Summary: How much we enjoy a sweet drink can depend more on what we expect than on the drink’s actual ingredients. A new human neuroimaging study shows that the brain’s reward circuitry responds differently depending on whether people believe a beverage contains sugar or an artificial sweetener—meaning expectations alone can make sugar substitutes feel more rewarding.
Using functional MRI, researchers compared brain responses when participants received sugar or a non-nutritive sweetener while their expectations about the drink’s content were manipulated. When people expected sugar but were given a sweetener, activity in the dopaminergic midbrain—a central reward hub—rose significantly. By contrast, when participants expected an artificially sweetened “diet” drink, real sugar was rated as less pleasant. The results show that labeling and expectation can reshape both subjective enjoyment and neural encoding of sweet taste.
Key Facts
- The Expectation Effect: Believing a drink contained sugar increased enjoyment of artificial sweeteners and heightened midbrain activation.
- Negative Bias: Expecting an artificially sweetened beverage reduced how pleasant actual sugar tasted.
- Brain Center: The dopaminergic midbrain was identified as the region that reflects perceived nutrient value of sweet flavors.
- Nutrient-Focused Labels: Descriptions such as “nutrient rich” or “minimal added sugar” produced more positive expectations than terms like “diet” or “low calorie.”
- Study Sample: The research screened 99 healthy adults and scanned a selected sample with matched perceptions of sugar and sweetener to control for baseline taste differences.
Source: SfN
Elena Mainetto of Radboud University, Margaret Westwater of the University of Oxford, and colleagues at the University of Cambridge investigated whether changing people’s prior expectations could alter how much they enjoy beverages sweetened with sugar versus non-nutritive sweeteners.
Their findings are published in the Journal of Neuroscience.
The team screened 99 healthy adults, selecting participants who reported similar perceptual experiences for sugar and artificial sweeteners. This matching reduced sensory confounds so differences in enjoyment could be attributed to expectation rather than obvious taste differences.
In the experiment, participants generally reported liking artificial sweeteners about as much as sugar when asked, yet their reported pleasantness and brain responses changed when expectations were manipulated. When people were led to believe a drink contained artificial sweetener, they rated sugar-containing drinks as less pleasant. Conversely, when people expected sugar but received a non-nutritive sweetener, their enjoyment of the sweetener increased and midbrain responses were stronger.
Westwater explains that these findings suggest the dopaminergic midbrain may encode the expected nutrient or caloric value associated with sweet flavors. That is consistent with animal research indicating this brain region plays a role in sugar-seeking and nutrient-driven reward.
The study highlights expectation as a key factor shaping both behavior and neural processing of sweetness. These effects were most evident when sensory cues were unreliable, showing that what people think they are consuming can override or augment actual sensory input.
Westwater notes potential practical implications for dietary interventions: emphasizing positive aspects—such as calling a product “nutrient rich” or “low in added sugars”—might create more favorable expectations than labels emphasizing restriction like “diet” or “low calorie.” Framing healthier options in terms of what they contain rather than what they lack could make them more satisfying and easier to adopt.
Although the concept that expectation alters experience is not new clinically, the authors hope these neuroscientific results will encourage researchers and practitioners to consider expectation as an active ingredient in efforts to change eating behavior.
Key Questions Answered:
A: Expectation has powerful effects. This study shows that when people truly expect a sugary reward, midbrain activity increases even with a zero-calorie sweetener. The sensation of reward is partially driven by the anticipation of calories.
A: Labels matter. Terms like “diet” or “low-calorie” can signal nutrient scarcity to the brain and reduce activation in reward pathways, making otherwise palatable foods feel less satisfying.
A: Reframe how you talk about food. Describe choices in terms of their positive qualities—“nutrient-dense, low-sugar option”—rather than as deprived or inferior. That positive framing can prime your brain to find healthier foods more rewarding.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was provided by editorial 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 support weight management by lowering calorie intake. However, it remains unclear whether sugar and non-nutritive sweeteners produce distinct orosensory brain responses in humans and whether those neural responses are shaped by expectation.
To address these questions, the researchers screened 99 healthy adults and selected a subgroup who reported similar perceptual experiences for sugar and sweetener, removing potential confounds from sensory differences. During fMRI, participants received sugar- and artificially-sweetened beverages while the experiment manipulated their expectations in both probabilistic and deterministic conditioning paradigms.
Participants’ ability to distinguish sugar from sweetener depended on expectation, and expectation significantly influenced perceived pleasantness. Expectation altered midbrain responses during deterministic trials: mistakenly expecting sugar increased midbrain activation to sweetener relative to when sweetener was expected. Trial-by-trial confidence and pleasantness ratings were differentially associated with brain responses to sugar and sweetener.
These findings underscore the role of expectancy in the behavioral and neural encoding of sweet flavour, particularly when sensory cues are ambiguous. The expectation of sugar appears to boost the subjective value of non-caloric sweetener, potentially through flavour–nutrient conditioning that preferentially reinforces sugar.