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15
Intern. J. Neuroscience, 113:15–38, 2003
Copyright 2003 Taylor & Francis
0020-7454/03 $12.00 + .00
DOI: 10.1080/00207450390161903
AROMAS OF ROSEMARY AND LAVENDER
ESSENTIAL OILS DIFFERENTIALLY
AFFECT COGNITION AND MOOD
IN HEALTHY ADULTS
MARK MOSS
JENNY COOK
Human Cognitive Neuroscience Unit
Division of Psychology
University of Northumbria
Newcastle upon Tyne, UK
KEITH WESNES
Human Cognitive Neuroscience Unit
Division of Psychology
University of Northumbria
Newcastle upon Tyne, UK
Cognitive Drug Research
CDR House
Portman Road
Reading, UK
PAUL DUCKETT
Human Cognitive Neuroscience Unit
Division of Psychology
University of Northumbria
Newcastle upon Tyne, UK
Received 24 July 2002.
Address correspondence to Dr. Mark Moss, Human Cognitive Neuroscience Unit, Division of
Psychology, Northumberland Building, University of Northumbria, Newcastle upon Tyne, NE1
8ST, UK. E-mail: mark.moss@unn.ac.uk
16 M. Moss et al.
This study was designed to assess the olfactory impact of the essential
oils of lavender (Lavandula angustifolia) and rosemary (Rosmarlnus
officinalis) on cognitive performance and mood in healthy volunteers.
One hundred and forty-four participants were randomly assigned to one
of three independent groups, and subsequently performed the Cognitive
Drug Research (CDR) computerized cognitive assessment battery in a
cubicle containing either one of the two odors or no odor (control).
Visual analogue mood questionnaires were completed prior to exposure
to the odor, and subsequently after completion of the test battery. The
participants were deceived as to the genuine aim of the study until the
completion of testing to prevent expectancy effects from possibly influ-
encing the data. The outcome variables from the nine tasks that consti-
tute the CDR core battery feed into six factors that represent different
aspects of cognitive functioning. Analysis of performance revealed that
lavender produced a significant decrement in performance of working
memory, and impaired reaction times for both memory and attention
based tasks compared to controls. In contrast, rosemary produced a
significant enhancement of performance for overall quality of memory
and secondary memory factors, but also produced an impairment of
speed of memory compared to controls. With regard to mood, compari-
sons of the change in ratings from baseline to post-test revealed that
following the completion of the cognitive assessment battery, both the
control and lavender groups were significantly less alert than the rose-
mary condition; however, the control group was significantly less con-
tent than both rosemary and lavender conditions. These findings indi-
cate that the olfactory properties of these essential oils can produce
objective effects on cognitive performance, as well as subjective effects
on mood.
Keywords aromatherapy, attention, lavender, memory, odor, rosemary
Despite the prevailing wisdom that the sense of olfaction may be a
vestige of our evolutionary past, the use of aromas to modulate
affect and mood has been reported since the beginnings of written
language, and is a widely continued practice today. The use of arti-
ficially introduced ambient odors in public places such as offices,
retail outlets, and hotel lobbies is widespread, as are the purported
subjective psychological benefits of the odors themselves (Jellinek,
1997). The use of aromatherapy as a therapeutic treatment for affec-
tive disorders has also widely reported in historical anecdotal litera-
ture (Valnet, 2000), and referred to in herbal medical texts (Bartram,
1995). Though due to the lack of a suitable placebo, until recently
little or no clear empirical evidence was available to support such
claims (Diego et al., 1998). However, it is interesting to note that
Essential Oils, Cognition, and Mood 17
Ballard and colleagues (Ballard et al., in press) reported the first
double-blind clinical trial to demonstrate improvements in agitation
levels in severe dementia patients following aromatherapy with Melissa
(lemon balm).
The essential oils used in aromatherapy are highly concentrated
essences extracted from plants through the process of distillation.
Although synthetic analogues of a number of the components of
these essential oils are commercially available, they are considered
inferior to the natural products by herbal medicine practitioners (Price,
1995). Each essential oil is believed to produce reliable and predict-
able effects on psychological state when inhaled (Sanderson & Ruddle,
1992), and a number of studies have investigated this possibility.
The reputed sedative nature of lavender has consistently been dem-
onstrated through the relief of anxiety and tension, and improve-
ments of mood (Lorig & Schwartz, 1987b; Ludvigson & Rottman,
1989; Buchbauer et al., 1991). Similar subjective relaxing effects
have been found for spiced apple (Schwartz et al., 1986b) and sandal-
wood (Steiner, 1994). The presence of such effects has further been
established by physiological and electrophysiological measurements.
Diego and colleagues (Diego et al., 1998) studied electroencephalo-
grams (EEGs) and found lavender inhalation to be associated with
increased beta power, which is acknowledged as being associated
with sedation. In addition, the contingent negative variation (CNV)
variable of EEG has been shown to be diminished by both lavender
and sandalwood oils, a finding consistent with decreased arousal
(Torii & Fukuda, 1985; Torii et al., 1988). By comparison, pepper-
mint, jasmine, and rosemary have been demonstrated to possess
subjectively stimulating or arousing properties (Warm & Dember,
1990; Kovar et al., 1987; Diego et al., 1998). These effects, as well
as being in line with reputation, have also subsequently been sup-
ported by results from physiological and electrophysiological mea-
surements that contrast those outlined above for sedating oils (Kubota
et al., 1992; Parasuraman et al., 1992; Sugano, 1992).
It is a possibility that changes in subjective state brought about
by aroma inhalation, and in particular changes in arousal and alert-
ness, may impact upon cognitive performance. Indeed arousal has
been demonstrated to interact with task demands, producing an in-
verted-U performance versus arousal curve (Yerkes & Dodson, 1908).
