How does fragrance influence our emotional state?

30 Nov

The Biology and Psychology of Essential Oils.

How does fragrance influence our emotional state? By Veronica Massa, 2007

…people could close their eyes to greatness, to horrors, to beauty, and their ears to melodies or deceiving words. But they could not escape scent. For scent was a brother to breath. Together with breath it entered human beings, who could not defend themselves against it, not if they wanted to live. And scent entered the very core, went directly to their hearts, and decided for good and all between affection and contempt, disgust and lust, love and hate. He who ruled scent ruled the heart of men.

Patrick Suskind, Parfume: The story of a murderer.

Scents evoke many images and sensations. Every major culture throughout history has used aromatics to create special moods. In Egypt scented oils and incense has been used from the earliest historical times. Pharaohs indulged in sweet ointments, scented substances was provided for use in the Hereafter, and the Moringa oil used as base oil for perfumes was distributed for the enjoyment of the population outside the palace. In Egypt, perfume wasn't like the perfume of today, perfume was holistic, much as aromatherapy today. It may be for its stronger scent and effect that the blu lotus has appear so frequently in Egiptian decorations.

The effect of the scent of the lotus flower was used to open the heart of divinity, same as that of ordinary mortals, intimately affected by the ‘divinity’ of its scent, which could be interpreted as sedative or hypnotic ‘causing to dilate the nostrils’. Documents show as Egiptians were already aware of the use of scents with the specific purpose of producing a psychic effect. At a time when man’s senses had not yet been pampered with products obtained through distillation, not to mention modern artificial preparations, sensitivity to natural scents must have been even more acute (Lise manniche 1999). For an Egyptian to indulge on the beautiful smell of a lotus flower had to be sufficient to provoke on him a considerable effect enough to achieve an alteration of his consciousness.

Nefertem, God of Perfume, Water Lily of the Sun… Nefertem was the god of both healing and beautification, perfumes and aromatherapy.. As a god of the water lily (lotus) (specifically, the blue water lily), he used its narcotic qualities for medicinal purposes as well as for perfumes and adornment. Votive offerings to Nefertem were primarily lotus and other flowers.

A considerable number of plant produce the effect of liberation of the mind, with the ability to cause sedation and exitement.

But how does that happen?

“Aristotle says that the fragrant breaths of perfumes, flowers and meadows are no less conducive to health than to pleasure, in that they spread softly with warmth and mildness through the brain which is by nature cold and congealed” (Griffiths 1970).

The olfactory system, which senses and processes odours, is one of the oldest and most vital parts of the brain. A primal part of our brain responds to smell and is activated from birth. We smell and react to different aromas before we learn to differentiate between colours, sounds or textures. Olfactory communication allows the newborn baby to identify and locate his mother. Smell triggers nursing instinct in animals like in humans, in the same way a mother can recognize her own baby by odour. It is also known that during pregnancy the sense of smell of a human is heightened by the hormonal change, bringing humans closer to their animal nature which in today’s civilized society has been suppressed neglecting that powerful instinct, still unconsciously used for self-preservation or specie preservation. Included is that protective mechanism that allows as to recognize a gone bad food or that primitive instinct related to sexual significance. Humans are greatly influenced by odour of others, which is reason of attraction or repulsion between two people, this is an unaware mechanism. Odour is an involuntary method of communication. We send signals through subliminal smells called pheromone which are airborne chemicals involuntarily expelled into the air that affect the physiology or behaviour of other members of the same species (Buckle 2003). Pheromones work in a subliminal way because humans are not aware of them, they are unique for everybody, Buckle describes them as a ‘smell print’.

Studies have been done to examine a wide range of effects that odors have on human psychological process such as mood, memory, and cognition. Results of some of these studies strongly support the notion that odors are powerful memory stimulants, which can spontaneously cue emotion and autobiographical data. They suggest that because of the uniqueness of the olfactory system with its direct contact to the limbic system and our emotions, stimuli are processed on an unconscious nonverbal level connecting past with present in a way very different from the other senses.

Considering this potent effect of odors on memory and emotions that research is illustrating more and more, it is easy to see why aromas can be such an important tool in the therapeutic process. Just talking about a scent can bring a whole host of memories into the interaction. Studies have shown that thinking about the scent can be as powerful as the scent itself (Betts, 1996). Mentioning certain scents or asking about odors during a session can bring about a deeper discussion of feelings and emotions, allowing the client to tune into the experience more intimately, to feel it more directly, and to connect with it on a fuller level.

