Odorless Control Research Articles

Nocturnal exposure to a preferred ambient scent does not affect dream emotionality or post-sleep core affect valence in young adults

Emotions experienced within sleep mentation (dreaming) affect mental functioning in waking life. There have been attempts at enhancing dream emotions using olfactory stimulation. Odors readily acquire affective value, but to profoundly influence emotional processing, they should bear personal significance for the perceiver rather than be generally pleasant. The main objective of the present sleep laboratory study was to examine whether prolonged nocturnal exposure to self-selected, preferred ambient room odor while asleep influences emotional aspects of sleep mentation and valence of post-sleep core affect. We asked twenty healthy participants (12 males, mean age 25 ± 4 years) to pick a commercially available scented room diffuser cartridge that most readily evoked positively valenced mental associations. In weekly intervals, the participants attended three sessions. After the adaptation visit, they were administered the odor exposure and odorless control condition in a balanced order. Participants were awakened five minutes into the first rapid eye movement (REM) stage that took place after 2:30 a.m. and, if they had been dreaming, they were asked to rate their mental sleep experience for pleasantness, emotional charge, and magnitude of positive and negative emotions and also to evaluate their post-sleep core affect valence. With rs < 0.20, no practically or statistically significant differences existed between exposure and control in any outcome measures. We conclude that in young, healthy participants, the practical value of olfactory stimulation with self-selected preferred scents for enhancement of dream emotions and post-sleep core affect valence is very limited.

Rub ‘n’ roll – Pigs, Sus scrofa domesticus, display rubbing and rolling behaviour when exposed to odours

Pigs are regarded as having a highly developed sense of smell, although scientific information on the topic is sparse. Here, we describe two behaviours unexpectedly observed in a study assessing pigs’ responses to odours and not previously reported in pigs. The study included 192 pigs of commercial breeds, tested in pairs with 12 different odours of non-social origin: 8 essential oils and 4 synthetic perfumes, plus an odourless control. Each odour was tested 24 times in triads of three odours. The results showed that, when exposed to odours, pigs display rubbing and rolling behaviour. Pigs displayed rubbing behaviour in 18 % of all odour exposures. Rolling behaviour was less frequent and displayed 7 times by five different pig pairs. Rubbing was always displayed following sniffing behaviour, and after a rubbing event, the pigs either performed sniffing behaviour (86.1 %), attempts at rolling (8.8 %) or a rolling event (5.1 %). Both males and females performed the rubbing behaviour (61 % female, 39 % male, Wilcoxon signed-rank test: W = 2199, P > 0.1), rolling behaviour (71 % female, 29 % male) and attempts at rolling (62 % female, 38 % male). Overall, essential oils (lavender, thyme, blood orange, aniseed, cedarwood, cinnamon bark, ginger, and pine) elicited more of the behaviours than the synthetic perfumes (vanilla, musk, apple, and jasmine) or the odourless control. All odours elicited rubbing whereas only four odours (blood orange, ginger, lavender, and pine) elicited rolling. Scent-rubbing/scent-rolling is a well-known behaviour in both wild (e.g., wolves and coyotes) and pet (e.g., cats and dogs) carnivores, although the function is not clear. This is the first report of rubbing and rolling as a response to an odour in pigs. The motivation for performing these behaviours is unknown but may include skin care, comfort behaviour or marking behaviour. Further studies allowing pigs physical access to rub and roll in different odours may elucidate the underlying motivation.

