The influence of verbal labeling on the perception of odors: evidence for olfactory illusions?

Using the definition that an illusion is observed when a stimulus is invariant but context alters its perception, we examined whether verbal context could produce olfactory illusions. To test this effect, we chose five odors with minimally fixed sources and that could be interpreted with various hedonic connotations. The odors were violet leaf, patchouli, pine oil, menthol, and a 1:1 mixture of isovaleric and butyric acids. Subjects individually sniffed each odor at two different sessions separated by one week. At each session an odor was given a different verbal label (either positive or negative) and subjects rated the odors on several hedonic scales and provided perceptual and interpretative responses to them. Results showed that the perception of an odor could be significantly influenced by the label provided for it. We propose that the cases where verbal labels inverted odor perception are the first empirical demonstrations of olfactory illusions.

Verbal coding in olfactory versus nonolfactory cognition.

Two paired-associate memory experiments were conducted to investigate verbal coding in olfactory versus nonolfactory cognition. Experiment 1 examined the effects of switching/not switching odors and visual items to words between encoding and test sessions. Experiment 2 examined switching/not switching perceptual odors and verbal-imagine versions of odors with each other. Experiment 1 showed that memory was impaired for odors but not visual cues when they were switched to their verbal form at test. Experiment 2 revealed that memory was impaired for both odors and verbal-imagine cues when they were switched in format at test and that odor sensory imagery was not accessed by the instruction to imagine a smell. Together, these findings suggest that olfaction is distinguished from other sensory systems by the degree of verbal coding involved in associated cognitive processing.

Hemispheric lateralization in the processing of odor pleasantness versus odor names.

It is well established that for most people linguistic processing is primarily a left hemisphere activity, whereas recent evidence has shown that basic odor perception is more lateralized to the right hemisphere. Importantly, under certain conditions, emotional responding also shows right hemisphere laterality. Hedonic (pleasantness) assessments constitute basic level emotional responses. Given that olfaction is predominantly ipsilateral in function, it was hypothesized that odor pleasantness evaluations may be accentuated by right nostril perception and that odor naming would be superior with left nostril perception. To test this prediction we presented eight familiar neutral-mildly pleasant odors for subjects to sniff through the left and right nostrils. Subjects smelled each odor twice (once through each nostril) at two different sessions, separated by 1 week. At each session subjects provided pleasantness, arousal and naming responses to each odorant. Results revealed that odors were rated as more pleasant when sniffed through the right nostril and named more correctly when sniffed through the left. No effects for arousal were obtained. These findings are consistent with previously demonstrated neural laterality in the processing of olfaction, emotion and language, and suggest that a local and functional convergence may exist between olfaction and emotional processing.

Ambient odors associated to failure influence cognitive performance in children.

We investigated whether odors can become conditioned to emotionally salient experiences such that when later encountered they influence performance consistent with a previously associated event. To test this hypothesis, 5-year-olds were given the experience of failure/frustration on a cognitive maze in a room scented with fragrance and later given another cognitively challenging test in a different room scented with either the same odor, a different odor, or no odor. Results revealed that subjects who performed the test in the presence of the same odor as the maze task did significantly worse than subjects in any other group. Performance in the different odor and the no odor groups were equivalent. Facial expressions and verbal remarks made during the maze task indicated a predominant display of negative affect. These findings show that odors can become conditioned to experiential states and when later encountered have directional influences on behavior.

Caffeine effects on mood and memory.

The purpose of the present research was to assess whether a psychoactive dose of caffeine would have differential affects on the mood dimensions of arousal versus feelings of pleasantness and whether these mood alterations would influence memory either by (1) the experience of arousal at learning and/or (2) altered and congruent mood states at learning and recall. To address these questions, the administration of 5 mg/kg caffeine or placebo at learning and retrieval sessions was manipulated and subjects' mood was evaluated by several different self-report measures. Sixteen words were incidentally studied during the learning session and memory was evaluated by the number of words correctly recalled at the retrieval session two days later. Results revealed that caffeine reliably increased arousal, but did not affect any emotion dimensions related to feelings of pleasure. Subjects who received caffeine at learning and retrieval were also in equivalent mood states at both sessions. Moreover, caffeine did not produce any effects on memory; thus, neither hypothesis concerning the influence of arousal on memory was supported. These data show that caffeine is a useful method for manipulating arousal in the laboratory without influencing feelings of pleasantness or learning and memory performance.

