Understanding affective response to food using facial electromyography

: a preliminary look at individual differences

Abstract

Understanding consumer responses to food can aid the success of newly developed food products. Consumer responses can take many forms, with traditional consumer affective testing typically capturing self-reported hedonic liking of food products. Research has highlighted the importance of emotion-related responses to food choice and eating behaviour and has suggested that, although self-reported hedonic measures are insightful, using complementary methods that capture the temporally dynamic nature of food interaction may offer a more complete picture of the consumer experience. Such methods include facial electromyography, which can pick up changes in the facial muscles, often in the corrugator, levator, and zygomaticus muscles, as these have been shown to be related to affect.

Further literature has also indicated the benefits of focusing on individual differences to better understand food-related responses. For instance, a growing body of research looking at challenging, selective, or disordered eating behaviour has highlighted links with autistic traits in the general population, and studies on clinical groups have found autism often presents with sensory sensitivities, which can affect eating behaviour. Furthermore, the autistic trait ‘attention to detail’ has been specifically found to be associated with altered, non-typical eating behaviours. Attention to detail has been suggested as being driven by hypersensitivity. However, at present, there are no published studies investigating attention to detail or hypersensitivity and their associations with affective response to food in the general population. Such insights would be helpful to the food industry for new food product development and would also be of interest to researchers and clinicians who work with individuals with challenging eating behaviours.

This PhD thesis sets out by offering the reader clarity on the facial muscles most worthy of being targeted for associations with conscious hedonic evaluation in food-related paradigms, by reporting the results of a systematic review of the existing literature. Further empirical evidence is offered in five separate studies including food viewing paradigms and oral processing paradigms where the product being sampled is a complex food product. The PhD further offers an exploratory investigation into the individual differences relating to attention to detail and hyper-sensitivity and their associations with affective and sensory responses to food. This investigation is then extended in a series of controlled experiments to systematically research associations between food response and autistic traits, which are present in the general population, including social skills.
The findings of this thesis suggest the corrugator is the muscle most worthy of investigation in food paradigms where associations with self-reported hedonic liking are being sought; however, these findings also suggest that although this association appears robust it is weak, and the use of other complementary methods would allow for clearer insight into consumer affective response to food. Zygomaticus activity was also found to have a significant but weak association with hedonic liking of food stimuli in the two empirical studies examining responses to food pictures.

Higher attention to detail scores were found to have an association with reduced levator activity while viewing palatable food pictures; however, when investigating food pictures with a wider variation in palatability, as was done in the larger study, no associations between levator activity and attention to detail were found. Attention to detail scores were also found to be positively associated with corrugator reactivity during the oral processing of a sweet dark chocolate sample. Self-reported hyper-sensitivity was not found to be associated with self-reported hedonic liking, self-reported sensory perception, or facial activity during food interaction in any of the studies.

Interestingly, exploratory analyses suggested the trait which had the clearest association with self-reported sensory perception during oral processing of dark chocolate, as well as an association with facial activity during the viewing of food pictures, was social skill. These findings are discussed and integrated into the existing literature and potential future research directions are offered. This PhD starts to fill a gap in the existing literature on human affective responses to food and, as such, will be of interest to the scientific community as well as individuals working in practical settings.

Date of Award	Oct 2022
Original language	English
Awarding Institution	Abertay University
Supervisor	John Grigor (Supervisor), Andrea Szymkowiak (Supervisor) & Jon Wilkin (Supervisor)