Effects of odors on posture

AbstractEvidence suggests that postural stability may benefit from olfactory exposure, but whether this effect is different for hyposmic and healthy subjects remains unknown and little attention has been paid to the hedonic valence of odors in this context. Forty‐five participants aged between 23 and 64 years were invited to this study, of whom 32 had normal olfactory function 13 exhibited olfactory deficits. Movement measurements were performed with the “Unterberger stepping test.” Participants walked in place with stretched arms for 8 periods of 30 s each, separated by intervals of approximately 15 s. During each of these 30‐s blocks one of the three odor conditions was presented to them: (a) pleasant odor, (b) unpleasant odor, and (c) odorless control. Both participants with normosmia and impaired olfaction moved to the left and right sides more when exposed to the unpleasant odor as compared to pleasant odor exposure or no odor. When smelling pleasant odors, participants presented shorter maximal anterior/posterior sway than during no odor exposure, but it was similar when smelling unpleasant odor. The study demonstrated strong effects of odors on postural stability with pleasant odors limiting and unpleasant enhancing postural sways.Practical ApplicationsOdors affect postural stability. Although we fail to demonstrate that postural stability measurements can be applied as a supporting method in smell dysfunction diagnosis, the current study opens prospects for further explorations of the relationship between olfactory and vestibular systems. These efforts may eventually lead to practical solutions supporting postural balance in patients suffering from conditions adversely affecting the vestibular system.

A Synthetic Blend of Fruit and Live Yeast Odours Shows Promise for Trapping Mated Female Queensland Fruit Fly, Bactrocera tryoni, in the Field.

Tephritid fruit flies are major horticultural pests of fruit and vegetable crops. Developing an odour lure that can attract mated female flies under field conditions has presented a major challenge to chemical ecologists around the globe. We have designed a new lure to attract female Queensland fruit fly, Bactrocera tryoni, based on the knowledge that this pest tephritid is attracted not only to odours from ripening fruits, but also to odours of symbiotic (gut-associated) yeasts on which the larvae feed. Initial field trials screened four volatile mixtures, each containing a base mix of three, short-chain "fruit ripening" esters and differing in the addition of long-chain "fruity" esters and / or alcohols produced by live yeasts. Results demonstrated that the lure formulated from short-chain esters and live yeast alcohols attracted the most female flies, with significantly higher catches than an odourless control trap, and a protein-baited trap. As electrophysiological studies exploring peripheral responses in tephritids to alcohols associated with fermentation have not been extensively investigated, we conducted this work on both the antennae and maxillary palps, and discovered that three yeast alcohols were detected by both sensory organs. Performance trials conducted in pome fruit and stone fruit orchards evaluated the six-component blend of short-chain ester and live yeast alcohol lure against a commercially available synthetic fruit-odour lure and a protein-based lure. In the apple orchard, the new lure caught significantly more female flies, and in particular mated females, compared to the commercially available lures. In the stone fruit orchard, while the new lure again caught the most mated female flies compared to the other lures, differences were not significant. The visual stimulus (trap design) used had a significant effect on capture, with a Ladd trap (red sphere on a yellow panel) being considerably more effective than the other traps. We discuss the implications of this study, including why the degree of effectiveness of the new lure might have differed among the test orchards (citrus, apple, stonefruit), and why yeast odours might increase attractiveness to "ripening fruit" volatile blends under field conditions.

Heterospecific eavesdropping on disturbance cues of a treefrog.

Alarm signals and cues are crucial to animal survival and vary greatly across species. Eavesdropping on heterospecific alarm signals and cues can provide eavesdroppers with information about potential threats. In addition to acoustic alarm signals, evidence has accumulated that chemical alarm cues and disturbance cues can also play a role in alerting conspecifics to potential danger in adult anurans (frogs and toads). However, there is very little known about whether disturbance cues are exploited by heterospecifics. In the present study, we conducted a binary choice experiment and a prey chemical discrimination experiment, respectively, to test the responses of a sympatric anuran species (red webbed treefrogs, Rhacophorus rhodopus) and a sympatric predator species (Chinese green tree vipers, Trimeresurus stejnegeri) to disturbance odors emitted by serrate-legged small treefrogs (Kurixalus odontotarsus). In the binary choice experiment, we found that the presence of disturbance odors did not significantly trigger the avoidance behavior of R. rhodopus. In the prey chemical discrimination experiment, compared with odors from undisturbed K. odontotarsus (control odors) and odorless control, T. stejnegeri showed a significantly higher tongue-flick rate in response to disturbance odors. This result implies that disturbance odor cues of K. odontotarsus can be exploited by eavesdropping predators to detect prey. Our study provides partial evidence for heterospecific eavesdropping on disturbance cues and has an important implication for understanding heterospecific eavesdropping on chemical cues of adult anurans.

