Positive serial dependence in ratings of food images for appeal and calories

Food is fundamental to survival, and our brains are highly attuned to rapidly process food stimuli. Neural signals show that foods can be discriminated as edible or inedible as early as 85 ms after stimulus onset,1 distinguished as processed or unprocessed beginning at 130 ms,2 and as high or low density from 165 ms.3 Recent evidence revealed specialized processing of food stimuli in the ventral visual pathway,4,5,6 an area that underlies perception of faces and other important objects. For many visual objects, perception can be biased toward recent perceptual history (known as serial dependence7,8). We examined serial dependence for food in two large samples (n > 300) who rated sequences of food images for either “appeal” or “calories.” Ratings for calories were highly correlated between participants and were similar for males and females. Appeal ratings varied considerably between participants, consistent with the idiosyncratic nature of food preferences, and tended to be higher for males than females. High-calorie ratings were associated with high appeal, especially in males. Importantly, response biases showed clear positive serial dependences: higher stimulus values in the previous trials led to positive biases, and vice versa. The effects were similar for males and females and for calories and appeal ratings and were remarkably consistent across participants. These findings square with recently found food selectively in the visual temporal cortex, reveal a new mechanism influencing food decision-making, and suggest a new sensory-level component that could complement cognitive strategies in diet intervention. •Ratings of food images for calories or appeal are not serially independent•Both rating types show an “attraction” bias toward the previously seen food•For appeal ratings, the bias declined with hunger and age and increased with BMI•This perceptual bias in food appraisal could augment existing clinical interventions Alais et al. show that ratings of food images for appeal or calories are biased toward foods previously seen, with current ratings being higher after a highly rated food (and vice versa). Many visual stimuli show this bias, thought to arise at sensory levels. This bias could be used to nudge sensory food responses higher or lower to moderate food behaviors.