Coping with Stress: The Effectiveness of Different Types of Music

Abstract

Listening to classical and self-selected relaxing music after exposure to a stressor should result in significant reductions in anxiety, anger, and sympathetic nervous system arousal, and increased relaxation compared to those who sit in silence or listen to heavy metal music. Fifty-six college students, 15 males and 41 females, were exposed to different types of music genres after experiencing a stressful test. Several 4 x 2 mixed design analyses of variance were conducted to determine the effects of music and silence conditions (heavy metal, classical, or self-selected music and silence) and time (pre-post music) on emotional state and physiological arousal. Results indicate listening to self-select or classical music, after exposure to a stressor, significantly reduces negative emotional states and physiological arousal compared to listening to heavy metal music or sitting in silence.

Full text

Coping with Stress: The Effectiveness of Different Types of Music
Elise Labbe
´
Æ Nicholas Schmidt Æ Jonathan Babin Æ
Martha Pharr
Published online: 27 October 2007
 Springer Science+Business Media, LLC 2007
Abstract Listening to classical and self-selected relaxing
music after exposure to a stressor should result in significant
reductions in anxiety, anger, and sympathetic nervous system
arousal, and increased relaxation compared to those who sit in
silence or listen to heavy metal music. Fifty-six college stu-
dents, 15 males and 41 females, were exposed to different
types of music genres after experiencing a stressful test.
Several 4 · 2 mixed design analyses of variance were con-
ducted to determine the effects of music and silence conditions
(heavy metal, classical, or self-selected music and silence) and
time (pre–post music) on emotional state and physiological
arousal. Results indicate listening to self-select or classical
music, after exposure to a stressor, significantly reduces neg-
ative emotional states and physiological arousal compared to
listening to heavy metal music or sitting in silence.
Keywords Stress  Anger  SNS arousal  Music types
Music may be a medium to help young people reduce
negative emotions. In reviewing the research literature one
finds a lack of scientific studies on the psychophysiological
effects of different types of music in young people. Music
is an important aspect of youth culture and most young
people listen to music for a variety of reasons (Trzcinski
1994). Young people report that music can help them relax
and will often have a collection of favorite ‘tunes’ that they
will listen to when they are feeling ‘stressed out’
(Knobloch and Zillman 2002). Burns et al. (1999, 2002)
and Labbe
´
et al. (2004) report findings that suggest
listening to relaxing music, such as some selections of
classical music, results in the listener experiencing positive
emotions and increases in parasympathetic nervous system
arousal. They observed participants’ reaction to what is
traditionally considered relaxing music and hypothesized
that an individual’s perception of whether they believed the
music was relaxing may be an important factor in inducing
relaxation. Self-selected music refers to music that the
participants chose as relaxing.
In the current study we evaluated music the person
believes is relaxing to determine whether listening to music
that one is attracted to can be an effective coping response
to negative emotion. Allowing the person to select music
gives them control over some aspect of the experimental
situation. Health psychology research indicates perceived
control is an important factor in reducing the stress
response (Brannon and Fiest 2007). Self-selected rather
than prescribed music may be more effective in reducing
stress as it allows the person to control some aspect of their
environment by allowing them to choose music that they
believe is relaxing.
In contrast to the effects of relaxing music, Anderson
et al. (2003) report on five experiments involving over 500
college students that examined the effects of seven violent
songs by seven artists and eight nonviolent songs by seven
artists. After listening to a music selection the college
student was given tasks to complete that measure aggres-
sive thoughts and emotions. The results indicated that
violent songs compared to nonviolent songs led to more
aggressive thoughts and feelings of hostility even when not
provoked. However, they did not measure physiological
arousal. Listening to soothing and relaxing music may play
an important role in reducing negative emotions and
increasing positive emotions and parasympathetic arousal.
However, some types of music may actually increase
E. Labbe
´
(&)  N. Schmidt  J. Babin  M. Pharr
Department of Psychology, University of South Alabama,
Mobile, AL 36688, USA
e-mail: elabbe@usouthal.edu
123
Appl Psychophysiol Biofeedback (2007) 32:163–168
DOI 10.1007/s10484-007-9043-9

negative emotions and sympathetic nervous system arou-
sal; this differential effect of music in young people has not
been adequately tested.