Stress amelioration and anti-inflammatory potential of Shiikuwasha (Citrus depressa Hayata) essential oil, limonene, and γ-terpinene

Shiikuwasha (Citrus depressa Hayata) essential oil (SEO) extracted from Shiikuwasha fruit pulp contains two major volatile components, limonene and γ-terpinene (56.56–57.31 and 24.41–24.98%, respectively). In this study, we showed that the aroma streams of SEO, limonene, and γ-terpinene exhibited significant physiological stress amelioration effects in nine healthy female panelists tested in a 30-min visual display task. While SEO administration significantly reduced work errors by 15 min compared to the odorless control condition, the limonene stream reduced work errors only at the first and fourth 5-min intervals, and the γ-terpinene effect lasted only for the initial 5-min. However, γ-terpinene inhalation reduced stress by significantly increasing post-work electrocardiogram R-R interval variability and lowering electroencephalogram beta wave powers at the midline occipital Oz position. Additionally, SEO, limonene, and γ-terpinene displayed anti-inflammatory activity in vitro by suppressing the pro-inflammatory markers NO and IL-1β in BV-2 microglial cells in a dose-dependent manner.

Efficacy of Inhaled Essential Oil Use on Selected Symptoms Affecting Quality of Life in Patients With Cancer Receiving Infusion Therapies.

To evaluate the effects of inhaled ginger, German chamomile, and bergamot essential oil (EO) versus an odorless control oil on appetite, anxiety, fatigue, and nausea in individuals with cancer receiving IV therapy. 248 adults with gastrointestinal, neuroendocrine, or skin cancer receiving IV therapy from an academic cancer center. Participants were randomized to EO or control oil groups. Participants rated their symptoms during a seven-day period using a Likert-type scale ranging from 0 (no symptoms) to 10 (worst symptoms ever). Symptom burden was low. More men than women completed the study. The majority of participants had gastrointestinal cancer, followed by skin and neuroendocrine cancer. Ginger EO produced statistically significant results for anxiety and fatigue. Most participants were men and had gastrointestinal cancer. The high number of zero scores for symptoms may indicate the success of current symptom management regimens. Improvements in anxiety and fatigue using ginger EO warrant further study for validation.

Odour detection in children and young people with profound intellectual and multiple disabilities

BackgroundOlfaction provides information on very important dimensions of the environment; however the olfactory abilities of children and young people with profound intellectual and multiple disabilities (PIMD) remain largely unknown. This within‐subjects study explores olfactory detection abilities in children with PIMD.MethodTwenty‐two children and young people with PIMD (7–18 years) were presented with 18 medium intensity odours and an odourless control stimulus. Odorants were presented one by one in a randomised order. The neutral stimulus was presented prior to each odorant. Participants' responses were measured using 21 behavioural indicators.ResultsResults show that participants make a clear distinction between odorous and neutral conditions, between food and non‐food, and between pleasant and unpleasant odours. The detection abilities are manifested by several behaviours, in particular by the duration of the head alignment on the odorant.ConclusionsThis study shows that participants detect the stimuli and act differently depending on the category.

Olfaction-Related Factors Affecting Chemosensory Dream Content in a Sleep Laboratory.

Mental activity in sleep often involves visual and auditory content. Chemosensory (olfactory and gustatory) experiences are less common and underexplored. The aim of the study was to identify olfaction-related factors that may affect the occurrence of chemosensory dream content. Specifically, we investigated the effects of all-night exposure to an ambient odour, participants’ appraisal of their current olfactory environment, their general propensity to notice odours and act on them (i.e., odour awareness), and their olfactory acuity. Sixty pre-screened healthy young adults underwent olfactory assessment, completed a measure of odour awareness, and spent three nights in weekly intervals in a sleep laboratory. The purpose of the first visit was to adapt to the experimental setting. On the second visit, half of them were exposed to the smell of vanillin or thioglycolic acid and the other half to an odourless control condition. On the third visit, they received control or stimulation in a balanced order. On each visit, data were collected twice: once from the first rapid eye movement (REM) stage that occurred after 3 a.m., and then shortly before getting up, usually from a non-REM stage. Participants were asked to report the presence of sensory dream content and to assess their current olfactory environment. Neither exposure, nor participants’ assessments of the ambient odour, or olfactory acuity affected reports of chemosensory dream content but they were more frequent in individuals with greater odour awareness. This finding may have implications for treatment when such experiences become unwanted or bothersome.

