Social cognitive and neural mechanisms of food choice under the influence of food-related information

Food is the fuel of life. As such food stimuli are intensively processed by the human brain and the consequences of these processes, resulting in our food choice, have an essential impact on our life. Research suggested that food choice is largely guided by predominantly learned preference, and is likely to be influenced by information regarding the food (e.g., nutritional value) as well as by learned beliefs and associations (e.g., between a given food and its health value). This project aims at understanding at both behavioral and neural levels how these non-physiological factors might influence the food/drink choice and how they can be modified to improve our choice. Chapter 1 includes the literature review on 1) how semantic information influences implicit/explicit associations toward food/drink, 2) the predictive validity implicit/explicit associations on food/drink choice, 3) the behavioral and neural evidence of changing associations, choices, and impulsivity control toward food/drink by implementing a conditioning paradigm (e.g. evaluative conditioning). The motivation and the objectives of my Ph.D. project are also presented here. Chapter 2 contains Study 1 (Experiment 1 and 2). The first aim of the thesis is to understand how the association between a certain food and different concepts may guide our choices. This is addressed in Experiment 1 where I investigated how our choices can be predicted by preference and/or implicit associations between different constructs of interest (e.g., social status) and coffee and/or tea. People’s self-report preference, implicit and explicit associations between different social constructs and tea/coffee were measured. Results based on 22 Italian healthy adults indicate that they possess strong implicit associations between tea and low social status, and this association significantly predicted choice of tea. The second aim of the thesis is to investigate whether the associations between food/drink and certain constructs can be changed through a classical learning paradigm, evaluative conditioning (EC), in which the associations between target drinks/food and food-related information was manipulated. This approach allowed us to investigate a possible strategy of intervention that could improve drink/food choices. This is addressed in Experiment 2 whereby a within-subject design is employed with participants going through both EC-condition and control condition. Results based on 68 healthy adults show that the implicit associations between tea and high-social-status, as well as the preference towards tea, significantly increase after EC. Most importantly, the difference in implicit associations across conditions significantly predict the difference in choices of tea between conditions, indicating that changes in implicit associations determine changes in choice. Chapter 3 is dedicated to the third aim which is to identify the neural mechanisms underlying the changes in association after EC between foods and the concepts of healthiness and sustainability. To this end changes in neural markers were related to changes in food choice as well as personal eating habits and individual difference in restraint eating and impulsive behavior. In Study 2, I experimentally strengthened the association between the concept of unhealthiness/unsustainability and heavily-processed food, and between healthiness/sustainability and minimally-processed food. A semantic congruency task combined with the Electroencephalography (EEG) technique was used to investigate changes in neural activity of the N400 in incongruent trials. Results on 18 healthy adults derived by comparing neural signatures of incongruent trials between conditions demonstrated that the magnitude of the N400 in left dorsal lateral prefrontal cortex (DLPFC) for minimally-processed high-calorie food significantly increased after EC. Thus, EC can be considered as an effective method to strengthen the semantic association between foods and a given concept, indexed by the change of neural signature tracking the semantic conflict. This increased magnitude also positively correlated with the Barratt Impulsiveness Scale score, indicating that the more impulsive a person is, the greater the change in magnitude of the N400. Chapter 4 is devoted to address the fourth aim of the thesis that is to understand whether control of impulsivity over unhealthy food choice can be improved through the evaluative priming (EP) that is a variation of EC used in Study 2. Thus in Study 3, 15 healthy adults went through a pre-EP and a post-EP test including a Go/NoGo task combined with EEG. During EP, an increased subjective liking was found for Minimally-Processed Low-Calorie food images in evaluative block. For GNG tasks, at neural level, the averaged amplitude at left DLPFC for food images with evaluative priming was more negative in post-EP than in pre-EP GNG task. More negative N200 amplitudes were consistently found at left DLPFC in post-EP GNG task for Heavily-Processed Low-Calorie food as well as for Minimally-Processed Low-Calorie food. The behavioral and neural evidence showed the improvement of self-control towards food stimuli through evaluative priming. The possible role of left dorsal lateral prefrontal region in online value modulation and in integrating the stimulus feature with related information was identified, suggesting the self-control process based on deliberated thinking with symbolic representations and information operations. In Chapter 5 I summarized and discussed the main findings of my thesis. In short, my project provides the basic roadmap for understanding how food/drink related information affects cognitive and neural underpinnings of food/drink choices. Indeed, choices can be improved through modifying associations between food/drink and related information and thus healthy diets are encouraged. These results provide a potentially interesting research avenue well as possible interventions to modify and improve food/drink choices that could possibly be applied to individuals with eating disorders.