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International Journal of Dream Research Volume 7, No. 1 (2014) 61
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Lucid dream induction by visual and tactile stimulation
1. Introduction
In a lucid dream the dreamer is not only aware of the fact
that he or she is dreaming, but is also able to control the
dream content (LaBerge, 1985). Lucid dreams can occur
spontaneously or can be induced by different techniques
(cf. Stumbrys, Erlacher, Johnson & Schredl, 2014). Stum-
brys, Erlacher, Schädlich and Schredl (2012) differentiated
lucid dream induction techniques into two main categories:
Cognitive techniques and external stimulation. Cognitive
techniques include all cognitive activities that are carried out
to increase the likelihood of achieving lucidity in the dream
state (e.g. lucid awareness training). The rationale behind
the second category is that an external stimulus presented
to a sleeping person can be incorporated into their dream.
For example, Dement and Wolpert (1958) sprayed water on
uncovered body parts of twelve participants while they were
in REM sleep. In 33 trials, where participants did not awake
from the procedure, dream reports revealed in 42 % of the
cases that water-spray was incorporated into the dream
(e.g. sudden rainfalls, leaking roofs, or being squirted by
someone). For lucid dream induction the idea is that the in-
corporated stimulus serves as a cue for the dreamer which
reminds him of the dream state, e.g., someone squirts water
reminds the dreamer that he or she is dreaming.
Sleep laboratory research demonstrated that external
stimuli applied to most of the sensory modalities (e.g. audi-
tory stimulation) are able to be incorporated in at least some
dreams (cf. Nielsen, 1993). However, incorporation rates
vary massively, e.g., Dement and Wolpert (1958) presented
a tone or light ashes but they were incorporated in only 9 %
and 23 % respectively – which is far less than using water-
spray (42 %) (for an overview see: Nielsen, 1993). Therefore
it seems that some stimuli might be superior when it comes
to lucid dream induction than others. In the review by Stum-
brys et al. (2012) eleven studies were identied which used
external stimulation during REM sleep to trigger lucidity.
External stimulation includes light stimuli, acoustic stimuli,
vibro-tactile stimuli, electro-tactile stimuli, vestibular bodily
stimuli and water stimuli (overview: Stumbrys et al., 2012).
Hearne (1978) rstly reported a study with external stimu-
lation for lucid dream induction. He was inspired by the nd-
ings of Dement and Wolpert (1958) and used water-spray to
induce lucidity in an experiment with 10 participants who
spent a single night in the sleep laboratory. Results revealed
that water-spray was incorporated in 60 % of the dream
reports, but no lucid dream was provoked. In a later study,
Hearne (1983) applied electrical impulses at the wrist. This
time, six out of 12 participants (50 %) who spent a single
Lucid dream induction by visual and tactile stim-
ulation: An exploratory sleep laboratory study
Franc Paul1, Melanie Schädlich2, & Daniel Erlacher3
1Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University,
Germany
2Institute of Sports and Sports Sciences, Heidelberg University, Germany
3Institute of Sport Science, University of Bern, Switzerland
Corresponding address:
Franc Paull, Sleep laboratory, Central Institute of Mental
Health, PO Box 122120, 68072 Mannheim, Germany.
Email: franc.paul@zi-mannheim.de
Submitted for publication: March 2014
Accepted for publication: April 2014
Summary. In a lucid dream the dreamer is aware of the dream state. Previous research has shown that external stimuli
(e.g. ashing lights) presented to a person during REM sleep can trigger lucidity. To further examine the possibility of lucid
dream induction by external stimulation, visual and tactile stimuli were investigated in an exploratory sleep laboratory
study. In the rst experiment 10 participants spent two none-consecutive nights in a sleep laboratory. In the rst night
a visual stimulus (ashing lights) was presented during REM sleep and in the second night tactile stimulation (vibration)
at the index nger was utilized, again in REM sleep. In the second experiment 14 participants spent a single night in the
sleep laboratory and tactile stimulation (vibration) either at the wrist or at the ankle was applied during REM sleep. The
participants were instructed to perform two consecutive left-to-right eye movements to indicate lucidity in the dream.