18 M. Moss et al.
A small number of studies that have attempted to investigate any
possible influence of aromas on cognition have produced equivocal
results, however. Diego et al. (1998) found the subjective mood and
EEG effects for both lavender (sedating) and rosemary (arousing)
as predicted. While both aromas improved the speed of maths com-
putations, only lavender increased accuracy. Similarly, Warm and
colleagues (Warm et al., 1991) reported that both arousing (pepper-
mint) and relaxing (muguet) aromas produced significant increases
in sensitivity on a visual sustained attention task compared to no
odor controls. Why these two aromas did not produce contrasting
effects on performance is not clear, but neither odor led to a subjec-
tive experience of the task being less taxing than in the control
condition. It may be that the impact of the aromas on task perfor-
mance was independent of subjective feelings. Degel and Köster
(1999) reported fewer errors on both letter counting and mathe-
matical tasks following inhalation of lavender compared to jasmine.
Furthermore, both odors led to significantly poorer performance on a
creativity task compared to no odor controls. By comparison, Ludvigson
and Rottman (1989) found lavender to impair arithmetic reasoning,
but not memory, when compared to cloves, with no concomitant
effect on mood for either odor. Ilmberger and colleagues (Ilmberger
et al., 2001) reported no clear influence of either peppermint, jas-
mine, ylang-ylang, or l,8-cineole (the major constituent of rosemary
oil) on speed on a psychomotor task. Rather, they reported complex
correlations between subjective evaluations and objective perfor-
mance, and suggested that the influences of odor on the basic forms
of attention are mainly psychological.
Interestingly, studies have also investigated situations where the
expectation of an ambient odor is produced in participants but when
none is actually presented (Knasko et al., 1990; Gilbert et al., 1997).
Furthermore, the participants were misled into believing that the
feigned odor would affect cognitive performance. However, the ob-
jective test data demonstrated no differences to exist between the
conditions, indicating that expectancies may be secondary to the
effect of any actual odor presented.
Previous research has therefore produced mixed findings regard-
ing the possible influence of aromas on cognitive performance. Dif-
ferences in methodology and the types of tasks employed have also
Essential Oils, Cognition, and Mood 19
made it difficult to compare results across studies. The current study
therefore aimed to definitively assess performance on a wide range
of tasks relating to a number of established cognitive domains. To
this end, the Cognitive Drug Research (CDR) battery was employed.
The CDR battery has been used in over 200 phase 1 and phase 2
clinical trials world-wide, and has been demonstrated to be reliable,
valid, and sensitive to changes in cognitive function (Wesnes et al.,
1999; Moss et al., 1998; Scholey et al., 1999). Participants perfor-
mance on the test battery was compared across conditions of ambi-
ent rosemary aroma, ambient lavender aroma, or no odor (control).
Subjective mood state was also assessed príor to and after the ex-
perimental session to investigate the possible interaction of cogni-
tive task performance and odor inhalation on ratings of calmness,
contentedness, and alertness.
MATERIALS AND METHODS
Participants
One hundred and forty-four undergraduates and members of the
general public volunteered to take part in this study. The composi-
tion of the three experimental groups consisted of the follow-
ing: rosemary condition: 28 females (mean age 25.3 years, SD 6.9),
20 males (mean age 24.5 years, SD 7.8); lavender condition: 27
females (mean age 23.8, SD 6.3); 21 males (mean age 24.7, SD
6.7); control condition: 30 females (mean age 24.9, SD 5.6),
18 males (mean age 26.2 SD 8.1). Prior to participation each volun-
teer completed a health questionnaire. All participants self-reported
that they were in good health and none were excluded from the
study.
Aromas
“Tisserand” pure essential oils (Tisserand Aromatherapy, Newtown
Road, Hove, Sussex, UK) of lavender and rosemary were used to
produce the ambient aromas. Four drops of the appropriate oil (or
water in the control condition) were applied to a diffuser pad for a
20 M. Moss et al.
“Tisserand Aroma-stream.” The Aroma-stream was placed under
the bench in the testing cubicles so as to be out of sight, and switched
on for 5 min prior to the testing of each participant. Each aroma
was above detection threshold and of approximately equivalent strength
for each testing session as assessed by an independent party.
Testing Cubicles
Each testing cubicle measured 2.4 m long × 1.8 m wide × 2.4 m
high and were maintained at a temperature between 18 and 22 de-
grees Celsius throughout the testing sessions.
Cognitive Measures
A tailored version of the Cognitive Drug Research (CDR) comput-
erized assessment system (installed on Viglen genie computers) was
employed to evaluate cognitive performance. The CDR system in-
cludes a number of measures that are specific to particular aspects
of attention, working memory, and long-term memory. Stimuli are
presented on a color monitor, and (with the exception of word re-
call) responses are made using a simple response module containing
two buttons labeled “Yes” and “No,” respectively. A suite of pro-
grams controls all aspects of testing, including selection of appro-
priate sets of stimuli for presentation and recording all responses.
The tests employed in this study were presented in the following
order:
Word presentation. A series of 15 words were presented sequen-
tially for 1 s, each with an interstimulus interval of 1 s. The
words were a mix of one, two, and three syllables.
Immediate Word Recall. The computer display counted down 60 s,
during which time participants wrote down as many of the words
from the list as possible. Recall was scored for number of correct
words and errors (words not presented in the list).
Picture Presentation. Twenty photographs were presented, with a
stimulus duration of 2 s each, and interstimuli interval of 1 s.
Simple Reaction Time. The word Yes was presented in the center of
the screen. The participant had to press the Yes button as quickly
Essential Oils, Cognition, and Mood 21
as possible. There were 50 trials, and the intertrial interval varied
randomly between 1 and 2.5 s. The reaction time was recorded in
ms.
