coding,capacity and duration EV

What is coding, and who researched it in STM and LTM?

Coding is the process of converting information between different forms, because information is stored in different forms depending on the memory store. Alan Baddeley (1966a, 1966b) researched it.

Describe Baddeley's procedure.

He gave four groups of participants different word lists to remember. Group 1 had acoustically similar words (cat, cab, can), Group 2 acoustically dissimilar (pit, few, cow), Group 3 semantically similar (great, large, big), and Group 4 semantically dissimilar (good, huge, hot). Participants were shown the original words and asked to recall them in the correct order.

What did Baddeley find when participants recalled immediately (from STM)?

Participants tended to do worse with acoustically similar words (Group 1), because words that sound alike get confused in STM.

What did Baddeley find when participants recalled after a 20 minute interval (from LTM)?

Participants did worse with semantically similar words (Group 3), because words with similar meanings get confused in LTM.

What do Baddeley's findings conclude about coding?

Information is coded acoustically (by sound) in STM and semantically (by meaning) in LTM.

What is capacity, and how did Joseph Jacobs (1887) measure the capacity of STM?

Capacity is how much information STM can hold at one time. Jacobs measured it using digit span.

Describe the digit span procedure.

A researcher reads out four digits and the participant recalls them out loud in the correct order. If correct, the researcher reads out five digits, and so on, until the participant cannot recall the order correctly. This indicates the individual's digit span.

What did Jacobs find?

The mean span across all participants was 9.3 items for digits and 7.3 items for letters.

What did George Miller (1956) observe about everyday practice?

He noted that things come in sevens, such as seven notes on the musical scale, seven days of the week and seven deadly sins.

What else did Miller note about recall?

People can recall five words as easily as they can recall five letters. We do this by chunking.

What else did Miller note about recall?

People can recall five words as easily as they can recall five letters. We do this by chunking.

What is chunking?

Grouping sets of digits or letters into units or chunks, which allows us to hold more information in STM.

What is duration, and who studied the duration of STM?

Duration is how long information lasts in a memory store. Margaret and Lloyd Peterson (1959) studied the duration of STM.

Describe the Petersons' procedure.

They tested 24 students in eight trials each (a trial is one test). On each trial the student was given a consonant syllable (such as YCG) to remember, plus a 3-digit number. The student counted backwards from this number until told to stop. This prevented mental rehearsal of the syllable, which would have increased the duration of STM.

What was the retention interval in the Petersons' study?

Students were told to stop counting after varying periods of 3, 6, 9, 12, 15 or 18 seconds.

What did the Petersons find?

After 3 seconds, average recall was about 80%. After 18 seconds, it was about 3%.

What did the Petersons conclude about the duration of STM?

STM duration may be about 18 seconds, unless we repeat the information over and over (verbal rehearsal).

Who studied the duration of LTM, and what was their sample?

Harry Bahrick et al. (1975) studied 392 American participants aged between 17 and 74.

Describe Bahrick et al.'s procedure.

High school yearbooks were obtained from the participants or directly from some schools. Recall was tested in various ways, including (1) a photo-recognition test of 50 photos, some from the participants' high school yearbooks, and (2) a free recall test where participants recalled all the names of their graduating class.

What did Bahrick et al. find for photo recognition?

Participants tested within 15 years of graduation were about 90% accurate. After 48 years, this declined to about 70%.

What did Bahrick et al. find for free recall?

Free recall was less accurate than recognition, at about 60% after 15 years, dropping to 30% after 48 years.

What do Bahrick et al.'s findings conclude about the duration of LTM?

LTM may last up to a lifetime for some material.

What is one strength of Baddeley's study?

It identified a clear difference between two memory stores (STM and LTM).

What did later research show about Baddeley's findings, and why do they still matter?

Later research showed there are some exceptions to his findings. But the idea that STM uses mostly acoustic coding and LTM is mostly semantic has stood the test of time.

Why was Baddeley's study an important step in understanding memory?

It was an important step in our understanding of the memory system, which led to the multi-store model.

What is one limitation of Baddeley's study?

It used quite artificial stimuli rather than meaningful material.

Give an example of the artificial stimuli in Baddeley's study.

The word lists had no personal meaning to participants.

Why might this artificial material be a problem?

Baddeley's findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life. When processing more meaningful information, people may use semantic coding even for STM tasks.

What does this limitation suggest about the study's findings?

The findings from this study have limited application.

What is one strength of Jacobs' study?

It has been replicated.

Why might Jacobs' original study have lacked adequate controls?

It is a very old study, and early research in psychology often lacked adequate controls. For example, some participants' digit spans might have been underestimated because they were distracted during testing (an extraneous variable).

How do we know Jacobs' findings are still reliable despite this?

His findings have been confirmed by other, better controlled studies since (e.g. Bopp and Verhaeghen 2005).

What does this replication suggest about Jacobs' study?

It is a valid test of digit span in STM.

What is one limitation of Miller's research?

He may have overestimated STM capacity.

What did Nelson Cowan (2001) conclude about STM capacity?

After reviewing other research, he concluded that the capacity of STM is only about 4 (plus or minus 1) chunks.

What does Cowan's conclusion suggest about Miller's estimate?

The lower end of Miller's estimate (five items) is more appropriate than seven items.

What is one limitation of Peterson and Peterson's study, and why does it matter?

The results may be due to interference and not decay. They concluded that forgetting in STM was due to the decay of memory traces over time, but it could also be due to interference from counting backwards. This suggests their conclusions about the duration of STM may not be valid.

What is one strength of Bahrick et al.'s study?

It has high external validity, because the researchers investigated meaningful memories (i.e. of people's names and faces).

What evidence supports this strength, and what does it suggest?

When other LTM studies used meaningless pictures, recall rates were lower (e.g. Shepard 1967). This suggests Bahrick et al.'s findings reflect a more "real" estimate of the duration of LTM.