Summary: The pleasure we get from a sweet drink might have more to do with our expectations than the actual ingredients. A new study reveals that the brain’s reward system can be “tricked” into enjoying artificial sweeteners more simply by believing they contain real sugar.
Using fMRI scans, the team found that when participants expected sugar but received a sweetener, their dopaminergic midbrain—a key reward center—showed significantly higher activation. Conversely, expecting a “diet” drink made real sugar taste less pleasant. These findings suggest that the labels we use for healthy alternatives can fundamentally change how our brains process their value.
Key Facts
- The Expectation Effect: Falsely believing a drink contained sugar increased the enjoyment of artificial sweeteners and triggered greater midbrain activation.
- Negative Bias: When participants thought they were drinking an artificially sweetened beverage, they enjoyed real sugar significantly less.
- Brain Center: The study pinpointed the dopaminergic midbrain as the region responsible for processing the “perceived” nutrient value of sweet flavors.
- Nutrient vs. Diet Labels: Researchers found that emphasizing “nutrient-rich” or “minimal added sugar” could create more positive neural expectations than using terms like “diet” or “low calorie.”
- Study Scope: The research involved 99 healthy adults with similar baseline perceptions of sugar and artificial sweeteners.
Source: SfN
Elena Mainetto, from Radboud University, Margaret Westwater, from the University of Oxford, and colleagues at the University of Cambridge explored whether they could change how much people enjoy beverages containing sugar or artificial sweeteners by manipulating previous expectations about the drinks.
This work is published in Journal of Neuroscience.
The researchers screened 99 healthy adults averaging 24 years of age, selecting those with similar perceptions of sugar and artificial sweeteners.
Participants largely reported liking artificial sweeteners as much as they liked sugar, but, notably, the researchers found that they could alter beverage pleasantness by manipulating people’s expectations. When participants falsely believed they were drinking a beverage containing artificial sweeteners, they enjoyed sugar-containing drinks less.
Conversely, when people falsely expected drinks to contain sugar, this expectation increased their enjoyment of artificial sweeteners, which coincided with increased activation of a brain area related to reward.
Says Westwater, “This could mean that this brain area, the dopaminergic midbrain, processes increased nutrients or calories of sweet flavors, which supports rodent work showing that this brain region is important for sugar seeking.”
According to the researchers, this work emphasizes the importance of expectancy in both behavioral and neural correlates to sweetness processing.
Westwater elaborates on potential implications for dietary interventions, saying, “If we emphasize that healthier food alternatives are ‘nutrient rich,’ or have ‘minimal added sugars,’ this may create more positive expectations than using terms like ‘diet’ or ‘low calories.’ This may help people align their food choices with the brain’s preference for calories while supporting behavior change.”
While Westwater acknowledges that this information isn’t new in a clinical sense, she hopes that the findings of this study shape how neuroscientific researchers look at diet and eating habits.
Key Questions Answered:
A: Your brain can! The study shows that if you truly expect a sugary reward, your midbrain fires up even if you’re drinking a zero-calorie sweetener. The “trick” is in the expectation of calories, which the brain’s reward center craves.
A: It’s partly psychological branding. The term “diet” or “low-cal” signals to your brain that it’s about to be deprived of nutrients. This negative expectation actually dampens the activation of your reward pathways, making the food seem less satisfying than it actually is.
A: Change how you talk to yourself about food. Instead of saying “I’m having a diet snack,” try “I’m having a nutrient-dense, low-sugar alternative.” By focusing on what the food has (nutrients) rather than what it lacks (calories), you can prime your brain to find the healthy choice more rewarding.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this taste perception research news
Author: SfN Media
Source: SfN
Contact: SfN Media – SfN
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Expectation modulates the hedonic experiences of and midbrain responses to sweet flavour” by Elena Mainetto, Margaret L. Westwater, Hisham Ziauddeen, Kelly M.J. Diederen and Paul C. Fletcher. Journal of Neuroscience
DOI:10.1523/JNEUROSCI.1121-25.2026
Abstract
Expectation modulates the hedonic experiences of and midbrain responses to sweet flavour
Non-nutritive sweeteners are sugar substitutes that may promote weight management by reducing an individual’s calorie intake. It is, however, unclear whether (i) sugar and non-nutritive sweetener elicit distinct orosensory responses in the human brain, and (ii) whether the neural responses to these flavours are modulated by expectancy.
Addressing these questions has direct relevance to our understanding of food choice behaviour and how it may be modified in dietary interventions. We screened N=99 healthy adults of either sex to select a sample (N=27, M[SD]age = 24.25[2.94] years) who reported similar perceptual experiences of sugar and sweetener, thus removing a potential confound of sensory differences, for fMRI scanning.
While scanning, they received sugar- and artificially-sweetened beverages in two conditioning paradigms, which manipulated participants’ expectation of flavour delivery: first in a probabilistic and second in a deterministic way.
Participants’ ability to accurately distinguish sugar from non-nutritive sweetener depended largely on their expectations, which also significantly affected the perceived pleasantness of each flavour.
Expectation altered brain responses to flavour delivery during the deterministic task only, where the (mistaken) expectation of sugar significantly increased midbrain responses to sweetener compared to when sweetener was expected.
Trial-wise confidence and pleasantness ratings differentially scaled with brain responses to sugar and sweetener delivery.
These results highlight the importance of expectancy in both the behavioural and neural encoding of sweet flavour, particularly when sensory information is unreliable.
The expectation of sugar appears to increase the subjective value of noncaloric sweetener, which may result from flavour-nutrient conditioning that preferentially reinforcers sugar.