Digit Vigilance. A number was displayed constantly to the right of
the screen. A series of 240 digits was presented one at a time in
the center at a rate of 80 per min; 45 matched the constantly
displayed digit. The participant had to press the Yes button as
quickly as possible every time the digit in the center matched the
one constantly displayed. Accuracy of response (%), reaction time
(ms), and number of false alarms were recorded.
Choice Reaction Time. Either the word Yes or No was presented in
the center of the screen. The participant had to press the Yes or
No button as appropriate and as quickly as possible. There are 50
trials (25 “Yes” and 25 “No”), and the intertrial interval varied
randomly between 1 and 2.5 s. Accuracy (%) and reaction time
(ms) were recorded.
Spatial Working Memory. A schematic picture of a house was pre-
sented for 5 s. The house had nine windows in a 3 × 3 pattern,
four of which were illuminated. A series of 36 presentations of
the same house in which just one window was illuminated fol-
lowed, and the participant had to respond Yes if the window was
one of the four lit in the original presentation, or No if it was not.
Sixteen of the stimuli required a Yes response and 20 a No re-
sponse. Reaction time and accuracy were recorded and a sensi-
tivity index was calculated.
Memory Scanning. Five digits were presented singly at the rate of
1 every s for the participant to remember. A series of 30 digits
was then presented. For each, the participant must press Yes or
No according to whether the digit was thought to be one of the
five presented initially. Fifteen stimuli required a Yes response
and 15 a No response. This was repeated three times using a
different 5 digits on each occasion. Reaction time was recorded
and a sensitivity index calculated.
Delayed Word Recall. The computer counted down 60 s, during
which time participants free-recalled as many of the words from
the list as possible. Recall was scored as the number of correct
words, and errors (words not presented in the list).
Word Recognition. The 15 words initially presented for the word
22 M. Moss et al.
recall were presented again in random order, interspersed with 15
new words. The participant pressed Yes or No each time to sig-
nal whether or not the word was from the original list. Reaction
time and accuracy were recorded and a sensitivity index was
calculated.
Picture Recognition. The 20 pictures presented earlier were shown
again in random order, interspersed with 20 similar new ones.
The participant signaled recognition by pressing the appropriate
Yes or No button. Reaction time and accuracy were recorded,
and a sensitivity index calculated.
“Pencil and Paper” Visual Analogue Scales. Subjective levels of
alertness, calmness, and contentedness were presented prior to
and following the computerized tests. Participants were required
to indicate their current state by marking a line drawn between
two bipolar adjectives. The entire battery took approximately 25
min to administer.
Primary Cognitive Outcome Measures
The above measures were collapsed into four global outcome fac-
tors, and two subfactors derived from the battery by factor analysis,
as previously utilized (Kennedy et al., 2000, 2001; Wesnes et al.,
1997, 2000).
Quality of memory. This was derived by combining the percentage
accuracy scores (adjusted for proportions of novel and new stimuli
where appropriate) from all of the working and secondary memory
tests: spatial working memory, numeric working memory, word
recognition, picture recognition, immediate word recall, and de-
layed word recall (with adjustments to the total percentage
correct for errors on the latter two tasks). A 100% accuracy across
the six tasks generated a maximum score of 600 on this index.
Examination of the factor pattern suggests that this global “quality
of memory” factor can usefully be further divided into two sub-
factors: “working memory” and “secondary memory”
Working memory subfactor. This was derived by combining the percentage
accuracy scores from the two working memory tests: spatial working
memory and numeric working memory. One hun-dred percent
Essential Oils, Cognition, and Mood 23
accuracy across the two tasks generated a maximum score of 200
on this index.
Secondary memory subfactor. This was derived by combining the
percentage accuracy scores (adjusted for proportions of novel and
new stimuli where appropriate) from all of the secondary memory
tests: word recognition, picture recognition, immediate word re-
call, and delayed word recall (with adjustments to the total per-
centage correct for errors on the latter two tasks). One hundred
percent accuracy across the four tasks generated a maximum score
of 400 on this index.
Speed of memory. This was derived by combining the reaction times
of the four computerized memory tasks: numeric working memory,
spatial memory, delayed word recognition, and delayed picture
recognition (units are summed ms for the four tasks).
Speed of attention. This was derived by combining the reaction times
of the three attentional tasks: simple reaction time, choice reaction
time, and digit vigilance (units are summed ms for the three tasks).
Accuracy of attention. This was derived by calculating the com-
bined percentage accuracy across the choice reaction time and
digit vigilance tasks with adjustment for false alarms from the
latter test. One hundred percent accuracy across the two tasks
would generate a maximum score of 100.
The contribution of individual task measures to each of these
factors and subfactors is illustrated schematically in Figure 1.
Subjective Mood Measure
The Bond-Lader visual analogue scales (Bond & Lader, 1974). The
16 visual analogue scales of Bond-Lader were combined as recom-
mended by the authors to form three mood factors: “alert,” “calm,”
and “content.”
Procedure
Participants were approached individually and asked if they would
help in the validation of a new cognitive test battery. No mention of
aromatherapy or essential oils was made. This deception was carried
24 M. Moss et al.
out in order to avoid the possibility of expectancy effects contami-
nating the data. Recruitment took place one week prior to testing,
and participants were randomly and unknowingly allocated to one
of the three conditions: lavender, rosemary, or no odor (control).
They were then given a time and day on which to attend the labora-
tory. Testing took place in three different cubicles, and on three
different days of the week (Monday, Wednesday, and Friday) to
avoid cross contamination of odors. On arrival at the lab, each par-
ticipant was once again reminded that he or she was there to assist
in the validation of the new test battery and to try his or her best on
FIGURE 1. Schematic representation of the CDR battery showing (from left to right)
running order of tasks, individual task outcome measures, and the composition of the
four factors derived by factor analysis. Arrows indicate that a task outcome measure con-
tributes to the given factor “Speed of Attention,” “Accuracy of Attention,” “Quality of
Memory,” or “Speed of Memory.” Dotted lines indicate contribution to both “Quality
of Memory” and to either “Working Memory” (-.-) or “Secondary Memory” (- - -), re-
spectively.