In previous studies we found mixed results regarding
changes in physiological responses, particularly with heart
rate (Burns et al. 1999, 2002; and Labbe
´
et al. 2004). In
these previous studies we used a plethysmograph placed on
the ventral side of the middle finger of the right hand to
measure heart rate. The plethysmograph was chosen over
placing electrodes on the chest because it was less invasive.
We discovered that the plethysmograph is very susceptible
to motion artifacts and is not as reliable a measure of heart
rate as using EKG electrodes placed on the chest. In the
current study we were able to measure heart rate using
EKG electrodes placed on the chest, with the hopes that we
would obtain more reliable heart rate data. A second
problem addressed in the current study was to allow the
participants to listen to music or sit in silence for a longer
period of time, 20 min instead of 10. And finally instead of
trying to increase arousal by telling the participants that
they would be engaging in a stressful test after listening to
music or sitting in silence, we actually administered the
stressful test prior to listening to music.
We hypothesized that individuals who are exposed to
classical music or self-selected relaxing music will demon-
strate significant reductions in anxiety, anger, and
sympathetic nervous system arousal, and an increase in
feelings of relaxation as compared to those who sit in silence
or listen to heavy metal music. Another hypothesis was there
would be a significant positive relationship with ratings of a
person’s use of music for relaxation and relaxation experi-
enced during the self-selected and classical music conditions.
Method
Participants
Fifty-six college students attending a southeastern univer-
sity participated (X age = 22.54), 15 males and 41
females—11% of the participants were African American;
82% were Caucasian, 2% were Asian and 2% were ‘other’
ethnicity. Participants received 5% grade credit in their
psychology courses for participation in the study. The
Institutional Review Board of the university approved the
study and the ethical standards of the American Psycho-
logical Association were upheld in conducting the study.
Measures and Apparatus
Measures included a demographic questionnaire, Relaxa-
tion Rating Scale (RRS), Music Rating Scale (MRS), State-
Trait Anger Expression Inventory-2 (STAIX-2), State-Trait
Anxiety Inventory-Form Y (STAI-Y) and physiological
assessment of heart rate, respiration and skin conductance.
A cognitive speed test was used to elicit sympathetic ner-
vous system arousal. Measures and apparatus are described
below.
The Relaxation Rating Scale (RRS) requires the par-
ticipant to rate his/her level of relaxation on a Likert-type
scale with 1 being ‘‘Not relaxed at all’’ and 7 being
‘‘Totally relaxed’’ by circling the number that best descri-
bed his/her level of relaxation. Higher scores indicated the
participant was more relaxed.
The State-Trait Anxiety Inventory (STAI) Form Y is a
40-item self-report survey. Twenty of the items require an
individual to rate how they feel ‘at this moment’; these
items make up the State Anxiety Scale. The other 20 items
require the individual to rate how they feel ‘generally’;
these items make up the Trait Anxiety Scale. Higher scores
indicate great levels of anxiety for both scales. Test–retest
correlations for the State Anxiety Scale range from .16 to
.62, and correlations for the Trait Anxiety Scale range from
.73 to .86. The relatively low test–retest correlations found
on the State Anxiety Scale are in keeping with the transi-
tory nature of the construct being measured (Spielberger
et al. 1983). The use of the STAI to validate other mea-
sures of state and trait anxiety supports its construct
validity (Corr and Gray 1996; Osman et al. 1997; Sapp
et al. 1997).
The State-Trait Anger Expression Inventory-2 (STAXI-
2) was used to measure state and trait anger. The STAXI-2
is a self-report survey, which scores experience of anger
along multiple axes: State and Trait Anger (S-Ang and
T-Ang) as well as Anger Control and Anger Expression.
The full STAXI-2 is a 57-item self-report instrument, with
six scales and five subscales (Spielberger 1999). Scores for
S-Ang and T-Ang are divided into S-Ang/F, S-Ang/V, and
S-Ang/P, etc. for feelings of anger, expression of anger
verbally, and physical expression of anger, respectively.
Also included in the full STAXI-2 is an Anger Expression
Index score, distinguishing Anger Expression In and Anger
Expression Out. The STAX-I has been demonstrated to
correlate ‘‘strongly’’ with the Buss-Durkee Hostility
Inventory and Overt Hostility scales of the MMPI (Spiel-
berger 1999) arguing for convergent validity.
