P/S 07 · Memory encoding, storage and forgetting
How Memory Works: Four Studies
Interpret studies of serial position, spacing, depth of processing and interference.
Passage
Memory involves encoding information, storing it, and retrieving it later. One influential model describes sensory memory, a short-term or working memory with limited capacity and duration, and a long-term memory with a very large capacity. Information can be moved into long-term memory by rehearsal, and it is remembered better when it is processed in a meaningful way at encoding than when only its surface features are noticed. Forgetting can result from failures of encoding, storage or retrieval, and from interference by other information.
Part 1. In a free-recall study, 60 adults hear a list of 20 unrelated words, one at a time, and are asked to write down as many as they can remember. Half of the participants write them down immediately. The other half first perform a 30-second counting task, which prevents rehearsal, and then write down the words. Table 1 shows the percentage of words recalled from different parts of the list.
Table 1. Percentage of words recalled by position in the list.
| Position in the list | Recalled immediately | Recalled after a 30-second counting task |
|---|---|---|
| First 3 words | 70 | 68 |
| Middle 13 words | 28 | 27 |
| Last 4 words | 78 | 30 |
Part 2. In a second study, 80 students learn the definitions of 40 science terms in 60 minutes of total study time. Half study all of the terms in one hour-long session (massed practice). The other half study the terms in three sessions of 20 minutes, spaced one day apart (spaced practice). Both groups are tested one day after their final session and again one week after their final session, with no further study in between. Table 2 shows the mean percentage of definitions recalled correctly.
Table 2. Percentage of definitions recalled.
| Group | Tested after 1 day | Tested after 1 week |
|---|---|---|
| Massed | 80 | 30 |
| Spaced | 70 | 60 |
Part 3. In a third study, three groups of 30 participants see the same list of 40 words and, for each word, answer one question. The first group answers a question about the shape of the word, such as whether it is written in capital letters. The second group answers a question about its sound, such as whether it rhymes with a given word. The third group answers a question about its meaning, such as whether it would fit in a given sentence. Later, all of the participants are given a surprise recognition test. Table 3 shows the results.
Table 3. Percentage of words recognized.
| Question asked at study | Words recognized (%) |
|---|---|
| Shape of the word | 15 |
| Sound of the word | 30 |
| Meaning of the word | 70 |
Part 4. In a fourth study, participants first learn a list of paired words (List A). One group then rests for 20 minutes, and a second group learns a list of similar paired words (List B). When both groups are tested on List A, the resting group recalls 70% of the pairs and the group that learned List B recalls 40%.
Questions
Question 1 of 6
Why are the first 3 words recalled well under both conditions in Part 1?
Sensory memory lasts only a fraction of a second to a few seconds.
The most recently heard words are at the end of the list. The first words were heard first.
The words are unrelated, and the position, not the meaning, explains the pattern.
Why the answer is what it is
Early items in a list receive more rehearsal and so are more likely to enter long-term memory. This is the primacy effect, and it is not affected by a 30-second delay (70 versus 68).
Review: Learning & Memory
Question 2 of 6
Recall of the last 4 words falls from 78% to 30% after the counting task. What does this suggest?
Information in long-term memory does not usually fade in 30 seconds, and the first words stayed well recalled.
The percentage recalled fell, so memory for those words was weakened.
The words are unrelated, and meaning does not explain why the delay lowers recall of only the last words.
Why the answer is what it is
The last items are still in a short-lived store when recall is immediate. The counting task prevents rehearsal, so these items are lost, while the first words (already in long-term memory) are unaffected.
Review: Learning & Memory
Question 3 of 6
Which result in Table 2 is best described as the spacing effect?
Forgetting over time occurs in both groups, which is not specific to the spacing effect.
This result is true, but it shows the advantage of cramming for a short delay, not the spacing effect.
This is a feature of the design that makes the comparison fair, not a result.
Why the answer is what it is
Spacing study sessions out improves long-term retention. After a week the spaced group recalled 60% and the massed group only 30%, with the same total study time.
Review: Learning & Memory
Question 4 of 6
Based on Table 2, which statement about studying is best supported?
The massed group did better after one day (80% versus 70%).
The massed group recalled only 30% after a week, much less than the spaced group.
The recall differed at both delays, so the methods are not equal.
Why the answer is what it is
The massed group did better after one day (80 versus 70), and the spaced group did much better after a week (60 versus 30). The advantage of each method depends on the delay before the test.
Review: Learning & Memory
Question 5 of 6
What does Table 3 show about the way words are encoded?
The shape question had the lowest recognition (15%).
The recognition rate was 30% for sound and 70% for meaning.
The recognition rates differ widely (15% to 70%), so the question did have an effect.
Why the answer is what it is
Deeper, more meaningful processing leads to stronger memory traces, as in the levels-of-processing framework. Recognition rose from 15% for shape to 30% for sound and 70% for meaning.
Review: Learning & Memory
Question 6 of 6
In Part 4, the group that learned List B recalls fewer pairs from List A (40%) than the resting group (70%). This is an example of:
Proactive interference would show as poor learning of List B because of List A. Here, List A recall was lowered by List B.
Both groups had the same 20-minute delay, and the group that rested remembered more.
The primacy effect refers to better recall of early items within a list.
Why the answer is what it is
Learning the similar List B after List A made it harder to recall A, and the rest of the time was equal. New information interfering with older memories is retroactive interference.
Review: Learning & Memory
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