Essential Oils, Cognition, and Mood 25
all the tasks. Participants were then asked to complete the mood
scales, supposedly to assess if the tasks affected mood. Participants
were then taken into the cubicle where they completed the CDR
battery followed by a second mood scale. Finally, they were de-
briefed regarding the true nature of the experiment, and any ques-
tions answered. If any of the participants commented on the pres-
ence of an odor prior to or during the testing session, the researcher
dismissed it with responses of the kind: “nothing to do with me”
and “don’t know where it came from.” No participants indicated at
any time that they felt the odor had affected them at all, or that they
thought the study was investigating the effect of odor on perfor-
mance or mood.
Statistics
Scores from the individual task outcome measures were combined
to form the four global outcome measure factor scores, as well as
the secondary memory and working memory factor scores. These
and the individual task outcome measures making up the factors
were analyzed using the statistical package Minitab 12 for Win-
dows. The one-way analysis of variance (ANOVA) followed by
Tukey pairwise comparisons were employed to identify where any
differences between the three conditions may have existed. Analysis
of subjective mood was made in a similar manner on the pre- to
post-testing difference scores, reflecting any changes in mood state
due to exposure to the aromas and/or as a result of completing the
assessment battery.
RESULTS
The analyses of the individual task outcome measures that make up
the factors are presented in Table 1. The results described here con-
centrate on the primary cognitive outcome measures described above.
Quality of Memory Factor
An independent groups ANOVA revealed a significant differ-
ence between groups, F(2,141) = 4.80; p = .010. Tukey post-hoc
26 M. Moss et al.
TABLE 1. Effects of rosemary and lavender essential oils on individual task outcome
measures from the CDR battery
Outcome 1) Control 2) Rosemary 3) Lavender Significant
variable Mean ± SD Mean ± SD Mean ± SD comparisons
Immediate Word 5.47 ± 1.82 6.18 ± 2.03 5.54 ± 2.16
Recall Correct
Immediate Word 0.42 ± 0.65 0.30 ± 0.58 0.64 ± 1.02
Recall Errors
Simple Reaction 245.97 ± 14.12 249.43 ± 31.32 259.36 ± 36.35
Time
Number Vigilance 94.17 ± 9.79 90.69 ± 12.05 91.94 ± 9.12
Accuracy
Number Vigilance 1.04 ± 0.94 1.04 ± 1.52 0.92 ± 1.16
False Alarms
Number Vigilance 372.62 ± 32.34 375.87 ± 39.73 380.11 ± 46.05
Reaction Time
Choice Reaction 393.34 ± 49.39 402.52 ± 62.70 431.62 ± 83.61 1 vs 3*
Time
Spatial Memory 0.91 ± 0.10 0.89 ± 0.18 0.79 ± 0.26 1 vs 3*,
Sensitivity Index 2 vs 3*
Spatial Memory 824.5 ± 166.9 1043.8 ± 405.8 964.4 ± 326.5 1 vs 2**
Reaction Time
Numerical 0.83 ± 0.13 0.82 ± 0.16 0.75 ± 0.28
Working Memory
Sensitivity Index
Numerical 705.5 ± 137.5 782.4 ± 170.8 762.6 ± 161.3 l vs 2*
Working Memory
Reaction Time
Delayed Word 3.67 ± 2.03 4.28 ± 2.80 3.21 ± 2.70
Recall Correct
Delayed Word 0.42 ± 0.77 0.52 ± 1.05 0.69 ± 0.97
Recall Errors
Word Recognition 0.57 ± 0.16 0.65 ± 0.17 0.53 ± 0.31
Sensitivity Index 2 vs 3*
Word Recognition 772.8 ± 209.5 802.8 ± 173.5 929.3 ± 298.5 1 vs 3*,
Reaction Time 2 vs 3*
Picture Recognition 0.62 ± 0.23 0.69 ± 0.17 0.69 ± 0.16
Sensitivity Index
Picture Recognition
Reaction Time 826.7 ± 128.5 875.8 ± 186.9 909.3 ± 177.3
Note. The units are number of correctly recalled items for the word recall tasks, ms for the reaction
times. The sensitivity indices are calculated using the nonparametric signal theory index (SI) presented
by Frey and Colliver (1973). *p < .05; **p < .01.
Essential Oils, Cognition, and Mood 27
comparisons identified that the rosemary condition (mean = 363.91)
produced significantly higher scores than the lavender condition (mean
= 326.61), p < .05 (Figure 2a). No other significant differences were
found.
Secondary Memory Subfactor
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 4.44; p = .014. Tukey post-hoc com-
parisons identified that the rosemary condition (mean = 200.03)
produced significantly higher scores than the lavender condition
(mean = 174.24), and the control condition (mean = 176.60), p <
.05 in each case (Figure 2b). No other significant differences were
found.
FIGURE 2. Effects of rosemary and lavender on the cognitive factors derived from the
CDR test battery: (a) “Quality of Memory,” (b) “Secondary Memory,” (c) “Working Memory,”
(d) “Speed of Attention,” and (e) “Speed of Memory” (see text for details). Figures depict
mean values. Error bars represent standard deviations. *p < .05; **p < .01.
28 M. Moss et al.
Working Memory Subfactor
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 5.40; p = .006. Tukey post-hoe com-
parisons identified that both the rosemary condition (mean = 169.92)
and the control condition (mean = 172.74) produced significantly
higher scores than the lavender condition (mean = 152.37), p < .05
and <.01, respectively (Figure 2c). No other significant differences
were found.