A small testing room containing a recliner and two
speakers was used. A 40-W desk lamp softly lighted the
room. Heart rate was measured by placing EKG gel elec-
trodes on the chest, providing the best signal quality. The
negative lead was placed on the right shoulder, the positive
lead at the xphoid process and the ground lead on the left
shoulder. An abdominal placement for respiration was used
by strapping the respiration sensor’s Velcro fastener across
the participant, at the belly-button level with the rubber
164 Appl Psychophysiol Biofeedback (2007) 32:163–168
123

tube placed on the front. The strap was adjusted so that
there was a slight tension when the participant fully
breathed out. A second respiration sensor for thoracic
breathing was wrapped around the participant just below
the armpit level. Each electrode of the skin conductance
sensor was strapped around the finger pads of the index and
annular fingers. The electrodes were placed on the palm
side of the finger. Heart rate, respiration and skin con-
ductance were monitored using a Procomp+ encoder.
Leads for each monitor were routed through a Procomp+
encoder, and data was processed, observed and recorded
with the use of CardioPro 2.0 software. Please refer to the
Cardiopro
TM
, Version 2.0 Installation and User Manual for
more detailed technical information.
Physiological data was averaged over 5-min periods.
Data from the last 5 min of the ‘stress test’ was used to
assess the stress/pre-music period in order to achieve a
consistent baseline across participants. In order to achieve
a more valid indicator of the effects of the experimental
conditions, participants listened to music/silence for a
longer period (10 versus 20 min) than we had done in
previous studies and we used the data from the last 5 min.
We did this because immediately after completing the
‘stress test’ all participants experienced some reduction in
their physiological responses and we wanted to make sure
that the data we used to assess the experimental conditions
were not affected by just the relief from the stressor being
removed.
A brief, ‘‘cognitive speed test’’ was administered to
elicit sympathetic nervous system arousal, simulating a
negative stressor. The test took about 10 min and contained
80 simple calculations and 16 difficult mathematical
operations to be completed in 45 s, 8 number memory
items (9–10 string of single digits), 12 difficult verbal
analogies, and spelling 14 difficult words.
Two compact discs were used for the heavy metal and
classical selections. Each music selection was 20 min long.
A professor of music created the discs using music selec-
tions that met several parameters. For the classical CD, the
majority of the selections were in the Baroque style with
moderate to slow tempo markings, i.e. Andante, Adagio,
Largo. The crescendo and accelerando are not character-
istic to this style, so the tempo and dynamics remained
relatively constant throughout each track. Also, the selec-
tions were entirely instrumental, with strings as the
dominant musical timbre. In creating the Heavy Metal CD,
it was difficult to find works without vocals, and it was her
opinion that lyrics would divert the listener’s attention
from the task at hand, so the vocals on this CD are in
German, which was not the native language of any of the
subjects. Thus the listener is easily able to dismiss the
lyrics as containing any relevant content and they become
just another musical timbre. This CD also had consistent
tempi from track to track, much faster and the general
dynamic was much louder than that of the classical CD. In
this case, any crescendi or acceleration within a track were
allowable as the purpose of this collection was to agitate
the listener. In addition to the angst filled German vocals,
the instrumental timbres of electric guitar, heavy bass,
drums and electronica also served to grate on the con-
sciousness of the listener. The overall mix of each CD was
to create a wash of sound in its particular style that would
not contain any obvious climaxes or points of arrival.
Participants were instructed to bring a compact disc with
20 min of music that they believed was relaxing. Most
participants brought country music, soft jazz and easy lis-
tening rock music selections. Music was heard through
dynamic type stereo headphones and set at a volume level
that was approved by an audiologist.
Procedure
Participants were randomly assigned to self-selected,
classical, or heavy metal music conditions or silence.
Participants completed the demographic questionnaire and
trait scales and then physiological sensors were attached.
Baseline physiological data was recorded for 10 min.
Participants were administered a mentally challenging test
and then completed the state anxiety and anger scales and
Relaxation Rating Scale (RRS). They were told they would
either sit in silence or listen to music for 20 min. After
sitting in silence or listening to music they were again
given the state anxiety and anger scales, RRS and Music
Rating Scale. Physiological sensors were detached and then
the participants were debriefed.