Light stimulation yielded one signal-veried lucid dream out of 18 application trials (5.6 %) whereas tactile stimulation at
the index nger did not provoke any lucid dream at all (21 applications). Tactile stimulation at the wrist or ankle resulted
in two signal-veried lucid dreams out of 27 trials (7.4 %). Stimuli were incorporated in 38.9 %, 42.9 %, and 55.6 % of
stimulations, respectively. The results suggest that lucid dreams can be triggered by visual or tactile stimulation. Howev-
er, the frequencies of the induced lucid dreams are – in comparison to earlier studies – quite low. Furthermore, for tactile
stimulation it seems important at which part of the body the stimulation is applied. In general, the intensity of stimulation
needs to be adjusted because stimulation often led to an awakening of participants. Thus it seems important for future
studies to focus on factors like waking thresholds and preparation of participants in order to minimize awakenings and
to maximize lucid dream induction.
Keywords: Lucid dream induction, visual stimulation, tactile stimulation, incorporation
Lucid dream induction by visual and tactile stimulation
International Journal of Dream Research Volume 7, No. 1 (2014)62
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night in the sleep laboratory achieved lucidity. Two other
participants also became lucid, but woke up at signalling
and another one became lucid after falsely perceiving stim-
ulation. In one eld study tactile stimulation was also utilized
for lucid dream induction (Reis, 1989). However, these nd-
ings are limited because vibro-tactile stimulation was used
in an unsystematic way either alone or in combination with
reection technique and/or acoustic stimulation. Whereas
the tactile cues alone induced no lucid dream, the combi-
nation seemed to have an effect in 50 % of the cases. But
again, due to a great variety of conditions used (e.g. training
sessions) interpretations should be carried out carefully.
Beside tactile stimuli, visual stimulation with ashing lights
appears to be a promising way of cuing lucidity during REM
sleep. LaBerge and colleagues conducted four studies: One
sleep laboratory experiment (LaBerge, Levitan, Rich & De-
ment, 1988) and three eld studies which used self-con-
structed and commercially available devices (e.g. Dream-
Light) to present light stimuli during REM sleep (LaBerge &
Levitan, 1995; LaBerge, 1988a; Levitan & LaBerge, 1994).
In the sleep laboratory study (LaBerge et al., 1988), 24 of
44 participants (55 %) reported one or more lucid dreams.
However, participants spent one to ve nights (for a total of
58 recording nights) in the laboratory and therefore, chances
to experience a lucid dream are higher in comparison to the
single-night study by Hearne (1978). In the eld studies, the
success rates are even higher: 70 % of the participants in
the study by Levitan and LaBerge (1994) and almost 80 % of
the participants in the study by LaBerge and Levitan (1995)
experienced at least one lucid dream (no exact gures avail-
able for LaBerge, 1988a). These gures only provide infor-
mation about the amount of participants who achieved lu-
cidity, the number on trials/nights is disregarded with this
approach. For example, if two participants sleep ve nights
with an induction device and each person reports one lu-
cid dream, the induction rate would be 100 % when only
the number of partcicpants who got lucid is taken into ac-
count. As a consequence, induction rates appear to be very
high. But if one only counts the number of nights with lucid
dreams, the induction rate is just 20 % (two lucid dreams
in ten nights). All of the eld studies allow such statements
about the frequency of successfully induced lucid dreams
in relation to the number of awakenings or stimulation trials.
Levitan and LaBerge (1994) reached 3.7 %, LaBerge and
Levitan (1995) 27.16 % (with 12.35 % lucid dreams in a con-
trol grout without stimulation) and LaBerge (1988a) 5.5 % of
lucid dreams. But again, the total number of nights for each
participant slept with the DreamLight ranged in the study
by LaBerge and Levitan (1995) for example from four to 24
nights. Furthermore, the eld studies lacked of the objective
validation of lucidity by eye-signaling, which usually leads to
higher lucid dream rates compared to the more conserva-
tive sleep laboratory criterias with eye-signaling (e.g. Kueny,
1985, where 22 lucid dreams were reported but only ve
could be conrmed by eye signals and sleep stage).