Are odors the best cues to memory? A cross-modal comparison of associative memory stimuli.

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 accuracy 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.

The effects of cue distinctiveness on odor-based context-dependent memory.

The distinctiveness of an ambient odor was examined in relation to its success as a cue in context-dependent memory. Distinctiveness was examined in terms of both cue novelty and contextual appropriateness. Two experiments were conducted in which three different ambient odors that varied in familiarity and contextual appropriateness were manipulated at an incidental word learning encoding session and at a free recall retrieval session 48 h later. Experiment 1 revealed that when a novel ambient odor (osmanthus) was the available context cue, word recall was better than in any other condition. Further, among familiar odor cues, recall was better with a contextually inappropriate odor (peppermint) than with a contextually appropriate odor (clean fresh pine). Experiment 2 confirmed that superior word recall with osmanthus and peppermint depended on the odor cue's being available at both encoding and retrieval, and that the relation of an odor to the situational context is a key factor for predicting its effectiveness as a retrieval cue.

Emotion experienced during encoding enhances odor retrieval cue effectiveness.

Emotional potentiation may be a key variable in the formation of odor-associated memory. Two experiments were conducted in which a distinctive ambient odor was present or absent during encoding and retrieval sessions and subjects were in an anxious or neutral mood during encoding. Subjects' mood at retrieval was not manipulated. The laboratory mood induction used in Experiment 1 suggested that anxiety might increase the effectiveness of an odor retrieval cue. This trend was confirmed in Experiment 2 by capturing a naturally stressful situation. Subjects who had an ambient odor cue available and were in a preexam state during encoding recalled more words than subjects in any other group. These data are evidence that heightened emotion experienced during encoding with an ambient odor can enhance the effectiveness of an odor as a cue to memory.

Differential use of sensory information in sexual behavior as a function of gender.

Olfactory information is critical to mammalian sexual behavior. Based on parental investment theory the relative importance of olfaction compared with vision, touch, and hearing should be different for human males and females. In particular, because of its link to immunological profile and offspring viability, odor should be a more important determinant of sexual choice and arousal for females than for males. To test this hypothesis a questionnaire was developed and administered to 332 adults (166 males, 166 females). Subjects used a 1-7 scale to indicate how much they agreed with a series of statements concerning the importance of olfactory, visual, auditory, and tactile information for their sexual responsivity. The data reveal that males rated visual and olfactory information as being equally important for selecting a lover, while females considered olfactory information to be the single most important variable in mate choice. Additionally, when considering sexual activity, females singled out body odor from all other sensory experiences as most able to negatively affect desire, while males regarded odors as much more neutral stimuli for sexual arousal. The present results support recent findings in mice and humans concerning the relation of female preferences in body odor and major histocompatibility complex (MHC) compatibility and can be explained by an evolutionary analysis of sex differences in reproductive strategies. This work represents the first direct examination of the role of different forms of sensory information in human sexual behavior.

Odor memory: Review and analysis.

We critically review the cognitive literature on olfactory memory and identify the similarities and differences between odor memory and visual-verbal memory. We then analyze this literature using criteria from a multiple memory systems approach to determine whether olfactory memory can be considered to be a separate memory system. We conclude that olfactory memory has a variety of important distinguishing characteristics, but that more data are needed to confer this distinction. We suggest methods for the study of olfactory memory that should make a resolution on the separate memory system hypothesis possible while simultaneously advancing a synthetic understanding of olfaction and cognition.

The emotional distinctiveness of odor-evoked memories.

