Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden.
Monell Chemical Senses Center, Philadelphia, PA 19104, USA.
Chem Senses. 2021 Jan 1;46. doi: 10.1093/chemse/bjab003.
Repeated exposure can change the perceptual and hedonic features of flavor. Associative learning during which a flavor's odor component is affected by co-exposure with taste is thought to be central in this process. However, changes can also arise due to exposure to the odor in itself. The aim of this study was to dissociate effects of associative learning from effects of exposure without taste by repeatedly presenting one odor together with sucrose and a second odor alone. Sixty individuals attended two testing sessions separated by a 5-day Exposure Phase during which the stimuli were presented as flavorants in chewing gums that were chewed three times daily. Ratings of odor sweetness, odor pleasantness, odor intensity enhancement by taste, and odor referral to the mouth were collected at both sessions. Consistent with the notion that food preferences are modulated by exposure, odor pleasantness increased between the sessions independently of whether the odor (basil or orange flower) had been presented with or without sucrose. However, we found no evidence of associative learning in any of the tasks. In addition, exploratory equivalence tests suggested that these effects were either absent or insignificant in magnitude. Taken together, our results suggest that the hypothesized effects of associative learning are either smaller than previously thought or highly dependent on the experimental setting. Future studies are needed to evaluate the relative support for these explanations and, if experimental conditions can be identified that reliably produce such effects, to identify factors that regulate the formation of new odor-taste associations.
重复暴露可以改变味道的感知和愉悦特征。在这个过程中，味觉的气味成分受到与味觉同时暴露的影响，这种联想学习被认为是核心。然而，由于单独暴露于气味本身，也会发生变化。本研究的目的是通过重复呈现一种气味与蔗糖一起，以及单独呈现另一种气味，将联想学习的影响与没有味觉的暴露影响区分开来。60 名个体参加了两次测试会议，两次会议之间间隔 5 天的暴露阶段，在此期间，刺激物作为口香糖中的香味剂呈现，每天咀嚼三次。在两次会议上都收集了对气味甜度、气味愉悦度、气味强度增强的味觉感知以及气味与口腔的关联的评价。与食物偏好受到暴露调节的观点一致，气味愉悦度在两次会议之间增加，而与气味（罗勒或橙花）是否与蔗糖一起呈现无关。然而，我们在任何任务中都没有发现联想学习的证据。此外，探索性等效性测试表明，这些效应要么不存在，要么在幅度上微不足道。总之，我们的结果表明，联想学习的假设效应要么比之前认为的要小，要么高度依赖于实验环境。需要进一步的研究来评估这些解释的相对支持，并确定是否可以确定产生这种效应的实验条件，以确定调节新气味-味道关联形成的因素。