Up to now only a few laboratory studies investigated ex-
ternal triggers for lucid dream induction and the results for
tactile stimulation seems unclear. Visual cues revealed good
results, however, multiple trials with a single participant
have been allowed and only one study was conducted in
a sleep laboratory. Furthermore, all studies were adminis-
tered by LaBerge and his colleges with their own products
(DreamLight, NovaDeamer etc.) and an independent repli-
cation of the results would be desirable. The purpose of this
exploratory study was to further explore the effectiveness of
tactile and visual stimulation to induce lucid dreams utiliz-
ing a standardized procedure in a sleep laboratory setting.
The aims were to test the feasibility to apply external stimuli
during REM sleep and to replicate the ndings of previous
studies to trigger lucidity by external stimulation. We con-
ducted two experiments with three different conditions: Vi-
sual stimulation with ashing lights, tactile stimulation at the
index nger, and tactile stimulation at the wrist or ankle.
2. Method
2.1. Participants
The participants were students from Heidelberg University
and took part in a weekly seminar about lucid dreaming and
sports at the Institute of Sports and Sports Sciences given
by one of the authors (D.E.) in summer semester 2008 and
winter semester 2008/2009. Participants were self-selected
by their interest in dreams and lucid dream research. No
exclusion criteria were made. There was neither a frequent
lucid dreamer among the sample nor did participants use
any induction technique in the past on a regular basis (see
also Table 1). Ten students (5 male, 5 female) with a lucid
dream frequency of 0.8 per month participated in the rst
experiment and in the second study 14 students (7 male, 7
female) with a mean lucid dream frequency of 0.5 per month
were included. Participation in the laboratory study was part
of the seminar requirement.
2.2. Experimental conditions
The stimuli or stimulation devices of the three conditions
were as follows:
Visual stimulation. The light stimuli were two ashing red
LEDs mounted in a pair of self-made goggles. The ashing
frequency was 1 Hz and one application lasted ve sec-
onds.
Tactile stimulation – index nger. A self-build vibration
device made from a small vibrating motor typically build in
mobile phones was applied to the index nger of the non-
dominant hand. The sensation was comparable to the vi-
brating alert of a mobile phone. Simulation lasted for a max-
imum of two seconds.
Tactile stimulation – wrist or ankle. The vibration device
described above was applied either to the wrist or ankle.
Stimulation of wrist or ankle was done separately in ran-
domized order for a maximum of two seconds.
Despite acoustic stimulation was also often used in past
studies we followed the suggestion by Price, LaBerge,
Bouchet, Ripert and Dane (1986) not to use auditory cues
because they are more likely to produce arousals since the
auditory system is more associated with monitoring the en-
vironment.
The stimulation was always carried out during REM sleep
by an experimenter who monitored the overnight sleep re-
cording. The experimenter was able to adjust the intensity
and duration of the tactile stimulus within a small range.
The rst stimulation trial always started with one second at
the lowest intensity. If participants did not wake up due to
stimulation and if there was no incorporation in the dream
report after REM awakening, the intensity was increased in
the next REM period. If there was still no awakening or in-
corporation, the length of stimulation increased to two sec-
International Journal of Dream Research Volume 7, No. 1 (2014) 63
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Lucid dream induction by visual and tactile stimulation
onds. Within each trail the intensity and duration stayed the
same. The visual stimulation could not be altered in intensity
or length.
2.3. Sleep recordings
An overnight polysomnography (PSG) according to Re-
chtschaffen and Kales (1968) was conducted to register
sleep stages. PSG included two electroencephalogram
(EEG) channels (C3-M2, C4-M1), two electrooculogram
channels (EOG) (E1-M2, E2-M2), an electromyogram (EMG)
with submental electrodes as well as an electrocardio-
gram (ECG). Sleep stages were scored according to Re-
chtschaffen and Kales (1968).