Smells in Sustainable Environments: The Scented Silk Road to Spending.

Humanity's demand for ecological resources and services exceeds what earth can regenerate in that year, creating an urgent need for more sustainable behavior. Here, the focus is on a particular factor that so far has been overlooked in facilitating sustainable behavior, namely smell. The two-fold aim of this study was (i) to investigate whether ambient scent could enhance customers' subjective experience and spending behavior in a sustainable environment, and (ii) to elucidate the affective and cognitive pathways from scent to spending. To test this, a double-blind field experiment was designed where customers of a second-hand clothing store (N = 57) could face one of three conditions: fresh linen scent (pleasant and semantically priming “clean clothing” increasing the products' value), vanilla sandalwood scent (pleasant control odor), or regular store odor (odorless control). Buttressed by prior research, the fresh linen scent was expected to cause the strongest increase in spending behavior due to its positive semantic association with the product (i.e., clean clothing). The results indeed showed that fresh linen scent almost doubled consumer spending vs. the odorless control and the pleasant control odor. Other factors potentially affecting consumer behavior (e.g., weekday, weather, odor awareness) were uncorrelated. Whereas a conceptually-driven mediation analysis showed that only fresh linen scent increased mood and evaluations of the store, staff, and products, these variables did not mediate the relation between scent and spending. An explorative structural equation model suggested cognitive priming to be mainly responsible for increasing consumers' spending in the fresh linen condition by enhancing the general store evaluation. Further support is needed to corroborate the indirect findings that specific scents can follow a “cold” semantic road and a “hot” affective road to spending. At minimum, consumers are no “zombies” that empty their pockets in the presence of whatever odor; the smell needs to have a meaningful link to the (sustainable) context at hand to influence consumer behavior.

Do Food Odors Differently Influence Cerebral Activity Depending on Weight Status? An Electroencephalography Study of Implicit Olfactory Priming Effects on the Processing of Food Pictures

Attentional automatic processes and cerebral activity may differ between individuals with different weight statuses in the presence of food stimuli (e.g. odors, pictures). In the present study, we used an implicit olfactory priming paradigm to test the influence of non-attentively perceived food odors on the cerebral activity underlying the processing of food pictures, in normal-weight, overweight, and obese adults. A pear odor and a pound cake odor were used as primes, respectively priming sweet low-energy-density foods and high-energy-density foods. Event-related potentials were recorded while the participants passively watched pictures of sweet low and high-energy-density foods, under the two priming conditions plus an odorless control condition. The amplitude and latency of several peaks were measured (P100, N100, P200, N400). As a major result, we found that weight status influences the cerebral activity underlying the processing of food cues outside of consciousness, as early as the first detectable P100 peak.

Effects of all-night exposure to ambient odour on dreams and affective state upon waking

