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[dreaming] Initial comments

Hi everybody,
Before I will read your comments on the target paper I will formulate my
first and second impressions (I was referee on two drafts of the paper). If
you did not understand what I say (my native language is German) please do
not hesitate to ask me.

General comments:
I very much appreciate the work of  Raija-Leena Punamäki. Every researcher's
heart will beat faster if she/he had the possibility to analyze such data.
In general, the studied population is very interesting from a political
point of view (a repressed minority).
Although I like the paper there are of course a lot of topics I will address
that I had handled in a different way. It seems that Popper's rational
critizism is crucial for scientific development. If I say everything is okay
nothing will happen.
The comments will be ordered into sections which are parallel to those in
the paper.

I recently published an extensive overview on the dream recall literature
(Schredl, M., & Montasser, A. (1996-97). Dream recall: state or trait
variable? - Part I and Part II. Imagination, Cognition and Personality, 16,
181-210, 239-261.
I found 6 models and hypothesis constructed for explaining intraindividual
and/or interindividual diffenrences in dream recall frequency.

1. Repression hypothesis (Freud)
2. Life-style hypothesis (Schonbar)
3. Interference hypothesis (Cohen and Wolfe)
4. Salience hypothesis (Cohen and MacNeilage)
5. Arousal-Retrieval model (Koulack and Goodenough)
6. Functional state-shift hypothesis (Koukkou and Lehmann)

The research provide some evidence for each of these models but a model
integrating all aspects is lacking. I stress this fact because Punamäki
selected only a few hypothesis of the pool.
In general, there exist serious problems in evaluating the hypothesis since
some of them (repression hypothesis, interference hypothesis, salience
hypothesis) are not testable in a direct way. Contrary to classical memory
theory the original stimuli (experienced dream)  is not measurable. One
could only measure the recalled dream. These remarks should be understood as
hints to be very careful in interpreting the data of the present study but
of all other studies, too.
I personally do not like the mood congruency hypothesis since it is not
testable. How should it be possible to measure dream emotions independendly
from mood after awakening. I would like to name it carry-over effect. It
seems more plausible to me that dreams influence morning mood. Maybe
research, for example carried out by Domhoff (about 1969) support this
hypothesis. He investigated recall of dreams during the day triggered by an

Method section
In a previous draft Punamäki wrote that the participants were intensively
informed about the purpose of the study. Since it was shown that dream
recall frequency could be affected easily by instruction I proposed that
Punamäki should comment on this possibility. Personally, I think the
participants knew very well the aims of the study. Second, the results may
be influenced by experimenter effects since the groups were interviewed by
two different persons. The researcher himself (highly motivated) obtained
the sample with higher dream recall frequency. I think a comment on this
should be given.

Personally, I like the funny sampling method. If you would do such a thing
in Germany, everybody would laugh at you. There is, however, one weakness in
this approach shortly addressed by Punamäki. He did not give a response rate
or a sample size of all potential participants. This could lead to severe
biases in the data.

I have some problems with figures 3 and 4 since they do not depict raw data
but lines computed by the statistic program.
Second, I do not understand the formula for deriving correlations between
dream emotions and morning mood. Is N ranging from 2 to 7. If so, it may be
an artefact that high recallers had higher coefficients since more data
enter in the correlation coefficient.

First, I think it would be very interesting not only measuring dream recall
freqency per se but also analyze frequency of negative dreams or nightmare
frequency (Punamäki elicited it in the composite score sleep difficulties).
In view of the continuity hypothesis I would expect a heightened frequency
of negatively toned dreams.

The above mentioned objections to the testability of the salience hypothesis
should lead to very careful conclusion. In a recently conducted study we
found that high recallers reported more positive emotions than low recallers
whereas negative emotions do not differ. We explained this fact that high
recallers are more trained in recalling dream content since research has
shown that positive emotions were often not mentioned explicitely (Hall and
Van de Castle). I cite this data since I would like to stress the fact that
one could not be sure of the direction or of causal relationships. Sleep
laboratory data exploring the relationship between physiological and/or
cortical arousal and dream recall after awaking lead to contradictory results.
I would like to add a possible causal mechanism. Since we have shown that
sleep quality and frequency of noctural awakenings correlate substantially
with dream recall frequency it may be plausible that stress affected sleep
quality and nocturnal awakening and, therefore, dream recall is heightened.
This would be fit in the arousal-retrieval model of dream recall.

The regression analysis (exept for analysis regarding dream salience)
yielded coefficients of explained variance of about 10 %. This should be
interpreted in the following way: The elicited measures are only few of a
larger pool which may influence dream recall frequency. So the confirmed
hypotheses could only explain a small portion of the whole variance and one
should give attetion to further factors affecting dream recall.

Dipl. Psych. Michael Schredl
Sleep laboratory
Central Institute of Mental Health
P. O. Box 12 21 20
68072 Mannheim
Telefon: Germany 0621/1703-602
Fax: Germany 0621/23429
Homepage: http:/www.zi-mannheim.de/schlaflab/abteilung.htm