The role of congruency and pleasantness in odor-induced taste enhancement.

Although odorants and tastants are perceived by two different senses, the rated intensity of a tastant may increase if an odorant is added. The size of the odor-induced taste enhancement is said to depend on the perceptual similarity between the tastant and the odorant, and on the task instruction which affects subjects' working concepts of attribute categories. It is investigated whether congruency or pleasantness (halo-effects) can replace perceptual similarity in accounting for odor-induced taste enhancement. Sweetness intensity, pleasantness, and degree of congruency are determined for three sucrose/odorant combinations. Odor-induced enhancement is found only for congruent mixtures (sucrose/strawberry and sucrose/lemon). In addition, highly congruent mixtures are more pleasant than expected under additivity. The pleasantness judgments for incongruent combinations (sucrose/ham) follow a subtractive rule. The congruency ratings can account for a significant part of the pleasantness ratings, but not for the degree of sweetness enhancement. Also, the pleasantness ratings are not related to the degree of enhancement. Therefore, congruency or pleasantness ratings cannot replace similarity ratings in accounting for odor-induced taste enhancement.