Cognitive Psychology Studies

Cognitive Psychology Studies

1. STM

   • Duration
     • Peterson and Peterson
       • Procedure
         • Participants were presented with a consonant trigram and asked then asked to count backwards from a three digit number to prevent rehearsal. They were asked to recall after a time delay.
       • Findings
         • After 3 seconds, recall was about 90%
         • After 9 seconds, recall was about 30%
         • After 18 seconds, recall was about 2%
         • This suggests that when rehearsal is prevented, STM lasts around 20 seconds.
       • Conclusion
         • STM has a short duration, unless we repeat something over and over again.
       • Evaluation
         • Lacks ecological validity as material used was artificial
         • The duration could actually be shorter as participants were told the aim and procedure
         • The information could have been replaced with the numbers so the study was actually testing displacement
   • Capacity
     • Miller proposed his theory that STM has a limited capacity of 7+-2 chunks of information.
     • Jacobs conducted a study to measure the capacity of STM
       • Procedure
         • Participants were read lists of either words or numbers and they had to recall immediately after presentation. The length of the digits were increased until recall was accurate 50% of the time.
       • Findings
         • There was a difference between the capacity for numbers compared to letters.
         • The average recall for numbers was 9.3
         • The average recall for letters was 7.3
       • Conclusion
         • It may be easier to recall digits since there are only 10 possible digits whereas there are three letters.
       • Evaluation
         • Cowan reviewed a number of studies and said STM was limited to 4 chunks while a number of other researchers said this is for both verbal and visual information.
         • A number of studies have shown that capacity improves with age, where 8 year olds could remember 606 digits and 18 year olds could remember 806 digits. It could also mean memory techniques increase.
   • Coding
     • Baddely
       • Procedure
         • He presented participants with four lists to remember. List one: acoustically similar, List two: acoustically dissimilar, List three: semantically similar, List four: semantically dissimilar.They were asked to recall as many words as possible immediately after presentation of lists and then try again after 20 minutes.
       • Findings
         • He found that the immediate recall was better for list two than for list one and with little difference in between lists three and four.
         • When participants were asked to recall words after 20 minutes they recalled list four better than list three. There was little difference in recall for lists one and two.
       • Conclusion
         • This shows that short term memory tends to store information according to sounds rather than meaning, and long term memort tends to store information semantically.
       • Evaluation
         • A lab experiment was used therefore has good internal validity.
         • There has been evidence for the use of other coding in STM, it sometimes uses a semantic code, so it is not limtied to acoustic coding.

2. LTM

   • Duration
     • Bahrick et al
       • Procedure
         • 347 participants between 17 and 74 were tested on their long term memory of school friends. A number of different tests were used including free recall, recognition from pictures and name recognition. Yearbooks were used to check accuracy.
       • Findings
         • For participants that left school up to 34 years previously, accuracy of recall was 90%
         • For those who had left school up to 48 years previously, recognition was 80%
       • Conclusion
         • This shows that recall can be accurate for a very long time, leading to the term vLTM to be used to describe this.
       • Evaluation
         • Participants may have seen their classmates after they left school, which explain the long term recall
         • The task may not truly represent long-term memories for the participants may not have had much interest in the pictures
   • Capacity
     • A limit for capacity has never been reached therefore we say it is unlimited.
   • Coding
     • See Baddely

3. Multi-store model

   • Sperling
     • He showed participants a grid of 12 letters for 0.50 milliseconds. They were told to recall on the tone.
     • When asked to recall all 12 items, recall was 42% however when asked to recall one line, recall was 75%
     • This shows that information can quickly decay from sensory memory.
   • Glazner and cunitz
     • The participants were asked to remember a list of 20 words and recall in order.
     • Participants recalled words from the start and end of the list. This is because the words at the start had been rehearsed and transferred into LTM and words at the end were still in short term memory. Words in the middle had been displaced with words at the end of the list.
     • This provides proof that STM and LTM are different stores.

4. Working Memory Model

   • Bunge
     • Used fMRI to see which parts of the brain were active were more active in single and dual tasks.
     • In single and dual tasks the same brain areas were active but more in dual tasks.
     • This indicates that increased attentional demands are reflected in brain activity.
   • Baddely demonstrated the existence of the visual spatial sketchpad.
     • Participants were given a task of tracking a light with a pointer while doing one of two tasks.
     • In task one of describing the angle on a letter F, the task was found more difficult since both tasks used the same slave system.
     • In task two of a verbal task, the task was found much easier since the tasks both used different systems.
     • This study proves the existence of all three slave systems.