Buckle mentions an example discussed by Espenshade (1999) that in this contest deserves to be reported. A selected mute child in the second grade does not responde in class to any questions since kindergarten. He had arrived at the school two years previously. The child was from Sardinian parents but was born in the united States. He behaved normally at home. Espenshade, a teacher , worked with the family and suggested six essential oils for the boy to choose from. The boy chose three: frankincense, bergamot, and Scotch pine. Each morning when he arrived at school he came to the teacher and selected one of the scents. Several drops were placed on a tissue he kept in his pocket. There was a gradual but definitive change. A few weeks into the study, the boy spoke for the first time in class. One particulat essential oil, Scotch pine, seemed to help him.When his father learned his soon had spoken in class for the first time, he asked which scent had worked. On hearing that it was Scoth pine, his comment was, “That is just how Sardinia smells!” The boy had never visited Sardinia.

In just one square inch of the brain, humans have the capacity to process about 10,000 different odours. The majority of aromas perceived involve a complex organization of hundreds of odour molecules, and through the simultaneous recognition of the individual odour molecules, a complex scent is recognized as a whole equal to the sum of its parts. 70 to 75% of what we perceive as taste actually comes from our sense of smell. More specifically, it is the odour molecules that enter the passage between the nose and mouth that gives us most of our taste sensation.

When inhaled, the odour molecule is absorbed in the nasal passage and binds to chemoreceptors in the olfactory epithelium, which are specific to certain odour molecules. This binding initiates a change in the permeability of the sensory neurons, which creates a slow electric potential that travels to the olfactory bulb. From the olfactory bulb, the transmitted signal is sent to the limbic system of the brain for further processing. Recognition of the odour occurs in the limbic system when the signal is interpreted through a comparison to past experiences with the odour and relation of the smell to the emitting substance. The limbic system, which receives information from the chemoreceptors about a particular odour, not only mediates mood and emotion, but also serves as a memory storage area. This common junction, where memories, emotions and odours meet, explains why smell is often an intense trigger for distinct memories and potent emotions. When perceiving a particular aroma that is associated with a past memory, the recognition of the odour in the olfactory process will simultaneously evoke the correlated memory. Determining the links between specific odours and a produced behaviour is a technique that scientists are still trying to perfect.

Learned memory is a reaction to a smell that has been learned through experience, for example trauma linked to an aroma. When that odour is smelled again, fear, or the emotion originally experienced, is triggered. This learned memory of smell can not be deleted from our brain. In the same way, smell can help people cope with a traumatic experience, for example it may be of use in treating panic attacks. Smell could produce psychologic effects similar to mood states, a pleasant smell produce a positive mood. Odours leave a lasting impression, long-term odour memory is even stronger than long-term visual memory., making of odours a powerful tool to recall memories even in cases of amnesia or comatose conditions. Several studies conducted on smell association memory have proven that smells can be an effective tool for memory association, and as long as the smell is perceived to be pleasant, it is not important which odour is used. Students exposed to pleasant smell while learning, remembered a considerably high percentage during examination if exposed to the same smell. In order to have a memory association, the same smell must be present at both learning and testing stage.

Research suggests that an individual odour molecule stimulates several types of receptors, each of which responds to a part of the molecule's structure. Brain mapping techniques have shown that the pattern of glomeruli activated by each odour forms a map or code that the brain may recognize as a unique scent.
Olfactory neurons, unlike most other types of neurons, are produced in constant supply with the regeneration of new cells approximately every 60 days to replace the dead olfactory neurons. Researchers are currently studying the possibility that insulin or other hormones may be responsible for the capability of olfactory cell growth, which is unique to the mammalian central nervous system By studying how olfactory neurons establish connections with other neurons in the adult brain, researchers hope to learn how nerve fibers connect in other brain regions. Unlike most neurons, olfactory neurons that die can be replaced by new neurons that serve the same function.
Learning how this process occurs may point to ways of making neurons regrow in other parts of the nervous system. Researchers are also studying how different receptors respond to different odours, which may lead to treatments for people in whom who age, disease or other factors have destroyed or damaged the sense of smell.
Similar receptors also may function in a special structure in the nose called the vomeronasal organ, which is thought to help detect special chemical signals called pheromones. These signals appear to regulate hormone release, mating, and social functions in animals, and possibly also in humans.
Olfactory information travels not only to the limbic system - primitive brain structures that govern emotions, behaviour, and memory storage - but also to the brain's cortex, or outer layer, where conscious thought occurs. In addition, it combines with taste information in the brain to create the sensation of flavour. Learning more about these links will help explain how odours affect our thoughts, emotions and behaviour.

