Memory studies

Memory studies

1. Sperling (1960) - Sensory register, capacity and duration

   • Aims - to find out if we store an image of the visual world before it's discarded from memory.
     • Procedure: Pps were presented with a number of 3x4 grids, each containing random letters for 50ms. Condition 1- they were asked to recall the letters. Condition 2 - they were asked to recall 1 of the rows.
       • Findings: Condition 1 - pps only recal 4/5 letters. Condition 2 - recall very good, suggested iconic memory could hold 9/10 items.
         • Conclusions: that the capacity of the SR is larger than 4/5 letters, that the duration is very limited, about 0.5 secs.

2. Jacobs (1887) - STM, capacity

   • Aims - How much info can be held in the STM
     • Procedure: Pps presented with sequence of digits/letters and had to repeat them in same order. Pace was controlled using metronome. Longest correct list was recorded & apps digit span.
       • Findings: pps recalled more digits (average 9.3) than letters (7.3). Capacity increased with age - 8 y/o's remembered 6.6 digits, whereas 19 y/o's remembered 8.6.
         • Conclusions: that people can hold about 7 (+/-2) items in STM, and as age increases we appear to develop better strategies of recall.

3. Peterson and Peterson (1959) - STM, duration

   • Aims - How long simple info stays in the short and long term memory.
     • Procedures: Pps saw a trigram (3 consonants). Asked to recall each one after a delay of seconds: 3,6,9,12,15,18, during which they had to perform an interference task (count backwards from a random 3 digit number in 3s).
       • Findings: The longer the time delay, the more forgetting occurred. After 3 secs, 90% of trigrams were recalled, but after 18 secs, only 5% were.
         • Conclusions: That info is lost rapidly from the STM when there is no opportunity for repetition (lasts for little longer than 18 seconds).

4. Baddeley (1966) - STM & LTM, coding

   • Aims - To investigate the coding of the short and long term memory stores.
     • Procedures: Pps were divided into groups and given different lists of words to learn: acoustically similar/dissimilar, semantically similar/dissimilar. Pps then had to recall the words in the correct order immediately after (STM condition) or 20 minutes later (LTM condition)
       • Findings: STM - recall of acoustically similar lists was poor, ~10%. Acoustically dissimilar lists were recalled the best, ~60-80%. LTM - recall of semantically similar lists were the worst ~ 55%. Recall for other lists was much better ~ 70-85%. Acoustically dissimilar words were recalled the best.
         • Conclusions: STM - that the STM doesn't get muddled based on the sound of words, and it relies on acoustic coding. LTM - there must be some semantic confusion in LTM during recall, suggesting coding is semantic. Also that the sound of the words is not the coding used.

5. Konkle (2010) - LTM, capacity

   • Aims - To investigate the capacity of long term memory.
     • Procedures: Pps were presented with 2912 pictures of scenes from 128 different categories at 3 secs/scene. This was followed by a recognition test after a period of time.
       • Findings: When pps chose between a previously shown scene and a new scene, they were correct 96% of the time.
         • Conclusions: The capacity of the LTM is potentially unlimited and that no matter how much info is stored long-term, it never becomes full.

6. Bahrick et al (1975) - LTM, duration

   • Aims - To investigate very long term memory in a natural setting.
     • Procedures: 392 American ex-high school students aged 17-74 participated in a free recall test, where they had to try and remember names of people in a graduate class. There was also a photo recognition test, consisting of 50 pictures and a name recognition test for ex-school friends.
       • Findings: Pps who were tested within 15-34 years of graduation were ~90% accurate in names and faces. After 48 yrs they were accurate 80% verbal and 40% visual. For free recall, after 15 yrs it was 60% and after 48 yrs it was 30%.
         • Conclusions: Peoples' long term memories can last for their whole life, even though they may weaken over time, and that recognition is better than recall.