Recent reviews of synesthesia concentrate upon rare neurodevelopmental examples and exclude common olfactory-induced experiences with which they may profitably be compared. Like the neurodevelopmental synesthesias, odor-induced experiences involve different sensory modalities; are reliable, asymmetric (concurrents cannot induce), and automatic; and the inducer-concurrent relationship is learnt. Unlike neurodevelopmental synesthesias, these experiences are universal and their synesthetic nature goes unrecognized. Olfaction's ability to universally induce concurrents may result from its unique neuroanatomy, affording dual access to neocortex. We propose that concurrents arise here via a twofold process: by direct neocortical activation, which recovers a configural memory, and by attribution of this memory to the olfactory modality by thalamic attentional processes. The implications of this for other forms of synesthesia are then examined.

Prior exposure to either a pleasant or unpleasant context may affect later hedonic judgments of a common target stimulus. We explored whether this effect translates into behaviour in the chemical senses. In experiment 1 participants experienced either a pleasant or unpleasant set of odours or pictures, followed by an unfamiliar odour. After self-report hedonic evaluations of the odour, participants were allowed to drink it in solution, followed by a further evaluation of its flavour. Participants reported liking the odour less after smelling pleasant odours and drank less of it too, relative to the unpleasant context. There was no differential context effect for emotive pictures. Experiment 2 replicated these effects, but also included a no-context control. This revealed that the consumption effect was localised to the pleasant olfactory context, whilst contextual effects for liking ratings were primarily localised to the unpleasant olfactory context. In conclusion, hedonic context affects both self-report and behaviour, but not in the same way.

This study examined the impact of odor naming and imagery ability on the capacity of female participants to form odor images, as indexed by a novel olfactory repetition priming task. Experiment 1 involved three conditions - olfactory and visual imagery priming, and a no-prime control. Odor imagery priming was only obtained in good odor namers. Experiment 2 used the same conditions, but altered the nature of the hit-rate trials to test how odor imagery might facilitate performance in good odor namers. Odor imagery priming was again obtained only in good odor namers and this effect appeared to result from generic activation of olfactory processing caused by trying to imagine a smell. Experiment 3 examined whether this latter effect might be generated semantically, but no evidence for this was obtained. Together, these findings suggest that trying to form an odor image can facilitate performance by producing a generic state of activation, which only benefits existing odor-name associations. While this effect is mediated via perceptual processes it may occur independently of a conscious image.

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