Psychology Memory Coding and Capacity

The format in which information is stored in the various memory stores.

Gave different lists of words to four groups of ppts to remember: 1.Acoustically similar (cab, cat, can) 2.Acoustically dissimilar (pit, few, cow) 3.Semantically similar (great, large, big) 4.Semantically dissimilar (good, huge, hot) Ppts were shown the original words and then asked to recall them in the correct order

When they had to do the recall task immediately after hearing it (STM recall), they tended to do worse in acoustically similar words - suggesting that STM is coded acoustically When ppts were asked to recall words after 20 minutes (LTM recall), they did worse on semantically similar words, suggesting LTM is coded semantically.

One limitation of Baddeley's research is that it used quite artificial stimuli rather than meaningful stimuli. The word lists had no personal meaning to participants, which means that we should be cautious about generalising the findings to different kinds of memory task. For example, when processing more meaningful information, people may use semantic coding even for STM tasks. This suggests that the findings from this study may have limited application.

The amount of information that can be held in a memory store

Jacobs

Researcher gives 4 digits, ppt is asked to recall these in the correct order. If they can do this, the researcher reads 5 digits and so on until the ppt is unable to recall the order correctly. This determines the individual's digit span.

mean span for digits was 9.3 items mean span for letters was 7.3

One limitation of Jacobs' study is that it was conducted a long time ago (1887). Early research in psychology often lacked adequate control. For example, some participants may have been distracted while they were tested so they didn't perform as well as they might. This would mean that the results might not be valid because there were confounding variables that were not controlled. Counter-argument: However, the results of this study have been confirmed in other research, supporting its validity.

Miller

Miller noticed people can remember 5 words just as well as they can remember 5 letters. He proposes individuals do this by chunking - grouping the individual letters or numbers into sets/chunks.

Miller

That most adults can store between 7±2 items in their short term memory.

One limitation of Miller's research is that he may have overestimated the capacity of STM. For example, Cowan (2001) reviewed other research and concluded that the capacity of STM was only about four chunks. This suggests that the lower end of Miller's estimate (5 items) is more appropriate than seven items.

believed to be unlimited

The length of time information can be held in memory

Peterson and Peterson

tested 24 undergraduate students on 8 trials. On each trial each student was given a consonant triagram e.g. YCG to remember. They were also given a 3 digit number and told to count backwards from that number to prevent rehearsal. On each trial they were told to stop after a different amount of time (3, 6, 9, 12, 15 or 18 seconds).

They found that the longer the interval, the less accurate the recall. At 3 seconds, around 80% of triagrams were recalled, whereas at 18 seconds only 10% were correctly recalled.

Peterson & Peterson concluded that short-term memory has a limited duration of approximately 18 to 30 seconds.

A limitation of Peterson & Peterson's study is that the stimulus material was artificial. Trying to memorise consonant syllables does not reflect most real-life memory activities where what we are trying to remember is meaningful. Therefore, we might say that this study lacks external validity. Counter-argument: However, we do sometimes try to remember fairly meaningless things such as phone numbers, so the study is not totally irrelevant

Bahrick et al.

studied 392 ppts from the American state of Ohio who were aged between 17 and 74 Recall was tested using photo recognition, some photos from the ppts highschool year book And free recall where ppts recalled all the names of their graduating class

Ppts tested within 15 years of graduation were 90% accurate in recognition, which declined to 70% after 48 years. Free recall was less good - 60% accurate after 15 years and 30% after 48 years Showing the duration of LTM could be unlimited

A strength of Bahrick et al's study is that it has higher external validity than other memory studies. Real-life meaningful memories were studied, which yielded higher recall rates than studies that have used meaningless pictures (e.g. Shepard, 1967). However, a downside of such real life research is that confounding variables are not controlled, e.g. Bahrick's participants may have looked at their yearbook photos and rehearsed their memory over the years.