Short Term Memory

1. Short Term Memory • William James (1900): Made Primary-Secondary memory distinction. Important distinction: Primary was limited capacity and duration. Secondary more permanent. • George Miller: Magical #7 (1956). Emphasized the importance of recoding or chunking of information. • Brown-Peterson task: test of duration of STM Trigram: KNP; 517; backwards by 3 from number for variable amount of time, by 15-18 seconds trigram gone

2. Decay or Interference? • Brown-Peterson studies suggest that it might be delay that leads to loss in STM • Waugh and Norman disagreed, argued that verbal repetition of numbers may have constituted interference effects. • Waugh/Norman (1965) study: decay vs. interference. List of numbers presented: 7 9 5 1 2 9 3 8 6 4 3 7 2 (tone) Tone marks repeated number; must recall number coming after repeated number first time (answer: 9) Two variables: rate of presentation: (1/sec; 4/sec) Number of intervening items (1-13) If decay then rate should be critical If interference then number of items No effect of rate; significant effect of items. Conclusion: Far stronger effect of interference than decay Two forms of interference: Retroactive: newer blocks older (present in WN study) Proactive: older blocks newer

3. Wickens Release from PI: forgetting due to build up of semantic proactive interference items– distracter-recall; same category items -distracter-recall; same category items distracter-recall; then switch (for experimental group).

4. STM/LTM distinction: Serial Order Effect Primacy: rehearsal allows for encoding into LTM Recency: still present in STM Delay before recall affects recency but not primacy part of the effect

5. Searching STM: Sternberg Paradigm Sternberg Task Search set (1-6 items); Comparison item; yes/no part of set? Ex: K X G D (G=yes) (F=no) RT’s increase linearly with set size; RT for yes and no equal. Serial/Exhaustive search.

6. Baddeley’s Model of Working memory PL: phonological store + articulatory loop Articulatory suppression effect: talking suppresses memory Phono similarity effect: similar sounding words harder to remember than dissimilar Brain anatomy of WM: Dorsolateral Pre-frontal Cortex: CE Broca’s area and left parietal: PL Occipital and posterior parietal: VSSP

7. VSSP: Mental rotation studies Farther apart pairs are from similar orientation the longer the reaction time. Longer rotations take more time

8. Episodic buffer: putting it all together • EB: binds info from other systems together to form meaningful memories. • Dual task robs resources from non-meaningful processing not meaningful • Jefferies, Lambdon, Ralph and Baddeley (2004) • Subs learned unrelated words or sentences or meaningful sentences that formed a story • When secondary task applied (monitoring computer screen for form), performance on non-meaningful conditions declined, but not on meaningful sentence condition • Ability of EB to use meaning for bind memories allowed for excess resources in meaningful sentence condition, but resources in non-meaningful conditions all used up trying to recode word/sentences.

9. Selective interference: Dual task studies in WM • Rationale: if PL and VSSP are truly separate systems then loading two tasks into one should cause a greater decrement in performance than spreading two tasks across two systems (one in each). • Task 1: either letter span (PL) or image span (VSSP) • Task 2: either adding (PL) or imaging (VSSP)

10. Measuring WM capacity: WM span Requires both processing and storage Ex: 6x2-2=10? SPOT 5x3-2=12? TRAIL 3x2-4=2? BRAND Correct response: y,n,y SPOT, TRAIL, BRAND WMS=3 Increased WMS associated with: Less distractibility: less likely to hear name in unattended channel in dichotic listening test Better filtering of irrelevant details when processing text More consistent responses on moral reasoning tests (consistent moral principle applied across different dilemmas for high span subjects) Word fluency: better able to retrieve category-relevant words from memory