From the article : Creating False memories : Remembering words not presented in

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From the article : Creating False memories : Remembering words not presented in lists by Henry L. Roediger II

Results

Recall. The mean probability of recall of the studied words

was .65, and the serial position curve is shown in Figure 1. The

curve was smoothed by averaging data from three adjacent

points for each position because the raw data were noisy with

only six lists. For example, data from the third, fourth, and fifth

points contributed to the fourth position in the graph. The first

and the last positions, however, were based only on the raw

data. The serial position curve shows marked recency, indicating

that subjects followed directions in recalling the last items

Serial Position

Figure 1. Probability of correct recall in Experiment 1 as a function of

serial position. Probability of recall of the studied words was .65, and

probability of recall of the critical nonpresented item was .40.

first. A strong primacy effect is also apparent, probably

because the strongest associates to the critical target words

occurred early in the list. The critical omitted word was

recalled with a probability of .40, or with about the same

probability as items that had been presented in the middle of

the list (see Figure 1). Therefore, items that were not presented

were recalled at about the same rate as those that were

presented, albeit those in the least favorable serial positions.

The average output position for recall of the critical nonpresented

word was 6.9 (out of 8.6 words written down in lists in

which there was a critical intrusion). The cumulative production

levels of the critical intrusion for those trials on which they

occurred is shown in Figure 2 across quintiles of subjects'

responses. The critical intrusion appeared only 2% of the time

in the first fifth of subjects' output but 63% of the time in the

last quintile. Thus, on average, subjects recalled the critical

nonstudied item in the last fifth of their output, at the 80th

percentile of recalled words (6.9 •*- 8.6 x 100).

Output Quintile

Figure 2. Recall of the critical intrusion as a function of output

position in recall. Quintiles refer to the first 20% of responses, the

second 20%, and so on.

806 HENRY L. ROEDIGER III AND KATHLEEN B. McDERMOTT

Other intrusions also occurred in recall, albeit at a rather

low rate. Subjects intruded the critical lure on 40% of the lists,

but any other word in the English language was intruded on

only 14% of the lists. Therefore, subjects were not guessing

wildly in the experiment; as usual in single-trial free recall, the

general intrusion rate was quite low. Nonetheless, subjects

falsely recalled the critical items at a high rate.

Recognition. The recognition test was given following study

and recall of all six lists, and thus the results were likely

affected by prior recall. (We consider this issue in Experiment

2.) The proportion of responses for each of the four confidence

ratings are presented in Table 1 for studied (old) items and for

the three different types of lures: unrelated words, weakly

related words, and the critical words from which the lists were

derived. Consider first the proportion of items subjects called

old by assigning a rating of 3 (probably old) or 4 (sure old). The

hit rate was 86% and the false-alarm rate for the standard type

Of unrelated lures was only 2%, so by usual criteria subjects

showed high accuracy. The rate of false alarms was higher for

the weakly related lures (.21) than for the unrelated lures,

t(35) = 7.40, SEM = .026, p < .001. This outcome replicates

the standard false-recognition effect first reported by Underwood

(1965). The false-recognition rate for weakly related

lures was greater than obtained in many prior studies (e.g.,

L. M. Paul, 1979), and the rate for the critical nonpresented

words was dramatically larger than the rate for the weakly

related words. As shown in Table 1, the false-alarm rate for the

critical nonstudied lures (.84) approached the hit rate (.86),

r(35) < 1,SEM =.036,™.

Consider next the results based on subjects high-confidence

responses (i.e., when they were sure the item had appeared in

the study list and rated it a "4"). The proportion of unrelated

and weakly related lures falling into this category approached

zero. However, subjects were still sure that the critical nonstudied

items had been studied over half the time (.58). The hit

rate for the studied items remained quite high (.75) and was

reliably greater than the false-alarm rate for the critical lures,

f (35) = 3.85, SEM = .044,/> < .001. It is also interesting to look

at the rates at which subjects classified items as sure new.

Unrelated lures were correctly rejected with high confidence

80% of the time. Related lures received this classification only

44% of the time, and critical lures were confidently rejected at

an even lower rate, 8%, which is similar to the rate for studied

words (5%).

Table 1

Recognition Results for Experiment 1: The Proportion of Items

Classified As Sure Old (a Rating of 4), Probably Old (3),

Probably New (2), or Sure New (1) and the Mean Ratings of

Items As a Function of Study Status

Study status

Studied

Nonstudied

Unrelated lure

Weakly related lure

Critical lure

Old

4

.75

.00

.04

.58

3

.11

.02

.17

.26

New

2

.09

.18

.35

.08

1

.05

.80

.44

.08

Mean

rating

3.6

1.2

1.8

3.3

Table 1 also presents the mean ratings for the four types of

items on the 4-point scale. This measure seems to tell the same

story as the other two: The mean rating of the critical lures

(3.3) approached that of studied items (3.6); the difference did

reach significance, t(35) = 2.52, SEM = .09, p < .05. In

general, the judgments subjects provided for the critical lures

appeared much more similar to those of studied items than to

the other types of lures.

Question is:

1) State the findings from Experiment 1 which allowed the authors to conclude that the critical non-presented were recalled at about the same level as items actually presented, and that this high rate of falase recall was not due to participants guessing wildly.

Briefly summarise the overall results from the 2 experiments

Explanation / Answer

1) State the findings from Experiment 1 which allowed the authors to conclude that the critical non-presented were recalled at about the same level as items actually presented, and that this high rate of false recall was not due to participants guessing wildly.

In the first figure, the probability that the presented words were recalled was 0.65 and also that, even when the words were not given , they were recalled, I.e. Non presented words was given as 0.4. Also, the recalled words present in the middle of the list and the omitted words, occurred with the same probability, I.e. 0.4. Hence, the scientists concluded that the presented data was recalled at the same rate as the non presented data.

2. Briefly summarise the overall results from the 2 experiments

In the second experiment also, it was observed that, recall of the non studied items was found in the 80th percentile of the words that were recalled. Ultimately, both the graphs and data gave similar results, that recall of non presented words are at a very similar rate to the presented data. This implies, that high rate of false recall occurs in patients and can be facilitated by particular therapeutic procedures. Also, recognition in which unrelated subjects were confidently rejected and related lures, were not rejected by that confidence, but was confused at a very high rate.

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