Though the nose is commonly referred to as the organ of smell, this is only superficially true. Olfaction, which is the sense of smell, does not begin at the nose, although odour molecules do enter the two nasal passages of the nose. The neurons that sense these molecules lie deep within the nasal cavity, in a patch of cells called the olfactory epithelium. Each of the two nasal passages in humans has a 2.5 square centimetres patch containing about 50 million sensory receptor cells. These receptor cells send their axons into the olfactory bulb, a projection of the brain that lies over the nasal cavity in most primates, in the anterior region of the brain. The olfactory cilia of the sensory receptor cells (about 10-20 cilia for every olfactory neuron) are hair like projections. It is within these cilia that the specific odour molecules bind to their respective chemoreceptors. This binding causes a change in permeability of the sensory neuron, which creates a slow electric potential that travels to the olfactory bulb. From the olfactory bulb, the signal is transmitted to the limbic system in the brain, where memory is used to recognize the odour. The Limbic System contains the hypothalamus, the hippocampus, and the amygdale. These parts of the brain are responsible for our emotions and play key roles in the formation of memories. The limbic system, which receives information from the chemoreceptors about a particular odour, not only mediates mood and emotion, but also serves as a memory storage area. This common junction, where memories, emotions and odours meet, explains why smell is often an intense trigger for distinct memories and potent emotions. When perceiving a particular aroma that is associated with a past memory, the recognition of the odour in the olfactory process will simultaneously evoke the correlated memory.

Through this understanding of how odours are perceived, it is important to know why the limbic system allows us to behave differently when experiencing different odours. Knowing that the limbic system is an area where memory is utilized, we can partly understand the connection between past experiences and the same odour that we are smelling in the present. A question arises as to how the limbic system is able to remember past smells, while the fact is that the olfactory neurons are continually replaced after about every sixty days. The reason is, when the olfactory neurons die, a new set of neurons generates beneath them. These axons of neurons that express the same receptor always lead to the same destination. This is how memories survive in the limbic system.

Olfactory neurons, as mentioned before, are in contact with the limbic center of the brain. Because of the close connection to the limbic center, feelings and emotions can be regulated, as well as memory.

The use of scent can affect physical and psychological changes in humans. One study done in the United States found that inhalation of certain aromas appeared to be able to induce sustained weight loss over a six-month period. The research was published in the Journal of Neurological and Orthopedic Medicine and Surgery (1995). The study involved over 3,000 subjects and Alan R. Hirsch, M.D., neurologist and director of the Smell and Taste Treatment and Research Foundation in Chicago, Illinois conducted it. Dr. Hirsch wanted to see if smelling pleasant food aromas would help reduce appetite and food cravings in people, thereby helping them lose weight by reducing their food intake. Subjects were given plastic nasal inhalers scented with banana, green apple and peppermint. They sniffed the inhalers before, during and between meals. They recorded how often they sniffed. It was found that those who sniffed more frequently lost weight faster than those who did not. Dr. Hirsch explained that it worked because "Odours have a direct effect on the satiety centre in the brain, which is the area that tells your body when you've had enough to eat." Continual exposure to pleasant food aromas indicates to the brain that the body is satisfied and does not need to eat. It was shown in the study that there was successful weight loss.

Scientists attempt to learn about the details of emotional response generated from odors in the new science of aromachology, which is often mislabelled aromatherapy. The practice of aromatherapy has been documented since the days of Cleopatra, in which she allegedly used perfumes and aromatic oils to seduce Julius Caesar and Mark Antony. This practice involves the therapeutic use of herbal extracts as natural, "essential" oils to soothe the body, spirit and mind. Aromachology, on the other hand, is a newly developing science in which the effect of odours on behaviour is scientifically measured through carefully controlled experiments. Developed in 1982 by the Olfactory Research Fund, aromachology was designed "to scientifically study the interrelationship of psychology and fragrance technology" by analyzing the emotions produced when odours activate the olfactory pathways that lead to the limbic system of the brain. In this region, odours initiate the release of neurotransmitters, which can affect the brain and mental state of an individual invariety of ways. Serotonin produces a relaxing, soothing effect while endorphins inhibit pain and increase sexual arousal. Studies have shown that the use of certain aromas can benefit mood, behaviour and productivity by determining what neurotransmitters will be released. The field of aromachology is relatively new and thus continues to develop through continual advances in science and technology.