2.4. Procedure
The participants slept two none-consecutive nights (ex-
periment 1) or a single night (experiment 2) in a dark
and quiet room at the Institute of Sports and Sports
Sciences(Heidelberg University) with continuous PSG re-
cording (from about 11:00 pm to about 8:00 am). Partici-
pants arrived at 9:00 pm and the experimenter familiarized
them with the room and setting. Afterwards participants
prepared themselves for the night and all electrodes were
attached by the experimenter. Before going to sleep, all par-
ticipants were instructed about the stimulus and the possi-
bility of incorporation in their dreams. They got the following
explanation in verbal and written form.
“The stimulus will be demonstrated before sleep. You
should pay attention to the stimulus and its sensation and
indicate us, whether you recognized it or not. Think about
the stimulus before sleep and imagine its sensation. If you
recognize the stimulus in your dream, you should get aware
of dreaming. The stimulus can appear in different forms in
your dream, be aware that any kind of the respective sensa-
tion could be a sign of dreaming. Signal lucidity by two con-
secutive left-to-right eye movements (LRLR). After a while,
you will be awakened and have a chance to write down your
dream report.”
2.4.1 Stimulation and REM awakenings
The stimulation was carried out in each REM period, start-
ing with the third REM period of the night because the rst
two REM periods are usually not long enough to guaran-
tee stable REM sleep for stimulation (cf. Dement & Wolpert,
1958). Stimulation was started after ve minutes of REM
sleep in the third REM period and after ten minutes of REM
sleep in all following REM periods. In each REM period ve
stimulations for the length of ve seconds (light stimulation)
or a maximum of two seconds (tactile stimulation) were con-
ducted in one minute intervals (see Figure 1). After the fth
application the experimenter waited another minute before
awakening participants through an intercom system. Stimu-
lation was stopped if participants signaled lucidity by LRLR,
REM sleep was discontinued, or participants woke up.
After every awakening the experimenter asked all partici-
pants whether they could recall a dream or not (‘What was
on your mind before you woke up?’) through the intercom
system. When the answer was afrmative, the experimenter
went into the room and participants were asked to write
down their dream and to evaluate the following questions:
(1) Was the stimulus incorporated into the dream (yes or
no)? (2)Where you awakened by the stimulation (yes or no)?
On which part of the body did you perceive the stimulation
in the dream (wrist or ankle; only condition 3)? (3) Did you
become lucid (yes or no)? After the report had been com-
pleted participants continued sleeping.
For each REM period, the experimenter noted the onset
of REM, the time of the stimulation, comments about the
awakening and stimulus application and whether the EOG
showed the respective eye movements indicating lucidity.
2.4.2 Statistical Analysis
Because this is an exploratory study, the main focus is on
descriptive statistics. Effect size h was calculated for each
condition according to Cohen (1992). For these calculations,
the percentages of participants with successfully induced
lucid dreams in each condition were compared to a sample
of a study by Stumbrys, Erlacher and Schredl (2013b). In
this study, a sham lucid dream condition with 19 partici-
pants and a mean of 3.2 awakenings in a single night led to
no lucid dream. Cohen (1992) differentiated between small
(h = 0.1-0.4), medium (h = 0.41-0.70) and large (h> 0.71)
effect sizes. IBM SPSS Statistics 20 software was used for
the descriptive statistical analysis.
3. Results
Table 2 depicts the number of stimulated REM periods,
dream reports, incorporations and lucid dreams for all con-
ditions.
3.1. Lucid dreams
For visual stimulation, one out of ten participants reported
a lucid dream (10 % of participants; 5.6 % of all dream re-
ports). This lucid dream was veried by LRLR eye signals.
In the dream report the participant stated that light was in-
corporated in his dream and triggered lucidity (“Again, I was
Table 1. Participant characteristics
Variable Sample Age
(years)
Dream recall fre-
quency1
(dreams/week)
Lucid dream recall
frequency2 (lucid
dreams/month)
Visual stimulation
Tactile stimulation – index nger.
10 (5 male, 5 female) 24.4 ± 1.2 3.0 ± 1.7 0.8 ± 1.4
Tactile stimulation – wrist or ankle 14 (7 male, 7 female) 24.2 ± 2.2 3.2 ± 2.2 0.5 ± 1.1
1Dream recall frequency was assessed on a 7-point scale ranging from 0 - never to 6 - almost every morning (Schredl, 2004).