Results
Several 4 · 2 mixed design analyses of variance with
repeated measures were conducted to determine the effects
of the music and silence conditions (heavy metal, classical,
or self-selected music and silence) and time (stress/pre
music, post-last 5 min of music/silence) on state anxiety
and anger scores, rating of relaxation, heart rate, respiration
and skin conductance. See Table 1 for means and standard
deviations for physiological variables. In order to test ini-
tial predictions, select t-tests were conducted even though
only a significant main effect was found. Furthermore, we
were interested in exploring not only statistically signifi-
cant differences but clinically significant differences as
well.
For state anxiety a significant Time · Music/Silence
interaction was present (F(3,50) = 3.74, p = .02). In addi-
tion the main effect for time was significant (F(1,50) = 7.93,
Appl Psychophysiol Biofeedback (2007) 32:163–168 165
123

p = .01). The main effect for music/silence condition was
not significant (F(3,50) = .93, p = .44). Post hoc paired-
sample t tests indicate that the groups listening to heavy
metal (t(12) = –1.01, p = .33) or silence (t(10) =
1.97, p = .07) did not experience a decrease in state anxiety;
where as participants listening to classical (t(15) =
3.07, p = .01) or self-selected music (t(13) = 3.27, p = .01)
experienced decreases in state anxiety, see Fig. 1.
For ratings of relaxation a significant Time · Music
interaction was present (F(3,46) = 3.52, p = .02). In addi-
tion the main effect for time was significant (F(1,46) =
63.54, p = .00). The main effect for music/silence condi-
tion was not significant (F(3,46) = 2.58, p = .06). Post hoc
paired-sample t tests demonstrate the group listening to
heavy metal did not have changes in ratings of relaxation
(t(10) = –1.00, p = .34) where as the groups listening to
silence(t(9) = –5.07, p = .00), classical (t(14) = –5.14,
p = .00) or self-selected (t(13) = –6.25, p = .00) music did
have increases in ratings of relaxation, refer to Fig. 2.
For state anger a significant main effect for time was
present (F(1,49) = 6.95, p = .01). The Time · Music/
Silence interaction was not significant (F(3,49) = 1.99,
p = .13). The main effect for music/silence condition was
not significant (F(3,49) = 1.94, p = .145). Post hoc paired-
sample t tests indicates that the group listening to silence
(t(10) = 3.53,
p = .00) or self-selected (t(12) = 3.41,
p = .00) music experienced more of a decrease in state
anger than participants listening to heavy metal (t(12) =
–.43, p = .67) or classical (t(15) = .60, p = .56), refer to
Fig. 3.
For heart rate a significant main effect for time was
present (F(1,50) = 4.96, p = .03). The Time · Music/
Silence interaction was not significant (F(3,50) = 1.21,
p = .35). The main effect for music/silence condition was
not significant (F(3,50) = .20, p = .98). Post hoc paired-
sample t tests indicate the listening to self-selected music
(t(13) = 4.56, p = .00) experienced a decrease in heart rate
where as participants listening to classical (t(15) = 1.48,
p = .16), heavy metal music (t(12) = .48, p = .64) or
silence (t(10) = .03, p = .99) did not.
For respiration a significant main effect for time was
present (F(1,50) = 7.22, p = .01). The Time · Music/
Silence interaction was not significant (F(3,50) = .74,
p = .53). The main effect for music/silence condition was
not significant (F(3,50) = 1.78, p = .16). Post hoc paired-
sample t tests indicates the group listening to classical
(t(14) = 2.36, p = .03) and heavy metal (t(13) = 2.42,
p = .03) music experienced lower respiration rates than
participants listening to self-selected (t(13) = 1.25,
p = .23) or silence (t(10) = .06, p = .95).