RESEARCH STUDIES:

Journal of Psychiatric Research
Volume 35, Issue 5, September-October 2001, Pages 271-277

Reduced olfactory performance in patients with major depression

Bettina M. Pause, a, Alejandra Mirandaa, Robert Göderb, Josef B. Aldenhoffb and Roman Ferstla
a Department of Psychology, Christian-Albrechts-University of Kiel, Olshausenstr. 62, 24098 Kiel, Germany
b Department of Psychiatry and Psychotherapy, Christian-Albrechts-University of Kiel, Germany
Received 8 December 2000; revised 2 June 2001; accepted 25 June 2001. Available online 2 October 2001.

Abstract

The aim of the present study is to investigate olfactory sensitivity and odor evaluations in a homogenous sample of unipolar depressive patients using pure olfactory odors. Twenty-four in-patients with major depressive disorder (MDD) were investigated during their acute depressive phase. Eighteen of them participated a second time after successful treatment. A group of healthy subjects, matched by age, sex, and smoking behavior, served as a control. Olfactory sensitivity, as measured by threshold tests, was strongly reduced in patients with severe depression. Additional correlative analyses revealed that the lowered sensitivity could partly be predicted by high depression scores. After successful medical treatment, these sensitivity differences were reduced and did not reach the significance level. The subjective odor evaluations (valence and intensity ratings) were not markedly changed in general. The results reveal that olfactory performance in MDD patients is reduced at an early perceptional level of stimulus processing. It is discussed whether this effect can be attributed to the close functional connection between the main olfactory bulb and the amygdala.

Impulse, undergraduate journal for Neuroscience
Olfaction, Emotion & the Amygdala: arousal-dependent modulation of long-term autobiographical memory and its association with olfaction

Mark Hughes

Centre for Neuroscience, The University of Edinburgh

2004

The sense of smell is set apart from other sensory modalities. Odours possess the capacity to trigger immediately strong emotional memories. Moreover, odorous stimuli provide a higher degree of memory retention than other sensory stimuli. Odour perception, even in its most elemental form - olfaction - already involves limbic structures. This early involvement is not paralleled in other sensory modalities. Bearing in mind the considerable connectivity with limbic structures, and the fact that an activation of the amygdala is capable of instantaneously evoking emotions and facilitating the encoding of memories, it is unsurprising that the sense of smell has its characteristic nature. The aim of this review is to analyse current understanding of higher olfactory information processing as it relates to the ability of odours to spontaneously cue highly vivid, affectively toned, and often very old autobiographical memories (episodes known anecdotally as Proust phenomena). Particular emphasis is placed on the diversity of functions attributed to the amygdala. Its role in modulating the encoding and retrieval of long-term memory is investigated with reference to lesion, electrophysiological, immediate early gene, and functional imaging studies in both rodents and humans. Additionally, the influence of hormonal modulation and the adrenergic system on emotional memory storage is outlined. I finish by proposing a schematic of some of the critical neural pathways that underlie the odour-associated encoding and retrieval of emotionally toned autobiographical memories.

Oxford Journals (Life Science, Chemical senses) Volume 24, Number 3; pp 327-335

Basic Emotions Evoked by Eugenol Odor Differ According to the Dental Experience. A Neurovegetative Analysis

O. Robin, O. Alaoui-Ismaïli1, A. Dittmar2 and E. Vernet-Maury1

Département de physiologie, Faculté d'Odontologie, Université Claude Bernard, LYON I, rue Guillaume Paradin, F-69372 Lyon Cedex 08, 1 Emotion et Vigilance, LPM, CNRS, INSA Lyon, bâtiment 401, 20 avenue Albert Einstein, F-69621 Villeurbanne Cedex, France 2 Microcapteurs microsystèmes biomédicaux, LPM, CNRS, INSA Lyon, bâtiment 401, 20 avenue Albert Einstein, F-69621 Villeurbanne Cedex, France