Previous laboratory research has shown that exposure to odours of contrasting pleasantness during sleep differentially affects the emotional tone of dreams. In the present study, we sought to investigate how a generally pleasant (vanillin) and unpleasant (thioglycolic acid [TGA]) smell influenced various dream characteristics, dream emotions, and post-sleep core affect during all-night exposure, controlling for appraisal of the olfactory environment during the assessments and sleep stage from which the participants woke up. We expected that exposure to vanillin would result in more pleasant dreams, more positive and less negative dream emotions, and a more positive post-sleep core affect compared to the control condition, whereas exposure to TGA would have the opposite effect. Sixty healthy volunteers (36 males, mean age 24 ± 4 years) were invited to visit the sleep laboratory three times in weekly intervals. The first visit served to adapt the participants to the laboratory environment. On the second visit, half the participants were exposed to an odour (vanillin or TGA, 1:1) and the other half to the odourless control condition. On the third visit, they received control or exposure in a balanced order. On each visit, the participants woke up twice, first from the rapid eye movement (REM) sleep stage and then in the morning, usually from a non-REM sleep stage. Repeated measures were taken upon each awakening. Dream pleasantness, emotional charge of the dream, positive and negative emotions experienced in the dream, and four dimensions of post-sleep core affect (valence, activation, pleasant activation – unpleasant deactivation, and unpleasant activation – pleasant deactivation) were assessed. We found a small effect of condition (exposure vs. control) in interaction with appraisal of the ambient olfactory environment on dream pleasantness. Specifically, false alarms (i.e., perceiving odour in the absence of the target stimulus) were associated with lower dream pleasantness than correct rejections. Although exposure had a statistically significant positive influence on post-sleep core affect (namely, valence, activation, and pleasant activation – unpleasant deactivation), the size of the effect was small and lacked practical significance. The hypothesised differential effects of vanillin and TGA were only modelled for dream ratings because they decreased the fit of the other models. Neither dream pleasantness nor emotionality differed according to the odour used for stimulation. The results of the present study suggest that all-night exposure to odours is unlikely to produce practically significant positive effects on dreams and post-sleep core affect.

Odours of non‐predatory species help prey moderate their risk assessment

Abstract Prey use contemporary information to update their risk estimation, and accordingly, optimize their anti‐predator reactions. Conceptualization of this process is largely focused on information that reflects predator activity. We aimed to complement this unilateral view by testing whether prey also use cues of non‐predatory species to update their risk perception. We focused our investigation on the desert isopod Hemilepistus reaumuri that reacts defensively to excavated soil mounds even in the absence of direct predator cues. We located in the field 19 isopod burrows and surrounded each with six soil mounds. One mound remained odourless and the other five were supplemented by odours of a major isopod predator, the golden scorpion, and four sympatric species that do not prey on isopods but excavate soil. Isopods augmented their defensive responses towards mounds supplemented by scorpion odours and lessened their anti‐predator reactions towards mounds with odours of herbivore rodents. Isopods’ responses to the odours of the two insectivorous species that do not eat isopods were similar to the reaction towards the odourless control mounds. Our results suggest that prey use non‐predatory species cues to moderate their risk estimation. Therefore, we need to consider this potentially important source of information in studies of predator–prey interactions. Our findings also indicate that odours or vocalization of non‐predatory species may not be adequate as control treatments to predator cues. A free Plain Language Summary can be found within the Supporting Information of this article.

The Asian grass lizard (Takydromus sexlineatus) does not respond to the scent of a native mammalian predator

AbstractLacertid lizards use chemical cues emitted by saurophagous snakes to evade predation. Whether these lizards can detect and respond to the chemical cues of predatory mammals has not been studied. As many mammals carry distinct body odours and/or use chemical cues for intraspecific communication, lizards can be expected to use these chemicals as early warning cues. To test this idea, we observed the behaviour of Asian grass lizards (Takydromus sexlineatus) that had been transferred to an unfamiliar test arena containing one of four scent treatments. No particular scent was applied to the arena in the control situation. Diluted aftershave served as a pungency control. In the snake treatment, scent of the Oriental whip snake (Ahaetulla prasina) was applied. We included this treatment to learn how Asian grass lizards react to predator chemical cues. Finally, in the mongoose treatment, the lizards were confronted with scent cues of several small Indian mongooses (Herpestes auropunctatus). Snake scent elicited foot shakes, startles and tail vibrations. These are behaviours that in lacertid lizards are associated with stressful situations such as predatory encounters. Surprisingly, lizards confronted with mongoose scent exhibited none of these stress‐indicating behaviours. In fact, their behaviour did not differ from that of lizards subjected to an odourless control treatment. These results raise concern. Mongooses are rapidly invading ecosystems worldwide. If lizards that have co‐evolved with mongooses are unable to detect these predators’ presence through chemical cues, it seems highly unlikely that evolutionary naïve lizards will develop this ability rapidly.