A modified paired-associate learning paradigm was used to test whether odors or verbal odor labels evoked more emotional memories. Subjects were presented with emotionally positive and negative paintings (to-be-remembered items) in association with positive and negative odors and odor labels. Painting recall and associated emotional experience were tested after 48 h. Odor-evoked memories were found to be more emotional than verbally cued memories on a variety of measures. Moreover, if the cue for recall (odor or label) was hedonically congruent with the painting to be remembered, memory for original emotional experiences was enhanced. The findings are discussed within a general cognitive framework and implications for using odors to dissociate the emotional and representational aspects of memory are addressed.

The hippocampal complex of food-storing birds.

Three families of North American passerines--chickadees, nuthatches and jays--store food. Previous research has shown that memory for the spatial locations of caches is the principal mechanism of cache recovery. It has also been previously shown that the hippocampal complex (hippocampus and area parahippocampalis) plays an important role in memory for cache sites. The present study determined the volume of the hippocampal complex and the telencephalon in 3 food-storing families and in 10 non-food-storing families and subfamilies of passerines. The hippocampal complex is larger in food-storing birds than in non-food-storing birds. This difference is greater than expected from allometric relations among the hippocampal complex, telencephalon and body weight. Food-storing families are not more closely related to each other than they are to non-food-storing families and subfamilies, and the greater size of the hippocampal complex in food-storing birds is therefore the result of evolutionary convergence. Natural selection has led to a larger hippocampal complex in birds that rely on memory to recover spatially dispersed food caches.

Comparison of the ability of (+)-amphetamine and caffeine to produce environment-specific conditioning.

Animals with a history of receiving psychomotor stimulants in a specific environment show enhanced activity when injected with saline and placed there. In the present study, a Pavlovian paradigm was used to compare the unconditioned and conditioned activity effects of (+)-amphetamine (0.1, 0.5, 1.0, and 5.0 mg/kg), caffeine (0.1, 1.0, 10.0, and 30.0 mg/kg), and a saline group (n's = 6-12). Rats experienced conditioning days with either drug or saline injected IP prior to a 60-min session in the activity monitor and the alternate saline or drug injected in the home cage following the session. On test days, all animals received saline in the activity monitors. Results revealed that amphetamine produced environment-specific conditioning in a dose-dependent manner; previous experience with 0.5, 1.0, and 5.0 but not 0.1 mg/kg in the activity monitor resulted in conditioned activity. A caffeine dose of 10.0 mg/kg produced stimulant effects on conditioning days and previous experience with the 1.0, 10.0, or 30.0 mg/kg dose in the activity monitor led to conditioned activity on test days. However, on test days the control groups as well as the 30.0 mg/kg experimental group showed significantly reduced activity as compared to the saline group. Thus, it appeared that caffeine produced hypoactivity 23 h after injection. Amphetamine produced conditioning in a dose-dependent manner, and the appearance of significant unconditioned activity during conditioning sessions was not necessary or sufficient to produce a conditioned effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Pimozide blocks establishment but not expression of cocaine-produced environment-specific conditioning.

Two experiments were conducted to examine the effects of pimozide on cocaine-produced conditioning to a specific environmental context. On 8 treatment days, 12 rats were injected with cocaine (10 mg/kg i.p.) and 12 with saline prior to placement for 60 min into a test chamber outfitted with infrared emitters and detectors. Following each treatment session the saline group received cocaine in their home-cages and the cocaine group received saline. Cocaine produced a significant increase in vertical activity on treatment days. On test days all rats received saline. Significantly greater vertical activity was observed in the group previously receiving cocaine in the test environment. All rats then received 8 more treatment sessions. On saline test days, pimozide (0.4 mg/kg i.p.) pretreatment failed to antagonize expression of the conditioned effect. In experiment 2, pimozide was given prior to treatment and no evidence of conditioning was seen on saline test days. Thus, pimozide blocked the establishment but not the expression of cocaine-produced environment-specific conditioning. These results suggest that during conditioning, the effects of cocaine on dopaminergic neurons may have produced a change that subsequently influenced behaviour even when dopaminergic systems were blocked.