Abstract
Subjective individual experiences seem to indicate that odors may form strong connections with memories, especially those charged with emotional significance. In the dental field, this could be the case with the odorant eugenol, responsible for the typical clinging odor impregnating the dental office. The odor of eugenol could evoke memories of unpleasant dental experiences and, therefore, negative feelings such as anxiety and fear, since eugenates (cements containing eugenol) are used in potentially painful restorative dentistry. This hypothesis was tested by evaluating the emotional impact of the odor of eugenol through autonomic nervous system (ANS) analysis. The simultaneous variations of six ANS parameters (two electrodermal, two thermovascular and two cardiorespiratory), induced by the inhalation of this odorant, were recorded on volunteer subjects. Vanillin (a pleasant odorant) and propionic acid (an unpleasant one) served as controls. After the experiment, subjects were asked to rate the pleasantness versus unpleasantness of each odorant on an 11-point hedonic scale. The patterns of autonomic responses, obtained for each odorant and each subject, were transcribed into one of the six basic emotions defined by Ekman et al (happiness, surprise, sadness, fear, anger and disgust). Results were compared between two groups of subjects divided according to their dental experience (fearful and non-fearful dental care subjects) and showed significant differences only for eugenol. This odorant was rated as pleasant by non-fearful dental subjects but unpleasant by fearful dental subjects. The evoked autonomic responses were mainly associated with positive basic emotions (happiness and surprise) in non-fearful dental subjects and with negative basic emotions (fear, anger, disgust) in fearful dental subjects. These results suggest that eugenol can be responsible for different emotional states depending on the subjects' dental experience, which seems to confirm the potential role of odors as elicitors of emotional memories. This study also supports the possible influence of the ambient odor impregnating the dental office, strengthening a negative conditioning toward dental care in some anxious patients.

It can thus be suggested that eugenol odor could evoke memories of unpleasant dental experiences and contribute to dental anxiety and fear. This is supported by the results of Kirk-Smith et al. (1983), who demonstrated that if an unfamiliar odor is associated with a stressful situation, this odor may, at a later time, elicit concomitant mood and attitudinal changes. In the case of eugenol, its association with unpleasant dental care experiences could be explained by the fact that eugenates (cements containing eugenol) are often used in potentially painful restorative dentistry on vital teeth.

www.chemse.oxfordjournals.org

Proc. Natl. Acad. Sci. USA
Vol. 94, pp. 4119-4124, April 1997
Neurobiology

Emotion, olfaction, and the human amygdala: Amygdala activation during aversive olfactory stimulation

David H. Zald*,, and José V. Pardo*,

* Cognitive Neuroimaging Unit, Psychiatry Service, Veterans Affairs Medical Center, One Veterans Drive, Minneapolis, MN 55417; and Department of Psychology and Division of Neuroscience Research, Department of Psychiatry, University of Minnesota, Minneapolis, MN 55455

ABSTRACT

Electrophysiologic and lesion studies of animals increasingly implicate the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contributions of the amygdala and other limbic and paralimbic regions to emotional processing, we exposed healthy subjects to aversive olfactory stimuli while measuring regional cerebral blood flow (rCBF) with positron emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF within the left amygdala and the left OFC was highly intercorrelated, indicating a strong functional interaction between these brain regions. Furthermore, the activity within the left amygdala was associated significantly with subjective ratings of perceived aversiveness. These findings provide evidence that the human amygdala participates in the hedonic or emotional processing of olfactory stimuli.

INTRODUCTION

How the human brain processes emotions is unclear. Studies using electrophysiologic and lesion techniques suggest that the amygdala plays a crucial role in emotional processing in mammals. Amygdala lesions critically disrupt the development and expression of conditioned fear in rodents. Nonhuman primates with amygdala lesions demonstrate abnormal emotional responses to biologically significant stimuli (Kluver-Bucy syndrome), including marked reductions in the expression of fear and aggression. Single cell studies of the amygdala in nonhuman primates indicate that the activity of many amygdala cells depends on the hedonic significance of stimuli. These cells do not respond to sensory stimuli per se but to stimuli with unconditioned or conditioned aversive (punishing) qualities. Such research suggests that the amygdala may play an important role in emotional processing and psychopathology in humans. However, an understanding of the functions of the human amygdala has proven elusive.

