Features of Memory

• 1.Duration= how long memory lasts
• 2.Capacity= how much information memory can hold
• 3.Capacity= how it is stored (the way in which information is represented, eg visual, auditory).
• Sperling 1960- Sensory:

  • Exposed PPs to 3 rows of 4 letters for 50 milliseconds
  • They remembered 4-5 on average but knew there had to be more than that.
  • PPs trained to use tones for which line to recall (tone was played after exposure).
  • PPs remembered average of 3 items, which means at this stage they would've been able to remember 3 from any row as the image was still available in the sensory memory.
  • Shows duration to be extremely brief fractions of a second- as the information decays & disappears so rapidly.
  • Is reliable as can be repeated with similar results, but lacks validity.
• Peterson & Peterson- STM Duration:

  • Used nonsense trigrams, eg SPG365 & PPs had to count back in 3s or 4s for a duration of either 3,6,9,12,15,18 seconds.
  • Found that 90% could recall the trigram after 3 seconds, compared to 2% after 18 seconds- showed duration of STM was 18-30 seconds.
  • Easy to replicate, clear results (reliable), but lacks ecological validity (artificial) & lacks mundane realism.
  • Displacement may be a better explanation: new incoming information (counting) was simply displacing old information.
• Jacobs- STM Capacity: 1

  • PPs were read lists of letters or numbers that they had to recall immediately after presentation.
  • Jacobs gradually increased the length of these digits/ letters until the PP could only accurately recall the information in the correct order on 50% of occasions. Recall had to be in the correct order.
  • Difference found between capacity for numbers & letters; PPs could recall 9 numbers & 7 letters, & noticed recall seemed to increase with age.
  • STM has a capacity of between 5 & 9 items of info & as age increases, we appear to develop better strategies of recall.
• Jacobs- STM Capacity: 2

  • Miller & others have also discovered that chunking can increase capacity (BBC or 01858 becomes 1 chunk of info rather than 3 or 5 distinct chunks)- supports Jacobs' theory.
  • Lacks ecological validity; memory being used for artificial task.
  • Research is replicable; later studies have supported Jacobs' findings.
• Bahrick- LTM:

  • 392 high school graduates asked to remember former classmates, eg recalling names, recalling names from pics or matching names to pics.
  • PPs recalled remarkably well on recognition rather than recall- 48 years on still had 70% accuracy, but dip in performance after 48 years.
  • Shows that duration of LTM is unlimited.
  • Has good ecological validity as testing recall memories & good sample size so can be generalised to a wider population.
  • Difficult to generalise results to entire population as graduates used bias- no clear conclusions drawn to explain dip in performance.
• Baddeley et al- Coding in STM & LTM: 1

  • PPs presented either: acoustically similar words (map, mad, cat, cap), acoustically dissimilar (pen, cow, day), semantically- meaning- similar (tall, high, broad, wide) or semantically dissimilar (foul, thin, safe).
  • STM- presented 5 words & recalled immediately, if sounded similar it was more difficult- concluded that STM must be acoustic.
  • LTM- presented 10 words 4 times, after 20 mins PPS recalled, & acoustically similar had no effect, but they performed worse with words similar in meaning- concluded that LTM is semantic.
• Baddeley et al- Coding in STM & LTM: 2

  • STM= acoustic & LTM= semantic
  • Clear results, high internal validity, easy to replicate, so reliable.
  • Lacks ecological validity (artificial) & lacks mundane realism, demand characteristics involved & questioned whether waiting 20 mins is really testing LTM.
  • There's lots of evidence suggesting different types of coding for both STM & LTM, so conclusion is actually inaccurate & memory is coded according to circumstance in which it was formed, rather than where it is stored.
• STM:

  • Coding= acoustic
  • Capacity= 7+-2 (5-9)
  • Duration= 18-30 seconds
• LTM:

  • Coding= semantic
  • Capacity= unlimited
  • Duration= unlimited
• Sensory Register:

  • Coding= multi-codal
  • Capacity= limitless
  • Duration= fractions of a second