Date on Senior Honors Thesis

11-2025

Document Type

Senior Honors Thesis

Degree Name

B.S.

Department

Anatomical Sciences and Neurobiology

Degree Program

College of Arts and Sciences

Committee Chair

Chad Samuelsen

Committee Member

Robert Lundy Jr

Committee Member

John Gibson

Author's Keywords

Flavor; Odor; Taste; Chemosensory; Palatability; Consummatory Behavior

Abstract

Taste concentration is a key determinant of palatability. For example, higher concentrations of sucrose, a sweet taste, are typically preferred to lower ones, whereas the opposite is true for citric acid, a sour taste. Yet taste is not the only determinant of food preference. Flavor arises from the integration of taste and olfactory cues, and repeated exposure to odor-taste combinations can lead odors to acquire the hedonic value of their associated taste. However, the contribution of odor concentration, independent of taste, in guiding consummatory behavior is not well understood.

To address this, we conducted two experiments using a two-bottle brief-access task to examine preferences between low (0.01%) and high (0.1%) concentrations of the odor isoamyl acetate dissolved in water. In both experiments, preferences between the two odor concentrations were first assessed, followed by the same odor concentrations paired with a fixed concentration of either 0.1 M sucrose (Experiment 1) or 0.03 M citric acid (Experiment 2). Odor preferences were then re-tested after mixture experience.

Across all test blocks, rats consistently preferred the low odor concentration. However, following odor-taste mixture experience, the strength and direction of this preference changed according to the palatability of the paired taste. After pairing with sucrose, rats increased consumption of the high odor concentration relative to pre-mixture experience. After pairing with citric acid, rats increased consumption of the low odor concentration above pre-mixture levels. These findings demonstrate that odor concentration contributes meaningfully to consummatory preference. Although lower odor concentrations are generally favored, experience with odor-taste mixtures can shift these preferences depending on the taste’s palatability. These experience- dependent changes suggest that stimulus salience and hedonic value interact to shape odor-taste associations that guide consummatory behavior.

Lay Summary

Smell and taste work together to create the experience of flavor, yet little is known about how the strength of a smell influences what we choose to eat or avoid. This study examined how odor concentration, or how strong something smells, affects initial preferences and how those preferences change after the odor is paired with pleasant or unpleasant tastes.

Rats were given a choice between two concentrations of a banana-like scent: one weak and one strong. Their licking behavior was measured to assess which one they preferred to drink. Overall, rats always preferred the weaker scent, suggesting that the stronger one may have been too intense. Interestingly, these preferences shifted after the odors were paired with tastes. When the scents were mixed with something sweet, rats became more willing to sample the stronger scent. When they were mixed with something sour, the rats drank the weaker one even more.

These results show that odor strength not only affects how smells are perceived but also shapes how smells and tastes work together to influence flavor. In everyday terms, a strong smell can become more appealing or more off-putting depending on what kind of taste it has been paired with. This helps explain how our experiences with food shape perception, showing that whether a stronger smell is perceived as pleasant or unpleasant depends on what it was paired with in the past.

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