2Lucid dream frequency were assessed on a 8-point scale ranging from 0 - never, to 7 - several times a week (Stumbrys, Erlacher, Schredl, 2013a)
Lucid dream induction by visual and tactile stimulation
International Journal of Dream Research Volume 7, No. 1 (2014)64
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at that party and saw those lights. This time I responded
immediately with eye signals”). Two more participants re-
ported a lucid dream but had to be dismissed because in
the rst case the participant was uncertain if she really had
a lucid dream (no eye signal could be detected in EOG re-
cording) and in the second case the participant was uncer-
tain if she had been dreaming at all (PSG recording revealed
that she had actually been awake). The effect size, in terms
of the number of participants with successfully induced lu-
cid dreams, was h = 0.64 compared to the above mentioned
sham condition by Stumbrys et al. (2013b).
For tactile stimulation at the index nger, no lucid dream
was reported by the 10 participants.
In the second tactile experiment, the stimulus was applied
36 times (20 stimulations at the ankle and 16 at the wrist).
Two out of 14 participants reported a lucid dream triggered
by stimulation at the ankle (14.3 % of participants; 7.4 % of
all dream reports). Both lucid dreams were veried by LRLR
eye signals. In the rst lucid dream the participant reported
explicitly that the vibration at the ankle triggered lucidity (“I
run up the hill, when a vibration at the ankle let me realize
that I was only dreaming”). The same participant reported a
second lucid dream, but PSG recordings indicated that he
was awake. In the second case the vibration was not ex-
plicitly stated in the dream report (“In the restaurant was no
seat for me and I had to get a coffee-to-go. In the hallway,
I started the lucidity task and counted the steps.”), but in
the protocol she conrmed that a vibration occurred in the
dream. In this condition, the effect size in terms of the num-
ber of participants where lucid dreams were successfully
induced, was h = 0.78 compared to the sham condition by
Stumbrys et al. (2013b).
3.2. Incorporation rates and awakenings
In the case of visual stimulation, 18 dreams out of 24 awak-
enings were reported. Incorporation was self-reported in
seven dreams (38.9 %). In eight stimulations (33.3 %) the
participant was awakened by the procedure (ve times after
the rst stimulation and three times after the fourth stimula-
tion; see Table 3) and six times no dream was recalled.
For tactile stimulation at the index nger, 21 dreams were
reported (out of 24 awakenings). Incorporation was self-re-
ported in nine dreams (42.9 %). In 13 stimulations (54.2 %)
participants were awakened by the procedure (ve times af-
ter the rst stimulation, two times each after the second and
third stimulation, and four times after the fourth stimulation;
see Table 3) and three times no dream was recalled.
For tactile stimulation at the ankle or wrist, 36 awakenings
yielded in 27 dreams reports. Incorporation was self-report-
ed in 13 dreams (48.1 %). In 15 stimulations (41.7 %) partici-
pants were awakened by the procedure and nine times no
dream was recalled. Regarding the question at which part
of the body the stimulation had been perceived, the correct
answer was given in 16 stimulations and in two trials the
wrong part was reported. In the remaining three trials par-
ticipants perceived the vibration in different forms (e.g. the
whole body was vibrating).
4. Discussion
In this study, external visual and tactile stimulation was in-
vestigated with the objective to induce lucidity during REM
sleep. Induction rates related to the number of awakenings
were comparable to earlier studies; however, the total num-
ber of participants who achieved lucidity was rather low.
Figure 1. Example for one stimulation trial
Table 2. Main results of the three different stimulation techniques
Variable N Stimulated REM
periods
Dream reports Incorporation Lucid dream
Visual stimulation110 24 18 7 (38.9 %) 1 (5.6 %)
Tactile stimulation (index nger)110 24 21 9 (42.9 %) 0 (0 %)
Tactile stimulation (wrist or
ankle)
14 36 (20x wrist,
16x ankle)
27 13 (48.1 %) 2 (7.4 %)
Note. 1Participants were the same.
