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

Abstract

Food is fundamental to survival and our brains are highly attuned to rapidly process food stimuli. Neural signals show foods can be discriminated as edible or inedible as early as 85 ms after stimulus onset1, distinguished as processed or unprocessed beginning at 130 ms2 and as high or low density from 165 ms3. Recent evidence revealed specialised processing of food stimuli in the ventral visual pathway4-6, an area that underlies perception of faces and other important objects. For many visual objects, present perception can be biased towards recent perceptual history (known as serial dependence7,8). We examined serial dependence for food in two large samples (n>300) that rated sequences of food images for either appeal or calories. Calorie ratings by males and females agreed closely but appeal ratings were higher in males. High calorie ratings were associated with high appeal, especially in males. Serial analyses testing if current trial ratings were influenced by the previous one showed both appeal and calorie ratings exhibited clear positive dependences (i.e., a high preceding rating increased current trial ratings). The serial effect for appeal was roughly twice that for calories and males showed a greater serial effect than females for both ratings. Serial amplitude was larger in those who reported a longer elapsed time since they last ate and was larger in the BMI>25 group compared to BMI<25. These findings square with recently found food selectively in 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.