Professor Raffaella Rumiati shares some insights into food recognition and eating behaviours that are emerging from food neuroscience research at SISSA
In recent years there has been growing interest in finding out how our brain processes food cues and directs our food choices. Food is essential because it provides the energy that keeps us alive, but it is also associated with hedonic experiences.
Although some substantial knowledge has been acquired to date about the mechanisms underlying food perception and choice in humans, food cognitive neuroscience is a field that is still in its infancy. In addition to advances in basic research, this area of enquiry has a lot of translational potential. Disorders in eating behaviours have become widespread at the population level, especially in developed, industrialised countries where food availability is overwhelming. The statistics on eating disorders are such that they now constitute a growing preoccupation for public health systems and societies in general. Researchers contribute towards alleviating these concerns by providing findings that can hopefully be translated into successful treatments.
For all these reasons, food has become central to the research interests of our ‘Neuroscience and Society’ laboratory at the International School of Advanced Studies in Trieste, Italy. To begin with, we developed our own database – FoodCast Research Image Database (FRIDa) – that contains about 900 original pictures of food and non-food stimuli that every researcher can freely access. FRIDa has been validated with a sample of neurologically intact participants on domain-general variables, such as valence and familiarity, but also on some domain-specific variables such as perceived calorie content, while controlling for brightness and high frequency power.
We carried out several studies using different methodologies and techniques to answer food related questions. To begin with, we asked ourselves how the intrinsic characteristics of food – such as whether it is natural food or manufactured, or its colour – influence our recognition.
Food recognition in people with aphasia and dementia
In a first study published in 2016 in a special issue of ‘Brain and Cognition’ completely dedicated to food neuroscience, we administered several tasks in order to evaluate the ability of patients with primary progressive aphasia (PPA) and with Alzheimer’s disease (AD) to recognise food and non-food pictures taken from FRIDa. Food included natural items such as an apple or a tomato, or manufactured items such as a hamburger or pasta, while non-food items were either tools or natural non-edible things, like a stone.
Overall, patients were less accurate than healthy individuals, with PPA patients being generally more impaired than AD patients, particularly when they named pictures. Interestingly, food was recognised more accurately than non-food items in 2 out of 3 tasks. Moreover, AD patients named transformed food more accurately than natural food. Thus, recognition particularly of transformed food tends to be more resilient to brain damage. We think that this pattern of results can be due to the critical role of food in survival: Food is the fuel of life. Another interesting finding of this study is that the names of foods that are acquired earlier coincide with edible items that are richer in calorie content (i.e. age of acquisition). This is the first time that, in addition to psycholinguistic variables, calorie content has been considered in lexical-semantic processing.
Evolution vs the modern world
Previous evidence showed that trichromatic primates are very efficient in judging ripeness of fruits or edibility of leaves. This means that their visual system allows these animals to see the environment in colours and, more importantly, to distinguish red and green nuances in fruits and leaves that are generally associated with higher energy or protein content. This ability clearly facilitates foraging and, as such, confers to trichromatic animals an evolutionary advantage.
Thus, the aim of a second study that was published at the end of last year in ‘Scientific Reports’ was twofold: To establish i) whether colour plays a role also in human food evaluation, and ii) whether this strategy is viable for both natural and transformed food. To this end, we had healthy participants rate how arousing they perceived foods and non-food items to be, with arousal being defined as a proxy for wanting that also mediates preparatory behaviour. As the underlying working hypothesis was that the effect of colour on arousal and calorie content is derived from the relationship between energy-content and colour in natural food, but not in transformed food, participants also rated the perceived calorie content, as well as the level of transformation of food stimuli.
After controlling for all possible confounding variables at the level of stimuli or individuals, we observed very clear-cut effects: Participants are more attracted to natural or transformed food characterised by high reddish-nuances and value less the food items with higher green-colour content. These findings confirm that humans, likewise non-human primates, use colour to guide their food evaluation. But while relying on colour represented a winning strategy for our ancestors who had to search for food in an environment where it was not so abundant, in our time this hard-wired mechanism seems to bias our food evaluation, by extending this heuristic from natural food to transformed food. In fact the participants in our experiment were generally more attracted to any food that contains high reddish-nuances, irrespective of its level of transformation.
Towards sustainable eating behaviours
There are many more findings coming from our research programme on food neuroscience. One research strand has been building on the relevance of considering food not as a unique category, by investigating for instance the level of transformation of food using other techniques such as EEG and fMRI in healthy individuals. Another explored how the characteristics of the perceiver, such as the BMI, or of the perceiver’s habits, as in the case of restraining eating, may modulate food recognition and evaluation. Much attention in our lab is also being given to better understanding the food behaviours of patients with Parkinson’s disease, with particular reference to wanting and liking mechanisms, as they seem altered in this population.
A conclusive message is that to nudge individuals to adopt sustainable eating behaviours we must understand better how individuals recognise and evaluate food. Even large-scale policies cannot be implemented with the hope of success if they are not scientifically guided.
Professor Raffaella I Rumiati
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