Speed of Memory Factor
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 6.38; p = .002. Tukey post-hoc com-
parisons identified that the control condition (mean = 3129.5 ms)
produced significantly quicker responses than both the lavender con-
dition (mean = 3565.5 ms) and the rosemary condition (mean =
3504.7 ms), p < .0l and <.05, respectively (Figure 2d). No other
significant differences were found.
Speed of Attention Factor
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 3.57; p = 031. Tukey post-hoc com-
parisons identified that the control condition (mean = 1013.9 ms)
produced significantly quicker responses than the lavender condi-
tion (mean = 1071.1 ms), p < .05 (Figure 2e). No other significant
differences were found.
Accuracy of Attention Factor
An independent groups ANOVA revealed no significant differences
between groups, F(2,141) = 1.20; p = .305.
Subjective Mood Measures
Analysis of the pre-test ratings indicated no differences between the
three conditions on any of the mood variables prior to the experi-
mental session: Alertness, F(2,141) = 0.87; p = .422. Contented-
Essential Oils, Cognition, and Mood 29
ness, F(2,14l) = 1.18; p = .311. Calmness, F(2,141) = 0.52; p =
.594. Subsequent analyses compared post-test minus pre-test change
in mood scores.
Alertness
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 5.43; p = .005. Tukey post-hoc com-
parisons identified that the rosemary condition produced an increase
in alertness (mean change = 5.51), compared to decreases for both
the control condition (mean change = –3.06), p < .05, and the lav-
ender condition (mean change = –7.49), p < .01 (Figure 3a). No
other significant differences were found.
Contentedness
An independent groups ANOVA revealed a significant difference
between groups, F(2,141) = 9.72; p = .0001. Tukey post-hoc
comparisons identified that the rosemary condition produced an in-
crease in contentedness (mean change = 2.39) compared to controls
(mean change = –9.58), p < .01. In addition, the lavender condition
produced a decrease in contentedness (mean change = –2.79) that
was significantly less than that for the control condition (mean
change = –9.58), p < .05 (Figure 3b). No other significant differ-
ences were found.
Calmness
An independent groups ANOVA revealed no significant differences
between groups, F(2,141) = 0.73; p = .481.
DISCUSSION
The results of this study clearly support previous work indicating
that essential oils can influence mood (Roberts & Williams, 1992;
Buchbauer et al., 1991; van Toller & Dodd, 1988). More impor-
tant, we have demonstrated that the inhalation of ambient aromas of
30 M. Moss et al.
essential oils can significantly affect aspects of cognitive perfor-
mance. Further, due to the design employed in this study and the
deliberate diversion of participants attention away from the odors,
these effects are considered to be irrespective of participants expec-
tations or beliefs.
The changes in mood recorded over the period of the cognitive
testing can, to some extent, be matched to the objective test out-
FIGURE 3. Effects of rosemary and lavender on change in self-rated mood as measured
using the Bond-Lader Visual Analogue Scales: (a) “Alertness” and (b) “Contentedness.”
Figures depict mean change (post-test minus pre-test ratings), such that a positive change
represents an increase on that dimension over the test session. Error bars represent stan-
dard deviations. *p < .05; **p < .01.
Essential Oils, Cognition, and Mood 31
comes. Lavender essential oil is widely considered to possess sedat-
ing properties, and rosemary is believed to be arousing and has
been linked to memory at least as far back as the writings of Shake-
speare (Hamlet Act4, scene5). These facets are broadly reflected in
the effects on cognitive performance observed here.
The quality of memory factor was found to be impaired by lav-
ender when compared to rosemary, but not when compared to
controls. Consideration of the memory subfactors indicates that
secondary memory possessed the same odor-performance relation-
ship, although on this subfactor performance in the lavender condi-
tion was on a par with controls, indicating enhancement for the
rosemary condition rather than a decrement for lavender. For the
working memory subfactor, however, lavender was significantly im-
paired compared to both the rosemary and control conditions. A
clear dissociation of the aroma effects on these two memory sys-
tems is apparent here, with rosemary enhancing secondary memory
and lavender having no effect, in contrast to lavender which im-
paired working memory and rosemary which had no effect. A simi-
lar profile of results to those obtained here for rosemary has been
reported previously for the influence of oxygen administration on
cognition (Moss et al., 1998) and for the acute administration of
Ginseng (Kennedy et al., 2000). It is interesting to note that the
distinction between secondary and working memory appears to be
more than theoretical on the basis of the results reported here and
elsewhere. It may be the case that the two systems are served to
some degree by distinct neuropsychological and neurochemical path-
ways that are differentially available for enhancement, although some
natural interventions (most notably, chewing gum) appear capable
of impinging on both in a positive manner (Wilkinson et al., 2002).
With reference to the speed of memory factor, both aromas sig-
nificantly slowed performance as compared to controls. As this fac-
tor encompasses reaction times from both working memory and
secondary memory tasks, this may indicate a speed accuracy trade-
off in both the enhancement found for rosemary, and the impair-
ment found for lavender reported here. However, consideration of
the individual task outcome measures that make up these factors
indicates an interesting pattern. Reaction times were not signifi-
cantly slowed by rosemary compared to the other conditions on the
32 M. Moss et al.
word and picture recognition tasks, which constitute the secondary
memory tasks, which have a speed component associated with them.
However, both tasks did show improvements in accuracy, and, as
such, a clear speed accuracy trade-off can be discounted for rose-
mary. In contrast, lavender did not produce significantly faster per-
formance compared to controls on the spatial and numerical work-
ing tasks on which accuracy was impaired. Indeed, participants were
both slower and less accurate on these tasks. However, lavender did
produce a slowing of reaction times on the secondary memory tasks
that were not impaired in terms of accuracy. The reduction in speed
here possibly facilitates a level of accuracy that may otherwise have
been lost. The relationship between speed and accuracy may be
important in the effects of lavender then, but not rosemary.