Sight or smell: which senses do scavenging raptors use to find food?

Raptors are usually considered to be mainly visually dependent, and the use of other sensory modalities has rarely been studied in these birds. Here, we investigated experimentally which senses (vision and/or olfaction) Turkey vultures (Cathartes aura) and Southern caracaras (Caracara plancus) use to find hidden food. First, two identical stainless-steel perforated balls, one containing a putrefied piece of meat and the other an odorless control, were presented to birds in binary choice experiments. Both species interacted more with the smelling ball than with the control, suggesting that they were attracted by the odor of the hidden meat. In a second experiment, individuals were accustomed to eat in one specifically colored ball (blue or green). In the test phase, the meat was hidden in the opposite color with respect to the one each bird had become accustomed to. Vultures still interacted more with the smelly ball disregarding the color, while caracaras interacted equally with the two balls. The prevalence of olfaction in Turkey vultures may partly explain why they are the first raptors to find carcasses in tropical forests. In contrast, caracaras forage on the ground opportunistically, a strategy where both olfaction and sight may be involved. Our experiments suggest that both species are able to use olfactory cues for foraging. However, olfaction could be the predominant sense in Turkey vultures while olfaction and sight could play an equivalent role in Southern caracaras.

Wild great and blue tits do not avoid chemical cues of predators when selecting cavities for roosting.

Small birds use cavities for roosting to decrease the thermoregulatory costs during the winter nights. The ability of birds to detect and escape from an approaching predator is impaired during roosting and thus the selection of such cavities should take into account the risk that a predator will find the cavity. Previous evidence suggested that birds in captivity are able to detect predator scent and avoid roosting in nest-boxes containing such predator chemical cues. Here, we tested whether birds also show this avoidance response under natural conditions. We performed three studies in three populations of blue and great tits. We added predator scent, a pungency scent or an odourless control to nest-boxes and compared the use of these nest-boxes for roosting. We found no differences between the scent treatments in the use of nest-boxes. Therefore, chemical cues indicating the potential presence of a predator are not enough for birds to avoid roosting in nest-boxes under natural conditions.

Antipredatory behaviour of a mountain lizard towards the chemical cues of its predatory snakes

Abstract The ability to early detect a potential predator is essential for survival. The potential of Iberolacerta cyreni lizards to discriminate between chemical cues of their two predatory snakes Coronella austriaca (a non-venomous active-hunter saurophagous specialist) and Vipera latastei (a venomous sit-and-wait generalist) was evaluated herein. A third snake species, Natrix maura, which does not prey on lizards, was used as a pungent control. Thus, the behaviour of I. cyreni was studied regarding four treatments: (1) C. austriaca scent, (2) V. latastei scent, (3) N. maura scent and (4) odourless control. Lizards showed antipredator behaviour (such as slow-motion and tail waving) to C. austriaca and V. latastei chemicals. The antipredatory response was similar for both predators. This ability to react with an intensive behavioural pattern to the chemical cues of their predatory snakes may prevent lizards from being detected, and, if detected, dissuade the predator from beginning a pursuit.

Development of test for determining olfactory investigation of complex odours in cattle

The sense of smell is likely to influence the behaviour of domestic and captive animals in a wide range of management and housing situations. In domestic cattle, there may be unexploited potential for using odours and olfaction in the management; however, published studies on bovine olfactory capacity are scarce. By applying an olfactory Habituation/Dishabituation test developed for rodents, this study aimed to assess olfactory ability in cattle. Twenty-three cows (n=10) and heifers (n=13) were tested with three different odours (orange juice, liquid coffee and tap water as an odourless control) presented in a test bucket. The test was conducted on individual animals in their home pen and consisted of each odour being presented twice in a row for 2min each with an inter-trial pause of 2min. Following another 2-min pause without odour the animal was presented with a new odour, with order of odour presentation balanced among animals. Duration of sniffing (muzzle in proximity or contact with) the test bucket as well as the occurrence of licking or biting the test bucket were recorded by direct observation. All animals sniffed an odour (i.e. the test bucket) less when presented for the second time (habituation; all 1st vs. 2nd presentations: P<0.001). Sniffing duration increased at the subsequent presentation of a new odour (dishabituation; all 2nd vs. 1st presentations: P<0.001). All animals sniffed coffee and orange longer than water (water vs. coffee: P<0.001 and water vs. orange: P<0.001), but they also sniffed coffee longer than orange (P=0.021). Licking or biting behaviour occurred only when presented with coffee or orange (13 out of 23 animals for both samples). The test showed that cows and heifers were able to distinguish between different complex odours (coffee and orange juice), and that the animals showed increased interest for one of the odours (coffee). This is the first example of a Habituation/Dishabituation test being adapted for and applied to cattle. The test may require further development, but represents the first steps towards exploring the possibility of using odours when adapting or enriching the environment in which we keep cattle.