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Lucid dream induction by visual and tactile stimulation
Taken the three studies together, lucid dream rates were
about 4.3 % and incorporation rates about 43.3 %. In al-
most half of the trials participants were awakened by the
stimulation in the tactile stimulation conditions (54.2 % and
41.7 %)and in one third of the cases during visual stimula-
tion (39%).
4.1. Limitations
Before discussing the results, some limitations of the pres-
ent study should be acknowledged. There was no control
group or condition in our experiment. Data from another
lucid dream induction study by a member of our research
group was used to compare our results with (Stumbrys et
al., 2013b). In this study, transcranial direct current stimu-
lation (tDCS) was applied in REM sleep to induce lucidity.
Eleven of the 19 participants could be described as frequent
lucid dreamers (at least once a month according to Sny-
der and Gackenbach, 1988). In the sham night (without any
stimulation), no lucid dream was reported. The problem with
this comparison is that participant’s characteristics (in terms
of lucid dream frequency, interest in lucid dreams, regular-
ity and method of practice etc.) of each investigation differ
more or less. In a study by LaBerge and Levitan (1995) for
example, the lucid dream rate in a control condition without
any stimulation was 12.35 %. Their participants were de-
scribed as highly interested in lucid dreams with previous
experience in lucid dreaming. We suggest that future stud-
ies should always include control conditions and evaluate
the previous experience of their participants very precisely.
Otherwise, general conclusions could not be drawn.
There are some general methodological problems which
have to be addressed. One issue refers to the measurement
of dream lucidity. For example, in Kueny’s (1985) study 22
participants reported a lucid dream, but after examining the
PSG recordings, she was able to conrm only ve of them in
terms of correct stage (REM) and the presence of eye move-
ments (to indicate lucidity). When only dreams are classied
as lucid in which clearly detectable eye signals are present
(in stage REM), the denition of lucid dreams is disregarded.
Lucid dreams are not dened as a dream where volitional
eye signals are present. Most of the past studies, especially
those using visual stimulation and generally all eld experi-
ments did not use volitional eye signals to evaluate dream
reports. On the other hand, it is important to have an ob-
jective measure of lucidity in comparison to the subjective
dream reports by examining the PSG recordings at the time
of the eye signals,. We utilized the more stringent condition
to determine lucidity by evaluating sleep stages and eye
signals like Kueny (1985). Thus, we were able to conrm
three of the six reported lucid dreams.
The same problem applies to the rating of awakenings.
We asked participants (subjective perception) and experi-
menters (judging PSG recordings) whether the stimulations
caused an awakening or not. Both, experimenters and par-
ticipants were sometimes insecure or their judgments were
contradictory. In some cases it was difcult to clearly dif-
ferentiate between light sleep, REM sleep and waking state.
This problem will be even more severe when experimenters
with little experience in sleep stage scoring have to judge
about the awakenings. The classication of lucidity and
sleep stages can be optimized by asking several experi-
enced blind judges to rate dream reports, eye signals and
sleep stages independently.
Another methodological issue deals with the question
whether the stimulation triggered lucidity or a lucid dream
occurred by chance or even triggered by other cues (e.g.
the sleep laboratory environment or bizarre dream features).
Therefore, we recommend using control conditions.
Further limitations of our study are the small sample size
and the (self) selection of participants.
4.2. Comparison to earlier studies
Concerning visual stimulation, our induction rate of 5.6%
reects LaBerge’s (1988) nding of 5.5 % of lucid dreams
when only the DreamLight was used. Both studies did not
utilize other induction techniques like for example verbal
suggestion. Consequentially, it could be argued that visual
stimulation seems to be inferior compared to other external
cues. In the present study tactile stimulation yielded in a 7.4
% lucid dream rate. In the single tactile stimulation study
(Hearne, 1978) with untrained participants (spraying water)
no lucid dreams were reported. Later, Hearne (1983) used
electrical impulses to induce lucidity and 8 out of 12 partici-
pants reported lucid dreams. However, her 8.3 % of lucid
dreams without stimulation suggest that the participants
were more or less frequent lucid dreamers. Other investiga-
tions with tactile stimulation could not be compared with
our study because other/multiple training methods have
been used.