The speed of attention factor displayed a significant impairment
for the lavender condition compared to controls, but not to rose-
mary. This may have, in part, been predicted on the basis of laven-
der’s putative sedating properties. Rosemary, however, would rea-
sonably have been predicted to enhance attentional speed as a
consequence of its arousing properties. Certainly the mood data in-
dicated that the participants in the rosemary condition felt more
alert than those in the lavender or control conditions. Performance
for the rosemary condition, however, was numerically slower than
the controls, and faster than the lavender group though neither com-
parison was significant. In spite of increased subjective alertness,
however, objective performance did not improve, which suggests
that the enhancements observed for memory may be independent of
subjective state.
Another possible explanation may be found in the inverted-U
relationship between arousal and performance described in the Yerkes-
Dodson law. Attentional tasks require the directing of psychological
resources to events in the environment, and arousal levels (as moni-
tored by changes in physiological parameters such as blood pres-
sure and heart rate) are low (or even reduced compared to resting)
for such tasks compared to tasks with a higher cognitive load (Lacey
& Lacey, 1970, 1974; Turner & Carroll, 1985a, 1985b). It may well
be the case that rosemary inhalation raises arousal levels to such an
extent that enhancement is not possible for attentional tasks (due to
overarousal). At the same time performance on the more cognitively
Essential Oils, Cognition, and Mood 33
demanding tasks relating to memory consolidation and retrieval is
enhanced (due to optimal arousal being attained for these tasks).
Performance on the accuracy of attention factor was effectively
equal across conditions, and consideration of the mean levels of
accuracy in the tasks that combine to create this factor suggests that
ceiling levels were being achieved. Accuracy levels of greater than
90% in the control condition indicates that there is very little room
for enhancement in the participant group employed here, and the
nature of the tasks is such that only serious cognitive deficits pro-
duce large impairments in accuracy of performance compared to
controls (Simpson et al., 1991). It is therefore perhaps not surpris-
ing that no effect of condition was observed on this factor.
Returning to the mood data, as well as the effect of rosemary on
levels of alertness, a significant effect was found for both lavender
and rosemary compared to controls for degree of contentedness.
Rosemary led to participants reporting higher levels of contented-
ness after completion of the test battery than before the start. In
addition, although lavender was associated with a small decrease in
levels of contentedness from pre- to post-testing, this change was
still significantly less than the decrease in contentedness observed
in the control condition. It would appear therefore that the aromas
employed here are capable of elevating mood, or at least maintain-
ing good mood during the completion of a challenging test battery
under laboratory conditions. These positive effects on mood are con-
sistent with those identified in the aromatherapy literature under
resting conditions (Buchbauer et al., 1991; van Toller & Dodd, 1988).
In contrast, no significant effect was revealed for the calmness mood
dimension, which may have been predicted to show an increase for
lavender based on its reported sedative properties. It may be that the
experimental situation experienced by the participants was such that
although feeling content, they did not find themselves able to relax
(i.e., increase calmness). This may also have been reflected in the
finding that lavender did not significantly decrease feelings of alert-
ness below those of controls. It may be possible that central or
conscious mechanisms were able to override the effects of the aroma
during testing at least for aspects of subjective mood, if not for the
objective measures of cognitive functioning as described above.
In considering how essential oils may influence mood and cogni-
34 M. Moss et al.
tion, such as that recorded here, a number of possibilities have been
proposed, but again little hard evidence exists. Jellinek (1997) out-
lined four mechanisms by which odors may exert effects. Two of
these can be rejected with regard to the current study. The “semantic
mechanism” describes contextual effects on memory and experi-
ence that were not investigated in this study. The “placebo mecha-
nism” describes the influence of expectancies on behavior and is
discounted here because the experiment explicitly set out not to
produce expectancies, and no participant indicated that he or she
had any during the testing procedure. The “hedonic valence mecha-
nism” asserts that the degree of pleasure/displeasure that is gained
from an experience defines the moods that emerge from it, and that
mood state affects cognitive and behavioral responses. Evidence sug-
gests that hedonic valence is affected by aromas (Baron & Thomley,
1994; Ehrlichman & Bastone, 1992) and that aromas may therefore
influence cognition via this route. Certainly, pleasant-smelling com-
mercially produced air-fresheners have been shown to improve mood
and task performance (Baron, 1990). In the current study, however,
differential cognitive effects were found for two essential oils, both
of which are considered to be pleasant smelling, and both of which
increased contentedness in participants compared to controls. As
such, a direct link to hedonic valence would appear too simple
to explain these results.
Finally, the “pharmacological mechanism” describes how con-
stituents of the essential oils may influence behavior through the
central nervous or endocrine systems. Volatile compounds may en-
ter the bloodstream by way of the nasal or lung mucosa, or may
diffuse directly into the olfactory nerve and pass up to the limbic
system in the brain—a region closely associated with arousal. Al-
though the level of active compounds that may be absorbed by
these routes is low compared to other modes of administration,
essential oils have been detected in the blood of rodents exposed
to the vapors of essential oils (Jirovitz et al., 1990, 1992; Kovar et
al., 1987). A pharmacological mechanism would imply substance-
specificity—a concept that would fit well with results described
here, with each aroma producing a unique pattern of influence on
the cognitive domains assessed. In addition, neuropharmacological
research has provided insights into the possible modes of influence
Essential Oils, Cognition, and Mood 35
of different plant-based substances that may be relevant here. Spe-
cifically, Wake and colleagues (Wake et al., 2000) found that vari-
eties of sage and melissa possessed nicotinic and muscarmnie acetyl-
choline activity in homogenate preparations of human cortical cell
membranes. The link between the cholinergic system and memory
is well established, and it may be that rosemary also possesses such
cholinergic activity—the results presented here suggest that it might.