Rapid acquisition of antipredatory responses to new predators by an insular lizard

Alien predators may impose a great threat to naive prey. Ibiza wall lizards (Podarcis pityusensis) live in Ibiza, a snake-free island until 2003. We studied the lizards’ discrimination of scents of two invader snakes: one that depredates lizards, the horseshoe whip snake (Hemorrhois hippocrepis), and another that does not, the ladder snake (Rhinechis scalaris). We compared two populations of Ibiza wall lizards: one from the main island of Ibiza, which coexists with both snakes, and another from the nearby snake-free islet of Sal Rossa. Lizards from Ibiza recognized the scent of the horseshoe whip snake and responded with clear antipredatory behaviours. However, they reacted to the scent of the ladder snake similarly to that of the controls (odourless control and pungent scent). Lizards from Sal Rossa did not respond to any of the snakes or the controls. Our results show that lizards can rapidly acquire the ability to react to a novel predator. As only about ten generations of lizards have coexisted with snakes, the most plausible explanation to our results is that lizards have learned to associate the scent of the predatory snake with a threat. This is the first study reporting the rapid acquisition of lizards’ antipredatory responses to the chemical cues of novel predators. However, more research is needed in order to identify the mechanisms implicated in the response. How naive prey acquire antipredator behaviour is both important for basic scientific research and useful for the conservation of native species subjected to biological invasions. The island of Ibiza (Spain) has been free from snakes until their introduction by humans in 2003. We compared the reaction of lizards from Ibiza (where presently three species of snakes cohabitate) and lizards from Sal Rossa (a nearby snake-free islet) to the scent of two snakes (one that feeds on lizards and other that does not). The results were clear: lizards from Ibiza react to the scent of the predatory snake with antipredatory behaviours, while ignoring the scent of the non-predatory snake. Lizards from the snake-free island of Sal Rossa did not react to any of the snakes. Our study shows that lizards can rapidly acquire the ability to react to a completely new type of predator, most likely by learning.

Influence of room fragrance on attention, anxiety and mood

AbstractWith a special focus on the potential benefits of widely used room scents, the aim of the present blinded study was to investigate attention, anxiety and mood in a large group of healthy people during exposure to various pleasant odours compared with the same situation in a non‐odourous environment. A psychological test battery (d2 test of attention, State‐Trait‐Anxiety‐Inventory, Beck Depression Inventory and Multidimensional Mood State Questionnaire) was applied to 200 normosmic subjects, placed in rooms with four different room fragrance conditions (rose odour; grapefruit odour; a combination of orange, lime and lemon odour; and a odourless control). After exposure, subjects were asked to rate occurrence and severity of heart problems (tachycardia/palpitations), headaches or breathing problems. Results revealed no significant effects of room fragrance on attention, anxiety and mood. Exposure to odours seemed to affect men and women differentially with men presenting unfavourable results in rose‐fragranced rooms whereas they seemed positively affected by the smell of grapefruit. However, these effects could only be observed when no corrections for multiple comparisons were applied. Exposure to the fragrances was not associated with a higher incidence of physical symptoms. These results suggest that the grapefruit odour may be a more suitable room fragrance for mixed‐gender groups than rose odour to reduce anxiety and to improve attention and mood. Copyright © 2016 John Wiley &amp; Sons, Ltd.