Lesson 2: Coding, Capacity And Duration Flashcards
Coding: Sensory Register
It is modality specific, each sensory sore codes information differently
Coding: Short-term memory
Baddeley investigated this. He gave participants four lists of words to recall. List A: words sounding similar, List B: words sounding dissimilar, List C: words with similar meanings and List D: words with dissimilar meanings. He argued that STM was coded acoustically because people performed worse recalling words from list A than list B, but there was no difference between list C and D. This means the STM organises information according to how it sounds, similar sounding words can become muddled.
Coding: LTM
Baddeley repeated this experiment to test LTM coding. He tested participants recall of the lists after a 20 minute delay to ensure the info had passed into LTM. Their recall was worse with list C than list D but no difference between list A and B. This means it is coded semantically as LTM organises words by their meanings, so similar meanings can get confused.
Evaluation of coding study by Baddeley
(+) Lab experiment, easy to replicate as variables have been closely controlled, reliability can be assessed.
(-) Findings have low ecological validity. The material (lists) was artificial. Lab setting.
Capacity: Sensory Register
The capacity of the SR is unlimited.
Capacity: STM- Jacobs, Miller
Jacobs used a digit span test to test capacity of STM. He gave participants several sequences of digits or letters asking them to repeat each sequence immediately in the correct order. The sequence got longer by one each time. He found that we can hold an average of 9.3 digits and 7.3 letters. Miller concluded that the span of the STM is 7 (+/-2). If we try to recon more info than capacity, the new info displaces old info. He found that people can recall 5 words as easily as 5 letters so chunking large amounts of information can help us remember more.
Evaluation of Jacobs experiment
(+) Jacob’s research was the first to acknowledge that the STM capacity gradually improves with age
(-) this study was conducted a long time ago so it might not have been done to the same level of rigorous scientific standard as research today, validity can be questioned.
LTM: capacity
Unlimited
Duration: Sensory register
250 milliseconds
Duration: STM
Peterson and Peterson used nonsense trigrams to test STM duration. To prevent maintenance rehearsal they were asked to count backwards from 100 in 3s. After 3 seconds, the recall was accurate 90% of the time, after 9 seconds accuracy= 20% and after 18 seconds= 2%. This concluded that info in STM lasts for 18-30 seconds without rehearsal before it is lost to decay.
Evaluation of Peterson and Peterson (nonsense trigrams)
(+) researchers used fixed timings, eliminated noise and other factors that might influence memory. High level of control and standardised procedure to make sure all participants experienced the same process.
(-) findings may have been caused by interference rather than STM having a short duration. It is possible that earlier learnt trigrams became confused with later ones.
Duration: LTM - Bahrick (classmates)
Bahrick tested 400 people of various ages (17-74) on their memory of their classmates. He used a photo recognition test of participants being shown 50 photos and deciding whether they were their classmates or not. In free recall, they were asked to name people that they could remember from their graduating class. 90% accuracy of photo recognition within 15 years of leaving school and 70% accuracy within 48 years. Free recall= 60% (15 years) and 30% (48 years). This concluded the duration of LTM is potentially a lifetime, but sometimes we have retrieval failure and need retrieval cues to access info.
Evaluation of Bahrick (classmates)
(+) higher ecological validity than Peterson and Peterson’s as material was more meaningful and relevant to everyday life.
(-) problematic to control for extraneous variables e.g. people staying in touch or people looking in their yearbook since leaving.