This possibility remains to be investigated. Lavender has also been
demonstrated to act postsynaptically, and it is suggested that it mod-
ulates the activity of cyclic adenosine monophosphate (cAMP) (Lis-
Balchin & Hart, 1999). A reduction in cAMP activity is associated
with sedation, a causal relationship that has been established for the
effects of cannabis. It is possible that lavender produces sedative
effects via the same route albeit with less intensity.
In summary, the cognitive effects recorded here are clear, spe-
cific, and dependent upon ambient aroma. Furthermore, these ef-
fects only mirror to some degree the changes in subjective mood
state reported by the participants, and a simple change in levels of
arousal is not entirely satisfactory as an explanation of these find-
ings either. Recent work suggests that some of the essential oils
employed in aromatherapy possess pharmacological properties that
may be responsible for both the effects on mood and cognition
attributed to them. However, the information is currently limited
and further research is required if such properties and relationships
are to be identified clearly. At the same time, research in our lab
shall continue in an attempt to provide clear cognitive and mood
profiles for the effects of a wide range of essential oils.
REFERENCES
Ballard, C., O’Brien, J., Reichelt, K., & Perry, E. Aromatherapy as a safe and effective
treatment for the management of agitation in severe dementia: The results of a double
blind, placebo controlled trial. Journal of Clinical Psychiatry. (In press)
Baron, R. A. (1990). Environmentally-induced positive affect: Its impact on self efficacy,
task performance, negotiation and conflict. Journal of Applied Social Psychology, 20,
368–384.
Baron, R. A., & Thomley, J. (1994). A whiff of reality. Environment and Behaviour, 26,
766–784.
Bartram, T. (1995). Encyclopaedia of herbal medicines. Dorset, UK: Grace publishers.
Bond, A., & Lader, M. (1974). The use of analogue scales in rating subjective feelings.
British Journal of Medical Psychology, 47, 211–218.
36 M. Moss et al.
Buchbauer, G., Jirovetz, L., Jäger, W., Dietrich, H., Plank, C., & Karamat, E. (1991). Aroma-
therapy: Evidence for the sedative effect of the essential oil of lavender after inhala-
tion. Z Natuforsch, 46c, 1067–1072.
Degel, J., & Köster, E. P. (1999). Odours: Implicit memory and performance effects. Chemical
Senses, 24, 317–325.
Diego, M. A., Jones, N. A., Field, F., Hernandez-Reif, Schanberg, S., Kuhn, C. McAdam,
V., Galamaga, R., & Galamage M. (1998). Aromatherapy positively affects mood, EEG
patterns of alertness and math computations. International Journal of Neuroscience,
96, 217–224.
Ehrlichman, H., & Bastone, L. (1992). The use of odor in the study of emotion. In S. Van
Toller & G. Dodd (Eds.), Fragrance: The psychology and biology of perfume (pp. 143–
159). London: Elsevier.
Frey, P. W., & Colliver, I. A. (1973). Sensitivity and response measures for discrimination
learning. Learning Motivation, 4, 327–324.
Gilbert, A. N., Knasko, S. C., & Sabini, J. (1997). Sex differences in task performance
associated with attention to ambient odour. Archives of Environmental Health, 52(3),
195–199.
Ilmberger, J., Heuberger, E., Mahrhoferm C., Dessovic, H., Kowarik, D., & Buchbauer, G.
(2001). The influence of essential oils on human attention, 1: Alertness. Chemical Senses,
26, 239–245.
Jellinek, J. S. (1997). Psychodynamic odour effects and their mechanisms. Cosmetics and
Toiletries, 112, 61–71.
Jirovetz, J., Buchbauer, G., Jäger, W., Raverdino, V., & Nikiforov, A. (1990). Determina-
tion of lavender oil fragrance compounds in blood samples. Fresenius Journal of Ana-
lytical Chemistry, 338, 922–923.
Jirovetz, J., Buchbauer, G., Jäger, W., Woiieh, A., & Nikiforov, A. (1992). Analysis of
fragrance compounds in blood samples of mice by gas chromatography, mass spec-
trometry, GC/FTIR and GC/AES after inhalation of sandalwood oil. Biomedical Chro-
matography, 6, 133–134.
Kennedy, D. O., Scholey, A. B., & Wesnes, K. A. (2000). Dose dependent changes in
cognitive performance and mood following acute administration of ginseng to healthy
volunteers. Nutritional Neuroscience, 4, 295–310.
Kennedy, D. O., Scholey, A. B., & Wesnes, K. A. (2001). Differential, dose dependent
changes in cognitive performance following acute administration of a gingko biloba/
panax ginseng combination to healthy young volunteers. Nutritional Neuroscience, 4,
399–412.
Knasko, S. C., Gilbert, A. N., & Sabini, J. (1990). Emotional state, physical well being,
and performance in the presence of a feigned ambient odour. Journal of Applied So-
cial Psychology, 20(16), 1345–1357.
Kovar, K. A., Gropper, B., Friess, & Ammon, H. T. P. (1987). Blood levels of 1,8-cineole
and locomotor activity of mice after inhalation and oral administration of rosemary
oil. Planta Medica, 53, 315–319.
Kubota, M., Ikemoto, T., & Komaki, R. (1992). In H. Woidich & G. Buchbauer (Eds.),
Proceedings of the 12th international congress of flavours, fragrances and essential
oils (pp. 456–461). Austrian Association of Flavour and Fragrance.
Lacey, J. I., & Lacey, B. C. (1970). Some autonomic-central nervous system interrelation-
ships. In P. Black (Ed.), Physiological correlates of emotion (pp. 104–123). New York:
Academic Press.
Lacey, B. C., & Lacey, J. I. (1974). Studies of heartrate and other bodily processes in
sensorimotor behaviour. In P. A. Obrist, A. H. Black, J. Brener, & L. V. DiCara (Eds.),
Cardiovascular psychophysiology (pp. 67–85). Chicago: Aldine.
