Olfactory conditioning reinforced by saccharin in humans: Influence of prop taster and sweet liker status

Repeated retronasal exposure to novel food odours with sweet and bitter tastes can lead to subsequent changes in orthonasal liking and sensory experience of the taste-paired odours. PROP tasters have been reported to rate low concentrations of saccharin as more bitter and less sweet than do PROP non-tasters. We therefore predicted that acquired liking for, and sweetness and bitterness of, odours conditioned by association with saccharin would vary depending on PROP taster status. 87 volunteers evaluated two novel odours before and after co-experience of one odour with 4 mM/l saccharin and the second with water. PROP taster status was assessed from the intensity of 3.2 mM PROP relative to 1.0 M NaCl, and sweet-liker status from liking ratings for 0.21 and 0.83 M/l sucrose and 0.0004 M/l and 0.0010 M/l saccharin. Liking for the saccharin-paired odour increased in sweet likers but decreased in sweet-dislikers. Overall liking change also varied with PROP taster status, with both odours rated less pleasant post-training in the super-taster and taster but not non-taster groups. The saccharin-paired odour was rated sweeter post-training, regardless of PROP taster or sweet-liker status. PROP super-tasters rated the saccharin-paired odour as more bitter post-training, in-line with enhanced bitterness of saccharin in this group. These data confirm that sensory and hedonic changes operate independently olfactory conditioning, and are influenced by individual differences in sensitivity to bitter and sweet stimuli.