Although a combination of different training methods (e.g.
intention technique, autosuggestion, wake back to bed)
cannot reveal effects of external stimulation as a single
technique, this approach should be considered, especially
with participants who are unfamiliar with lucid dreaming.
Concerning visual stimulation, ndings of LaBerge (1988)
and Levitan and LaBerge (1994) indeed suggest that light
stimuli in combination with cognitive techniques (e.g. MILD)
seem to be more effective.
Motivational factors are often discussed to be important
for achieving lucidity too (e.g. Price & Cohen, 1988). We did
not collect data about the attitude towards dreaming or oth-
er motivational factors.
4.3. Location of stimulation
Concerning the location of tactile stimulation, we induced
two lucid dreams by stimulating the ankle in comparison to
no lucid dream when the stimulus was applied at the wrist
or index nger. Because of the overall small amount of lucid
dreams induced in each condition, no general conclusion
could be drawn here. It is possible that body parts which
are not as sensitive to touch as ngers or hands are more
likely to induce lucidity rather than awaken the person. In
western societies feet are not that important for tactile sen-
Table 3. Number of stimulus applications before participants
were awakened by stimulation or experimenter
Number of applications Study 1 Light Study 2 Vibration
One 5 (20.8%) 5 (20.8%)
Two 0 2 (8.3%)
Three 0 2 (8.3%)
Four 3 (12.5%) 4 (16.7%)
Five 16 (66.7%) 11 (45.8%)
Lucid dream induction by visual and tactile stimulation
International Journal of Dream Research Volume 7, No. 1 (2014)66
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sation, hence, tactile stimulation at the feet might lead to
fewer awakenings. This assumption should be examined in
future research.
4.4. Incorporation rate
We further wanted to investigate whether visual and tac-
tile stimuli are incorporated into participant’s dreams and
whether they trigger wakening responses. In our study the
incorporation rate was 39 % in the visual condition and
about 45 % in the tactile conditions, which almost reects
the results of earlier investigations: 23 % with light ashes
and about 48.2 % with tactile stimulation (see Schredl &
Stuck, 2009). It should be noticed that stimulations led to
high awakening rates of about 48 % in the tactile stimulation
conditions and 39% when using ashing lights. Compared
to previous incorporation and induction studies these rates
are rather high. The reason for this may be specic features
of our devices as well as other inuences of the lab environ-
ment. We suggest conducting pilot studies to test the incor-
poration qualities and awakening responses for certain (fea-
tures of) stimuli. For future induction studies it is advisable
to schedule an adaptation night in which the participant can
get used to the surrounding and devices and during which
individual awakening thresholds could be determined to ad-
just the intensity and timing of the stimuli.
4.5. Unfamiliarity with lucid dreaming
It should be considered that external stimulation in general
might not work well for participants unfamiliar with lucid
dreaming. For example, Price et al. (1986) suggested that
external stimulation might be more effective for enhancing
the lucid dream frequency of experienced lucid dreamers
than using it for beginners. Future studies should compare
external stimulation in frequent and non-frequent lucid
dreamers to further investigate this assumption.
Many studies contain no or only scarce information about
the sample; neither in terms of lucid dream experience nor
with respect to preceding training of participants (e.g. inten-
tions or suggestion). For comparison purposes, that infor-
mation would be desirable.
4.6. Time of stimulation
Moreover, the time of stimulus application, e.g. straight after
a REM burst, might inuence induction rates as well (Price
et al.,1986). In the present study the only criteria for stimula-
tion were to wait at least 5 minutes after REM onset before
starting stimulation and even longer when REMs stopped
between the 3rd and 5th minute of the REM period.
5. Conclusion
The results suggest that lucid dreams can be triggered by
visual or tactile stimulation. However, the frequencies of the
induced lucid dreams are – in comparison to earlier studies
– quite low. Furthermore, for tactile stimulation it seems im-
portant at which part of the body the stimulation is applied.
In general, the intensity of stimulation needs to be adjusted
because stimulation often led to an awakening of partici-
pants. Thus it seems important for future studies to focus
on factors like waking thresholds and preparation of par-
ticipants in order to minimize awakenings and to maximize
lucid dream induction.
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