Food neophobia and its relation with olfaction.

Food neophobia, that is the reluctance to try novel foods, is an attitude that dramatically affects human feeding behavior in many different aspects among which food preferences and food choices appear to be the most thoroughly considered. This attitude has an important evolutionary meaning since it protects the individual from ingesting potentially dangerous substances. On the other hand, it fosters an avoidance behavior that can extend even toward useful food elements. A strong link exists between food neophobia and both the variety in one person's diet and previous exposures to different foods. In this review, the more recent findings about food neophobia will be concisely described. Given the suggested connection between the exposure to different foods and food neophobia, this review will focus on the relation between this attitude and human chemosensory abilities. Olfaction, in particular, is a sensory modality that has a central role in flavor perception and in food preference acquisition. Therefore, the latest evidences about its relation with food neophobia will be discussed along with the applied and cognitive implications.

Food neophobia and its relation with olfactory ability in common odour identification.

Food neophobia is strictly connected with many different aspects of human feeding, ranging from food preferences to food choice, from active chemosensory exploration of the world (sniffing and tasting) to physiological responses associated with alertness. Therefore in this study, we tested the ability of 167 participants (54 women and 113 men, aged between 20 and 59 years old) to correctly identify 36 common odours, and we verified whether such ability could be related to their level of neophobia toward food and to demographic parameters (i.e., age, gender, and smoking habits). In the analyses, an advantage in odour identification abilities for non-neophobic people over more-neophobic participants was observed. As for participants' demographic information, a smaller reluctance to try new food in older than younger people was highlighted. The results of the present study suggest a connection between the attitude toward the exploration of the chemosensory environment and the ability to identify odours.

Olfactory discrimination: when vision matters?

Many previous studies have attempted to investigate the effect of visual cues on olfactory perception in humans. The majority of this research has only looked at the modulatory effect of color, which has typically been explained in terms of multisensory perceptual interactions. However, such crossmodal effects may equally well relate to interactions taking place at a higher level of information processing as well. In fact, it is well-known that semantic knowledge can have a substantial effect on people's olfactory perception. In the present study, we therefore investigated the influence of visual cues, consisting of color patches and/or shapes, on people's olfactory discrimination performance. Participants had to make speeded odor discrimination responses (lemon vs. strawberry) while viewing a red or yellow color patch, an outline drawing of a strawberry or lemon, or a combination of these color and shape cues. Even though participants were instructed to ignore the visual stimuli, our results demonstrate that the accuracy of their odor discrimination responses was influenced by visual distractors. This result shows that both color and shape information are taken into account during speeded olfactory discrimination, even when such information is completely task irrelevant, hinting at the automaticity of such higher level visual-olfactory crossmodal interactions.

Effects of olfactory stimuli on arm-reaching duration.

The aim of the present study was to investigate the effects of olfactory stimuli on visually guided reaching. In Experiment 1, participants reached toward and grasped either a small (almond/strawberry) or a large (apple/orange) visual target. Any 1 of 4 odors corresponding to the visual stimuli or odorless air was administered before movement initiation. Within the same block of trials, participants smelled 1) an odor associated with an object of a different size than the target, 2) an odor associated with an object of a size equal to that of the target, or 3) odorless air. Results indicated that reaching duration was longer for trials in which the odor "size" and the visual target did not match than when they matched. In Experiment 2, the same procedures were applied but the "no-odor" trials were administered in a separate block to the "odor" trials. Similar results as for Experiment 1 were found. However, in contrast to Experiment 1, the presence of an odor increased the level of alertness resulting in a shortening of reaching duration. We contend that olfactory stimuli have the capacity to elicit motor plans interfering with those programmed for a movement toward a visual stimulus.

Olfactory cues modulate facial attractiveness.

We report an experiment designed to investigate whether olfactory cues can influence people's judgments of facial attractiveness. Sixteen female participants judged the attractiveness of a series of male faces presented briefly on a computer monitor using a 9-point visual rating scale. While viewing each face, the participants were simultaneously presented with either clean air or else with 1 of 4 odorants (the odor was varied on a trial-by-trial basis) from a custom-built olfactometer. We included 2 pleasant odors (geranium and a male fragrance) and 2 unpleasant odors (rubber and body odor) as confirmed by pilot testing. The results showed that the participants rated the male faces as being significantly less attractive in the presence of an unpleasant odor than when the faces were presented together with a pleasant odor or with clean air (these conditions did not differ significantly). These results demonstrate the cross-modal influence that unpleasant odors can have on people's judgments of facial attractiveness. Interestingly, this pattern of results was unaffected by whether the odors were body relevant (the body odor and the male fragrance) or not (the rubber and geranium odors).

Neglect and extinction: within and between sensory modalities.

PURPOSE: The interest in human conscious awareness has increasingly propelled the study of neglect, the most striking occurrence of an acquired lack of conscious experience of space. Neglect syndromes commonly arise after unilateral brain damage that spares primary sensory areas nonetheless leading to a lack of conscious stimulus perception. Because of the central role of vision in our everyday life and motor behaviour, most research on neglect has been carried out in the visual domain. Here, we suggest that a comprehensive perspective on neglect should examine in parallel evidence from all sensory modalities. METHODS: We critically reviewed relevant literature on neglect within and between sensory modalities. RESULTS: A number of studies have investigated manifestations of neglect in the tactile and auditory modalities, as well as in the chemical senses, supporting the idea that neglect can arise in various sensory modalities, either separately or concurrently. Moreover, studies on extinction (i.e., failure to report the contralesional stimulus only when this is delivered together with a concurrent one in the ipsilesional side), a deficit to some extent related to neglect, showed strong interactions between sensory modality for the conscious perception of stimuli and representation of space. CONCLUSIONS: Examining neglect and extinction by taking into account evidence from all sensory modalities in parallel can provide deeper comprehension of the neglect syndrome mechanisms and possibly more effective multi-sensory based rehabilitation approaches.

Cross-modal interactions between olfaction and touch.

We report two experiments designed to investigate the nature of any cross-modal interactions between olfactory and tactile information processing. In Experiment 1, we assessed the influence of olfactory cues on the tactile perception of fabric softness using computer-controlled stimulus presentation. The results showed that participants rated fabric swatches as feeling significantly softer when presented with a lemon odor than when presented with an animal-like odor, demonstrating that olfactory cues can modulate tactile perception. In Experiment 2, we assessed whether this modulatory effect varied as a function of the particular odors being used and/or of the spatial coincidence between the olfactory and tactile stimuli. The results replicated those reported in Experiment 1 thus further supporting the claim that people's rating of tactile stimuli can be modulated by the presence of an odor. Taken together, the results of the two experiments reported here support the existence of a cross-modal interaction between olfaction and touch.