Lis-Balchin, M., & Hart, S. (1999). Studies on the mode of action of the essential oil of
lavender (Lavandula angustifolia P. Miller). Phytotherapy Research, 13(6), 540–542.
Long, T. S., & Schwartz, G. E. (1987b). EEG activity during relaxation and food imagery.
Psychophysiology, 24, 599.
Essential Oils, Cognition, and Mood 37
Ludvigson, H. W., & Rottman, R. (1989). Effects of ambient odours of lavender and cloves
on cognition, memory, affect and mood. Chemical Senses, 14(4), 525–536.
Moss, M. C., Scholey, A. B., & Wesnes, K. A. (1998) Oxygen administration selectively
enhances cognitive performance in healthy young adults: A placebo controlled double-
blind crossover study. Psychopharmacology, 148, 27–33.
Parasuraman, R., Warm, J. S., & Dember, W. N. (1992). Effects of olfactory stimulation
on skin conductance and event-related potentials during visual sustained attention. Progress
Report No. 6. Submitted to the Fragrance Research Fund Ltd.
Price, S. (1995). Aromatherapy for health professionals. Edinburgh: Churchill Livingstone.
Roberts, A., & Williams, J. M. G. (1992). The effect of olfactory stimulation on fluency
vividness of imagery and associated mood: A preliminary study. British Journal of
Medical Psychology, 65, 197–199.
Sanderson, H., & Ruddle, J. (1992). Aromatherapy and occupational therapy. British Jour-
nal of Occupational Therapy, 55, 310–314.
Scholey, A. B., Moss, M. C., Neave, N., & Wesnes, K. A. (1999). Cognitive performance
hyperoxia and heart rate following oxygen administration in healthy young adults. Physiology
and Behaviour, 67, 783–789.
Schwartz, G. E., Whitehorn, D., Hernon, J. C., & Jones, M. (1986b). Subjective and res-
piratory differences of fragrances: Interaction with hedonics. Psychphysiology, 23, 460.
Simpson, P. M., Surmon, D. J., Wesnes, K. A., & Wilcock, G. K. (1991). The cognitive
drug research computerized assessment system for dementia patients: A validation study.
International Journal of Geriatric Psychiatry, 6, 95–102.
Steiner, W. (1994). In P. Jellinek (Ed.), Die pschologischen grundlagen der parfumerie,
(4th
ed., pp. 195–213). Heidelberg: Hüthig Verlag.
Sugano, H. (1992). In S. van Toller & G. Dodd (Eds.), Fragrance: The psychology and
biology of perfume (pp. 221–228). London: Elsevier.
Torri, S., & Fukuda, H. (1985). The effect of odours on the contingent negative variation
(CNV). Proceedings of the 19th Japanese symposium on taste and smell.
Torii, S., & Fukuda, H., Kanemoto, H., Miyanchi, R., Hamauzu, Y., & Kawasaki, M. (1988).
Contingent negative variation and the psychological effects of odour. In S. van Toller
& G. Dodd (Eds.), Perfumery: The psychology and biology of fragrance. London: Chapman
and Hall.
Turner, J. R., & Carroll, D. (1985a). Heart rate and oxygen consumption during mental
arithmetic, a video game, and graded exercise: Further evidence of metabolically-ex-
aggerated cardiac adjustments. Psychphysiology, 22, 261–267
Turner, J. R., & Carroll, D. (1985b). The relationship between laboratory and real world
heartrate reactivity: An exploratory study. In J. F. Orlebeke, G. Mulder, & L. J. P. Van
Doornen (Eds.), Psychophysiology and cardiovascular control: Methods, models and
data (pp. 895–908). New York: Plenum.
Valnet, R. (1986). The practice of aromatherapy. Rochester, VT: Healing Arts Press.
van Tollen, S., & Dodd, G. H. (1988). In S. van Toller & G. H. Dodd (Eds.), Perfumery:
The psychology and biology of fragrances. Elsevier Science Publications Ltd., London
and New York: Chapman and Hall.
Wake, G., Court, J., Pickering, A., Lewis, R., Wilkins, R., & Perry, E. (2000). CNS acetyl-
choline receptor activity in European medicinal plants traditionally used to improve
failing memory. Journal of Ethnopharmacology, 69(2), 105–114.
Warm, J. S., & Dember, W. N. (1990). Effects of fragrances on vigilance performance and
stress. Perfumer and Flavorist, 15, 15–18.
Warm, J. S., Dember, W. N., & Parasuraman, R. (1991). Effects of olfactory stimulation
on performance and stress in a visual sustained attention task. Journal of Social Cos-
metic Chemistry, 42, 199–210.
Wesnes, K. A., Faleni, R. A., Hefting, N. R., Hoogsteen, G., Houben, J. J. G., Leonard, J.,
Petrini, O., & van Lier, J. J. (1997). The cognitive subjective and physical effects of
Ginkgo biloba/Panax ginseng combination in healthy volunteers with neuroasthenic
complaints. Psychopharmacology Bulletin, 33, 677–683.
38 M. Moss et al.
Wesnes, K. A., Wand, T. Ayre, G., & Pincock, C. (1999). Validity and utility of the cog-
nitive drug research (CDR) computerized assessment system: A review following fif-
teen years of usage. European Neuropsychopharmacology, 9(sup. 5), S368.
Wesnes, K. A., Ward, T., & McGinty, A. (2000). The memory enhancing effects of Ginkgo
biloba/Panax ginseng combination in healthy middle aged volunteers. Psychopharma-
cology, 152, 353–361.
Wilkinson, L., Scholey, A. B., & Wesnes, K. (2002). Chewing gum selectively improves
aspects of memory in healthy volunteers. Appetite, 38, 1–2.
Yerkes, R., & Dodson, J. (1908). The relation of strength of stimulus to rapidity of habit-
formation. Journal of Comparative Neurology and Psychology, 18, 459–482.
