Laws, K.
R., & Bhatt, R. (2005). False memories and delusional ideation in normal healthy subjects.
Personality and Individual Differences,
39, 775 – 781.
Past research has shown
deficits in memory of individuals with schizophrenia, specifically increased
errors of omission (forgetting).
However, very little research has been conducted examining errors of
commission (false memories) in this population.
Past research has suggested a connection between memory deficits and
delusional thinking, a common characteristic of schizophrenics.
Methods
Participants.
One hundred and five student from a college population
were included in the study. These
participants were divided into two groups based on a median split of PDI
scores. This split resulted in a low PDI
group of 54 participants and a high PDI group with 51 participants.
Materials.
The current study made use of the Peters et al. Delusional Inventory (PDI,
1999), which measures delusional thinking using a 40 question measure. (E.g., Do you ever feel as if you are a robot or zombie without a
will of your own?). Additionally, the
study included use of the DRM paradigm.
Each participant studied 8 lists (15 Items) from R&M (1995), and
completed a recall test (2.5 Min) for each list immediately after its presentation. Upon completion of this process for all eight
lists, a 23-item recognition test was administered. This list included 8 target
words from the list, 8 critical lures, and 7 unrelated words. The purpose of this recognition task was to
determine the confidence levels for the responses of the participants. Confidence was rated on a four points scale:
1-sure it was new, 2-probably it was new, 3-probably
it was old and 4-sure it was old.
Results
Recall (Table 1)
These data suggest that the high PDI group (more
delusional characteristics) recalled significantly more critical lures (called
targets in the table) and other words than the low PDI group. Also, the high PDI group recalled fewer
correct items.
Recognition (Table 2)
Analogous findings are evident in the recognition
data. The high PDI group showed
significantly higher levels of high confidence acceptance of critical lures and
unrelated items, while showing significantly lower levels of high confidence
rejection rates of critical lures and unrelated items than did the low PDI
group. There were no significant
differences found between the groups when considering recognition of previously
studied items.
Significant differences were also found between the
groups when considering the Knowledge Corruption Index (KCI) which considers
the proportion of errors that are rated with high confidences in relation to
the total number of errors. The high PDI
group showed a significantly higher KCI score than the low PDI group (46% vs.
27%) overall. A more specific evaluation
of KCI for false positive errors showed the analogous significant difference
(41% vs. 24%)
Conclusions
Overall, the high PDI group showed deficits in memory,
both in recognition and recall.
Importantly, this group also showed significant overconfidence in their
memory. Past research of schizophrenics
using the DRM did not result in similar findings to those in this study. A few potential reasons were sighted for this
inconsistency. First, the sample in the previous study did not delineate
between schizophrenics with high and low levels of delusional ideation. As such, this
characteristics may not be indicative of the general idea of
schizophrenia. Second, the relation between memory and delusions might only
exist in individuals without schizophrenia.
Finally, schizophrenics in the previous research showed poor memory
overall, thus creating a difficult situation within which to detect
differences.
Important Legal
Disclaimer: The preceding are articles we read together in the Lampinen Lab Spring 2006 false memory reading group. By
clicking on the button next to the article you can see the summary of that
article. The summary was prepared by the student presenting that article and it
is of course the case that the views expressed in the summary do not
necessarily represent the views of the reading group as a whole, Dr. Lampinen, the Lampinen Lab,
Hugo's, the University of Arkansas, the Razorback Football or Basketball teams
(although we're not sure about cross country), people living down the street
from us, Bob Dylan, Jack Fate, our extended families, or anyone else for that
matter except for the student who wrote the summary (and they don't necessarily
believe what they wrote either).