For skin conductance a significant main effect for time
was present (F
(1,46) = 46.85, p = .00). The Time · Music/
Table 1 Means and standard deviations for heart rate, respiration and
skin conductance for stress and music or silence conditions
Physiological measures Stress X (SD) Music/Silence X (SD)
Heart rate
Silence 82.47 (8.24) 82.31 (19.24)
Heavy metal 86.12 (9.88) 84.32 (12.99)
Classical 89.66 (10.91) 82.61 (24.25)
Self-select 89.13 (11.35) 79.39 (11.94)
Respiration
Silence 35.57 (7.84) 35.46 (9.99)
Heavy metal 36.10 (10.88) 33.49 (12.65)
Classical 30.05 (7.56) 27.52 (6.55)
Self-select 36.62 (9.58) 34.98 (11.19)
Skin-conductance
Silence 3.84 (2.10) 2.92 (2.11)
Heavy metal 4.14 (1.73) 3.45 (1.55)
Classical 4.71 (2.57) 3.11 (2.15)
Self-select 5.23 (2.28) 3.16 (1.80)
38
40
42
44
46
48
50
52
54
Silence Self-Select Heavy Metal Classical
Music Groups
yteix
nA et
atS
Pre Music
Post Music
Fig. 1 State anxiety scores, pre music (stress) and post music or
silence
0
1
2
3
4
5
6
7
Silence Self-Select Heavy Metal Classical
Music Groups
sgnitaR noitaxaleR
Pre Music
Post Music
Fig. 2 Relaxation ratings of pre music (stress) and post music or
silence
166 Appl Psychophysiol Biofeedback (2007) 32:163–168
123

Silence interaction was also significant (F(3,46) = 2.84,
p = .05). The main effect for music/silence condition was
not significant (F(3,46) = .39, p = .76). Post hoc paired-
sample t tests indicated that all groups experienced a sig-
nificant decrease in skin conductance: classical (t(13) =
5.38, p = .00), self-selected music (t(11) = 3.61, p = .00),
heavy metal (t(12) = 3.07, p = .01) and silence (t(10) =
2.15, p = .047).
A significant Pearson Product Moment Correlation,
r = .52, p = .00 with ratings of use of music for relaxation
and how much they liked the self-selected or classical
music was found, but not with relaxation experienced
during the self-selected and classical music condition,
r = .24, p = .21.
Discussion
The results of our study support the hypothesis that indi-
viduals who are exposed to classical music or self-selected
relaxing music after exposure to a stressor will demonstrate
significant reductions in state anxiety and an increase in
feelings of relaxation as compared to those who sit in silence
or listen to heavy metal music. Listening to self-selected and
classical music produced increased feelings of relaxation as
well as sitting in silence but not for the heavy metal condi-
tion. Listening to classical and self-selected music elicited
reductions in state anxiety after exposure to a stressor.
Interestingly, those participants who listened to heavy metal
music not only experienced greater levels of state anxiety
but were even more anxious after listening to the heavy
metal music than when they were being stressed.
State anger scores decreased significantly over time for
all participants. However, post hoc t tests indicated that
listening to self-select music resulted in the lowest rating of
state anger as compared to the other conditions. Note-
worthy is that although all groups demonstrated some
decrease in state anger scores the self-select group dem-
onstrated the most ‘clinical’ change as scores decreased
from a mean of 50 to a mean of 39 as compared to the high
40s for the other groups. The self-select condition may
foster feelings of personal control as the individual is
allowed to listen to music that they chose as relaxing. This
finding is consistent with research on perceived control and
its relationship to feelings of anger and irritability.
Heart rate and respiration decreased over time, regard-
less of the music/silence condition. Post hoc t tests suggest
that participants in the self-select and classical music con-
ditions experienced greater reductions in heart rate after
being stressed than the other groups. Interestingly, respi-
ration decreased the most for the classical and heavy metal
music conditions. These results are consistent with previous
studies that we have conducted in that although some
changes in physiological arousal were found they were not
as significantly altered compared to participants’ report of
their emotional state. For example, participants in the heavy
metal condition reported increases in anxiety and anger and
little change in their feelings of relaxation, however, their
physiological arousal as measured by skin conductance and
respiration did decrease over time, although not as much as
the other groups. Listening to music may affect the emo-
tional and cognitive experience of an individual more than
their physiological arousal. However, participants listening
to their own music demonstrated greater consistency in self-
report of emotions and changes in physiological arousal as
five out of the potential six responses (stage anger and
anxiety, relaxation, heart rate, skin conductance and respi-
ration) were significantly changed compared to the other
groups. Those listening to classical music demonstrated
changes in four of the six responses, sitting in silence
resulted in changes of three responses and listening to heavy
metal only resulted in reductions of two responses (skin
conductance and respiration).
We did not find a significant positive relationship with
ratings of a person’s use of music for relaxation and
relaxation experienced during the self-selected and classi-
cal music conditions. One reason that the correlation may
have not been significant was the participants who listened
to self-select and classical music had a mean relaxation
rating of 6.45 (SD = 1.05) out of 7, indicating a very
homogenous response. Therefore there was not enough
variability in their ratings of relaxation for a significant
correlation to occur. However, participants’ report of how
frequently they used music to relax was related to greater
ratings of liking classical or select selected music.