Data regarding the role of the amygdala in humans remain scarce and are largely limited to case studies of patients with neurological conditions. The observation that electrical stimulation and seizures focused on the human amygdala frequently produce fear or other emotional responses provides strong evidence implicating the amygdala in emotional processing in humans. However, lesions of the amygdala in humans rarely produce the constellation of emotional abnormalities associated with lesions of the amygdala in nonhuman primates, except when amygdala damage occurs in conjunction with diffuse cerebral disease. Recently, several cases of selective amygdala lesions due to Urbach-Wiethe syndrome have been reported. Studies of these patients indicate that bilateral amygdala lesions cause impairments in storing or recalling emotional memories, selective impairments in the recognition of fearful (but not positive) facial expressions, and impairments in cross-modal associations of olfactory and visual stimuli.

The anatomy and behavioral features of olfactory processing suggest that hedonically valenced olfactory stimuli may act as useful probes for studying limbic regions. The perception of smell is dominated by a hedonic (pleasantness-unpleasantness) dimension, and exposure to odorants produces robust approach and withdrawal responses. For example, the smell of smoke can evoke potently either fear and withdrawal responses or happiness and approach responses, depending on the circumstances surrounding odor perception. Such phenomena reflect the inextricable anatomical connections between the mammalian limbic and olfactory systems. The primary olfactory cortex (POC) is continuous with the anterior portion of the amygdala and projects directly to the amygdala and posterior orbitofrontal cortex (OFC) as well as perirhinal, entorhinal, and insular cortices. Approximately 40% of the neurons in the rodent amygdala respond to olfactory stimulation. Despite the amygdala's diminishing role in olfaction during evolution, primates retain direct projections from the lateral olfactory tract to the anterior cortical nucleus of the amygdala, and the medial nucleus of the amygdala remains intimately connected with the POC. As such, olfaction is the only exteroceptive sensory modality possessing direct bidirectional projections between the amygdala and primary sensory cortex. This anatomy suggests a high level of functional connectivity between the olfactory and limbic systems. Not surprisingly, the medial amygdala has been observed to increase its firing during the inhalation of odorants as measured electrophysiologically in conscious monkeys and humans.

Based on evidence cited above, we hypothesized that odorants with strong hedonic qualities would activate the human amygdala and other limbic or paralimbic regions receiving olfactory input. To test this, we exposed healthy subjects to aversively valenced olfactory stimuli while regional cerebral blood flow (rCBF), a marker of neuronal activity, was measured with positron emission tomography (PET).

ABBREVIATIONS

OFC, orbitofrontal cortex; PET, positron emission tomography; POC, primary olfactory cortex; rCBF, regional cerebral blood flow; ROI, region of interest; UPSIT, University of Pennsylvania Smell Identification Test.

Annals of the New York Academy of Sciences

Volume 855 OLFACTION AND TASTE XII: AN INTERNATIONAL SYMPOSIUM Page 670-674, November 1998

To cite this article: RACHEL S. HERZ (1998)
Are Odors the Best Cues to Memory? A Cross-Modal Comparison of Associative Memory Stimulia
Annals of the New York Academy of Sciences 855 (1), 670–674.
doi:10.1111/j.1749-6632.1998.tb10643.x

Are Odors the Best Cues to Memory? A Cross-Modal Comparison of Associative Memory Stimulia

RACHEL S. HERZ, bTel: (215) 898-5022; fax: (215) 898-2084; email: herz@pobox.upenn.edu11Monell Chemical Senses Center, 3500 Market Street, Philadelphia, Pennsylvania 19104, USA1Monell Chemical Senses Center, 3500 Market Street, Philadelphia, Pennsylvania 19104, USA

ABSTRACT

To test the claim that odors are the 'best' cues to memory, several cross-modal experiments were conducted in which odors were compared with verbal, visual, tactile and musical stimuli as associated memory cues. Each experiment comprised two sessions (encoding and retrieval) separated by 48 hr. At the encoding session, a series of stimuli were incidentally associated to a set of emotionally arousing pictures. At the retrieval session, memory accu racy and emotionality were assessed. Across experiments, results revealed that odors were equivalent to other stimuli in their ability to elicit accurate recall, but that odor-evoked memories were always more emotional. Notably, emotional responses did not vary as a function of stimulus type at encoding. These data indicate that emotional saliency, rather than accuracy, is responsible for the impression that odors are superior reminders, and that retrieval processes (cf. encoding processes) are responsible for the distinctive emotionality of odor-evoked memories.