Summary: New research shows that when people evaluate food images for appeal or calorie content, their judgments are biased by the food they just saw. This phenomenon—called serial dependence—means that a highly rated item makes the next item more likely to be rated highly, while an unappealing item pulls subsequent ratings down. These sequential biases shape everyday food choices and have implications for healthier eating strategies, marketing, and clinical treatments for eating disorders.
A large study by researchers at the University of Sydney finds that food perception is not made in isolation: our most recent impressions influence the next. The research, published in the journal Current Biology, was led by Professors David Alais and Thomas Carlson from the University of Sydney’s School of Psychology, in collaboration with Professor David Burr at the University of Florence.
Key Facts:
- Serial dependence causes food ratings to be biased toward the previous judgment.
- A high appeal or calorie rating increases the chance that the next item will receive a higher rating, and vice versa.
- Effects were consistent across participants and were similar for ratings of appeal and calories.
- Findings can inform menu design, food marketing, and cognitive therapies for eating disorders and overeating.
Source: University of Sydney
The researchers ran experiments involving more than 600 participants who rated sequences of food images for both perceived appeal and perceived calorie content. Rather than each evaluation standing alone, the ratings showed a clear serial dependence: a participant’s rating for one picture systematically nudged the rating for the next picture in the same direction.
Serial dependence appears whenever people make a series of rapid, related judgments. In the food domain, if someone gives a high appeal rating to one dish, they are more likely to give a higher rating to the next dish they view—even if the two items differ in calories or intrinsic appeal. The reverse also holds: viewing an unappealing item tends to lower the rating of what follows.
Lead author Professor Alais noted that the conditions that produce serial dependence in the lab resemble everyday scenarios such as scrolling through a food-delivery app or flipping through a menu. “Serial dependence, therefore, might be affecting millions of food choices every day,” he said. The bias is subtle, but cumulative: one rating nudges the next, creating chains of linked evaluations that can shape preferences and choices over a browsing session.
The study found some sex differences in mean ratings—men tended to give slightly higher ratings to high-calorie foods—but the serial dependence effect itself was robust across sexes. Ratings of calories were consistent across participants, while appeal ratings varied more, reflecting personal taste. Still, both types of ratings displayed positive serial dependence: higher values on one trial produced positive biases on the next.
Co-author Professor Carlson highlighted the speed of visual calorie perception: earlier work indicates the visual brain encodes perceived caloric content in milliseconds. Future research will investigate how these fast visual processes interact with serial dependence to influence decisions about what and how much to eat.
Applications of this work are broad. For restaurateurs and food marketers, thoughtfully ordering menu items—placing highly appealing or calorie-rich options earlier in a sequence—could shift consumers’ perceptions and purchasing behavior. Clinically, understanding serial dependence offers another sensory-level tool that could complement cognitive and behavioral therapies for obesity, compulsive eating, bulimia, and related conditions. Therapists might design interventions that disrupt or re-route sequential biases to help clients make healthier choices.
The team points out that serial dependence is not unique to food judgments: similar sequential biases have been observed in other domains, such as attractiveness ratings on dating apps and evaluations of artworks. This consistency suggests a general principle of perception: our brains tend to smooth experience over time by incorporating recent history into current judgments.
About this psychology research news
Author: Katie Spenceley
Source: University of Sydney
Contact: Katie Spenceley – University of Sydney
Image: The image is credited to Neuroscience News
Original Research: Open access. “Positive serial dependence in ratings of food images for appeal and calories” by David Alais et al., Current Biology
Abstract
Positive serial dependence in ratings of food images for appeal and calories
Food is essential to survival, and the visual system is finely tuned to rapidly detect and evaluate food. Neural responses can discriminate edible from inedible items within roughly 85 ms, distinguish processed from unprocessed foods by about 130 ms, and signal high versus low energy density from around 165 ms. Recent evidence points to specialized food processing in the ventral visual pathway, the same system that supports face and object recognition.
This study measured serial dependence in two large samples (each n > 300) who rated sequences of food images for either “appeal” or perceived “calories.” Calorie ratings were highly consistent between participants and comparable across sexes. Appeal ratings showed greater individual variation and were, on average, higher in males than females, with high-calorie foods tending to receive higher appeal ratings, especially among men.
Crucially, both calorie and appeal ratings exhibited clear positive serial dependence: higher-rated stimuli on previous trials biased subsequent ratings upward, and lower-rated stimuli biased them downward. These effects were consistent across participants and between sexes. The results align with evidence for food-selective processing in visual cortex and introduce serial dependence as a sensory-level mechanism that can influence food decision-making and complement cognitive approaches in dietary interventions.