessary comparisons in either of these two tasks, so there must exist a trans-saccadic memory store.

18. Change Blindness • Visual memory is not always accurate. • Movies frequently contain errors of detail that go unnoticed – continuity errors • Only 33% of subjects noticed the change of an actor of the same ethnicity & gender. • Top-down expectations affect what is noticed. • Students notice students not construction workers, or changes that belong in a scene.

19. Echoic Memory • Echoic memory lasts briefly to permit a mental representation to be formed. • More exists in memory than can be reported. • Retention of info is longer (~ 4 sec). • Because sounds can only be heard once, info is kept available longer. • Flow of speech is constructed from a series of passing sounds.

21. Haptic Memory • Less studied. • Air jets were used in a whole/partial report procedure. • Duration was ~ 1.3 seconds.

22. Short Term Memory • Dispute – is short term memory qualitatively different from long-term memory? • Or is it just the part of long term memory that is currently active? • Severely limited in capacity (unlike sensory registers). • Miller’s magic number of 7 +/- 2 (or 4 +/- 1).

23. Chunking • We are capable of thinking about more by forming units out of smaller pieces of information. • The number of chunks is the same as the number of units that can be remembered. • Prior knowledge guides the chunking process. • Race lengths, chess games are large chunks

24. S.F.’s digit span improved with practice as he learned to chunk digits in terms of race results.

25. Duration of STM • Without active attention, info is forgotten in ~ 30 sec (some sources say 15) • How do you tell people not to think about something so you can test it? • Is forgetting due to decay or interference? • Decay -- passage of time erases trace. • Interference – new info displaces the old

26. This task tests for interference. This task tests for delay.

27. STM Retrieval • Does retrieval involve a serial or a parallel search? • Sternberg’s paradigm of digits followed by a probe showed serial exhaustive search. • Most people find this result surprising, showing why self-report may be flawed. • An alternative explanation is parallel search with limited resources (requiring more time). • Most likely both processes are involved.

28. Serial Position Curves • Position in a list of items affects likelihood of being recalled. • Primacy effect – items at the beginning of a list are remembered better. • Due to encoding in long term memory via more rehearsal. • Recency effect – items at the end of the list are remembered well because still active in short term memory.

32. Modifying Serial Position Effects • Placing an irrelevant item at the end of a list eliminates the recency effect. • Memory for actions is different – no primacy effect because the focus is on individual actions so less rehearsal. • Suffix effect – recency effect is diminished when new info is added at the end (the more the greater the effect).

34. Memory for Order of Items • The position of the item must be remembered, not the item itself. • Slot-based models – info is dropped into a series of slots, read off in order. • Chaining models – associative links form a chain (but items can be skipped). • Perturbation model – hierarchy of chunks is disturbed.

35. More Serial Order Models • Inhibition models – retrieval starts with the most active, then inhibits it and goes to the second most active, and so on… • Inhibition prevents things just recalled from being recalled again immediately. • Repetition blindness – people fail to see the same word presented soon after it was first seen on a screen. • Context-based models – order tied to context.