Abstract: 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.
Abstract: 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.
Abstract: We investigated whether the crossmodal associations between olfaction and touch reported previously in studies involving subjective report measures could also be demonstrated using an indirect measure of crossmodal association. To this end, we used a modified version of the Implicit Association Test. The participants had to make speeded discrimination responses to a series of unimodally presented olfactory (lemon vs. animal odour) or tactile stimuli (soft vs. rough fabric) using two response keys. In compatible blocks of trials, the olfactory and tactile stimuli that were mapped onto the same response key were considered to share a stronger association (e.g., the lemon odour and the soft fabric) than those that were combined onto the same response key in the incompatible blocks of trials (e.g., the animal odour and the soft fabric). The results showed that the participants responded significantly more rapidly in the compatible response mapping blocks than in the incompatible blocks, thus confirming the existence of associations between the stimuli that were considered to be compatible. These results provide the first empirical evidence that olfactory-tactile crossmodal associations are stable enough to influence performance even when not directly relevant to a participant's task.
Abstract: 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).
Abstract: In the present study, we investigated the nature of any cross-modal associations between colors and odors. In Experiment 1, we show that participants consistently match certain odors to specific colors when asked to explicitly select from among different colors the one that best matched a given odor. In Experiment 2, we investigated the robustness of these cross-modal associations using a cross-modal variant of the implicit association test (IAT). Participants made speeded discrimination responses to a random sequence of odors (strawberry vs. spearmint) and color patches (pink vs. turquoise). On the basis of the results of Experiment 1, the assignment of these targets onto the two response keys was manipulated in order to generate compatible (e.g., responding to the pink color and to the strawberry odor with the same response key) and incompatible (e.g., responding to the pink color and to the spearmint odor with the same response key) blocks of trials. The results showed that participants responded more rapidly and accurately to odor-color pairings having a stronger association than to those having a weaker (or no) association. These results suggest that odor-color associations can be both systematic and robust. The paradigm developed here provides a novel cross-modal extension of the IAT to probe the nature of color-odor associations.
Abstract: 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.
Abstract: 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.
Abstract: BACKGROUND: The space closely surrounding the body, near peripersonal space, is represented through multisensory coding, as witnessed by the spatial distribution of visual-tactile extinction in brain-damaged patients. Typically, tactile stimuli delivered on the contralesional hand are more severely extinguished by visual stimuli presented near to than far from the ipsilesional hand. OBJECTIVE: To investigate whether the near peripersonal space is a unitary multisensory representation of the peribody space or is organized in a modular fashion, separately representing different body parts. METHODS: Cross-modal extinction was used to assess right brain-damaged patients with left tactile extinction by presenting a combination of ipsilesional visual and contralesional tactile stimuli, both between homologous body parts (i.e., the two hands and sides of the face) and between nonhomologous body parts (i.e., right hand + left face and right face + left hand). RESULTS: Visual-tactile extinction observed in the near peripersonal space of homologous body parts was more severe than that obtained between nonhomologous body parts. In contrast, cross-modal extinction observed in the far peripersonal space was overall weak and comparable when stimulating homologous or nonhomologous body sectors. In addition, a clear near-far modulation of visual-tactile extinction was obtained only when stimulating homologous, but not nonhomologous, body parts. These findings were observed irrespective of the severity of unisensory tactile extinction. CONCLUSIONS: Near peripersonal space is not unitary but is functionally organized in modules and consists of at least two different spatial representations, one around the hand and another around the face, which might be selectively affected in patients with extinction.
Abstract: A large body of neuropsychological evidence has been recently provided showing that humans can code visual objects in nearby space through multisensory visuo-tactile integrative processes, which share several similarities with the functional properties of bimodal neurons documented in neurophysiological studies. In particular, the phenomenon of visuo-tactile extinction reveals that crossmodal integration may take place in a privileged manner within a limited sector of space closely surrounding the body surface, i.e. in the near peripersonal space. Here we report that visuo-tactile extinction can seemingly be obtained when a physical, transparent barrier is interposed between the patients' hand and a proximal visual stimulus. These findings show that visuo-tactile representation of peripersonal space can be formed despite the subject's explicit awareness concerning the physical impossibility for the hand to be touched. This phenomenon indicates that multisensory integrative processing can occur in a bottom-up fashion without necessarily being modulated by more 'cognitive' processes. Such integration may be functionally important for automatic reactions such as head turning or hand withdrawal.
