Oral referral: On the mislocalization of odours to the mouth

- Oral referral is central to our understanding of multisensory flavour perception.
- Oral referral of orthonasal olfaction (known as orthonasal location binding) is modulated by taste intensity.
- Oral referral of retronasal olfaction is modulated by odour-taste congruency.
- Attentional capture by gustatory stimuli, and an inability to attend to olfactory component of flavours, is key to understanding oral referral.
- Oral referral may reflect a qualitative new type of multisensory phenomenon, involving confusion regarding which of one's senses have actually been stimulated.

Oral referral is central to multisensory flavour perception. The phenomenon, first described a little over a century ago, is characterized by the mislocalization of food-related olfactory stimuli to the oral cavity. Many researchers believe that it contributes to the widespread confusion concerning which sense really provides the information that is bound together in flavour percepts. In this review, evidence supporting the role of a number of factors that have been suggested to modulate oral referral, including tactile capture of olfaction, the relative timing of olfactory and gustatory stimuli, and gustatory capture (possibly involving prior entry) is critically evaluated. The latest findings now support the view that the oral referral of orthonasal aroma (what some have chosen to call orthonasal location binding) is modulated by taste intensity, while for retronasal odours, it is the congruency between the odour-taste(s) pairing that is key. Specifically, the more congruent a particular combination of olfactory and gustatory stimuli, the more likely the component unisensory stimuli will be bound together as a flavour object (or Gestalt) and, as a result, localized together to the oral cavity. The possible roles of attention, attentional capture, and the nutritional significance of the taste in the phenomenon of oral referral are also reviewed. Ultimately, the suggestion is made that oral referral may reflect a qualitatively different kind of multisensory interaction.