0
10
20
30
40
50
60
70
Silence Self-Select Heavy Metal Classical
Music Groups
t
StaA e
ng
er
Pre Music
Post Music
Fig. 3 State anger scores pre (stress) and post music or silence
Appl Psychophysiol Biofeedback (2007) 32:163–168 167
123

A concern with this study is that the participants were
college students and findings might not be appropriately
generalized to other groups of individuals. We did find that
measuring heart rate using EKG sensors placed on the chest
provided a more reliable measure than using a plethysmo-
graph on the finger. Thus we are more confident in the
results of the current study. Actually stressing the partici-
pants prior to listening to the music created a better measure
of the participants feeling stressed as it resulted in a greater
range of emotional and physiological responses that could
be potentially affected by the experimental conditions.
Extending the time listening to music or sitting in silence
allowed us to be more confident that changes over time was
related to the experimental condition rather than just feeling
less stressed because the stress test was over.
In conclusion, listening to some types of music genres
elicit positive emotional and cognitive states, and reduces
sympathetic nervous system arousal compared to sitting in
silence or listening to heavy metal music. Therefore, lis-
tening to self-selected or classical music might be useful as
a stress management strategy, especially if an individual is
unwilling to sit in silence for a long enough time to achieve
a relaxation response.
Acknowledgment This project was supported by Grant # 2001-SI-
FX-0006 awarded by the Office of Juvenile Justice and Delinquency
Prevention, Office of Justice Programs, U.S. Department of Justice.
References
Anderson, C. A., Carnagey, N. L., & Eubanks, J. (2003). Exposure to
violent media: the effects of songs with violent lyrics on
aggressive thoughts and feelings. Journal of Personality and
Social Psychology, 84, 4, 960–971.
Brannon, L., & Fiest, J. (2007). Health psychology: An introduction to
behavior and health, 6th edn. Belmont: Thomson-Worth.
Burns, J. L., Labbe
´
, E., Arke, B., Capeless, K., Cooksey, B.,
Steadman, A., & Gonzales, C. (2002). The effects of different
types of music on perceived and physiological measures of
stress. Journal of Music Therapy, 28, 104–116.
Burns, J. L., Labbe
´
, E., Williams, K., & McCall, J. (1999). Perceived
and physiological indicators of relaxation: As different as
Mozart and Alice in Chains. Applied Psychophysiology and
Biofeedback, 24, 197–202.
Corr, P. J., & Gray, J. A. (1996) Structure and validity of the
attributional style questionnaire: A cross-sample comparison.
The Journal of Psychology, 130, 645–647.
Knobloch, S., & Zillman, D. (2002) Mood management via the digital
jukebox. Journal of Communication, June, 351–366.
Labbe
´
, E., Booth, K., Jimerson, M., & Kawamura, N. (2004). The
sound of music: Evaluating responses to different music genres,
to be presented at the annual meeting of the Southeastern
Psychological Association, Atlanta, GA, March.
Osman, A., Kopper, B. A., Barrios, F. X., Osman, J. R., & Wade, T.
(1997). The Beck anxiety inventory: Reexamination of factor
structure and psychometric properties. Journal of Clinical
Psychology, 53, 7–14.
Sapp, M., Farrell, W. C., Johnson, J. H., & Ioannidis, G. (1997).
Utilizing the PK scale of the MMPI-2 to detect y
¨
osttraumatic
stress disorder in college students. Journal of Clinical Psychol-
ogy, 53, 841–846.
Spielberger, C. D. (1999). STAXI-2 state-trait anger expression
inventory-2 professional manual. Lutz: Psychological Assess-
ment Resources, Inc.
Spielberger, C. D., Gorsuch, R. L., Lushene, R., Vagg, P. R., & Jacobs,
G. A. (1983). Manual for the state-trait anxiety inventory: Form
Y. Palo Alto: Consulting Psychologists Press, Inc.
Trzcinski, J. (1994) Today’s music: Poetry or pornography? Correc-
tions Today, 56(7), 148.
168 Appl Psychophysiol Biofeedback (2007) 32:163–168
123