Leaving aside issues of nutrition, we usually judge a food by how much we like its flavour. But what is ‘like’? Ask a social psychologist and, after prolonged qualifications, they will probably tell you that ‘like’ is an attitude or a positive disposition towards something. So, if you wish to compare two foods in terms of liking or acceptability or preference, then degrees of positive disposition are what we are after. This doesn't sound very much like pure pleasure of the type that food can produce and yet ratings of liking are what are used by food companies to discover how consumers respond to foods and even to make decisions about whether or not a particular product should be launched into the marketplace.
Ratings of liking are thus a proxy for an emotion – pleasure – and for a behavior, food choice. This would be fine if we could be sure that ‘liking’ was a good proxy for either, but there is little evidence that this is the case. Here’s the problem. There is a substantial body of research and practical experience showing that liking ratings fail to predict later food choices. Very many reasons can be found to explain this, including the fact that rated samples are not representative of meals, that liking varies as a function of many variables – time of day, mood, and so on, and that choice is influenced by other variables apart from liking.
A relatively recent approach to this problem has been to ask if we are measuring the right thing. Are positive dispositions the sort of thing that are likely to reveal the next big product? I have posted previously about comfort and wanting. We recognize that a search for comfort is a particular feeling that will direct us towards specific types of foods, at least some of the time. Wanting, too, is a strong motivator that might underlie actual choices, irrespective of degree of liking. Of course, there are a multitude of emotions that we could measure, some of them perhaps quite important to us. Clinical psychologists and psychiatrists have been using standardized measures of emotion for some time, but the emphasis is unsurprisingly on negative emotions that are unlikely to be elicited by eating in most of us.
Compiling lists of independent emotional terms that might be more related to foods can of course be done and there are examples in the recent literature (see for example ). There is certainly evidence that rated emotions do discriminate between products, and perhaps in some cases better than liking ratings . But the issues to be addressed are many. Thus, how do we know that a food-elicited emotion is not mediated by the pleasure given by the food (as reflected by ‘liking’) rather than being a direct result of the food experience? This would be consistent with a great deal of research showing that pleasant stimuli of all kinds produce positive moods, which in turn might be described using words such as ‘cheerful’, ‘energetic’ or ‘friendly’ – all terms that have been used in emotion questionnaires.
Which brings us to another important issue: just how many emotions are there and how do we decide which ones to measure? On the basis of detailed cross-cultural comparisons, Ekman  for example has argued for the universality of a small number of emotions – happiness, anger, disgust, fear, sadness and surprise – and their associated facial expressions. If this is true, then it may be that your ‘cheerful’ is the same as my ‘friendly’, and that we actually both mean ‘happy’. In other words, perhaps these terms are all highly correlated with something called ‘positivity’. Searching for such key descriptors is not unlike the search for non-redundant terms in describing the sensory properties of products. But it is a more complex task to determine if a consumer’s rating of an emotion as irrelevant to their food experience represents actual lack of feeling or a poor fit between the word and what is actually felt. And that’s even without considering such seemingly bizarre concepts as “guilty pleasure”.
An emotion, though, is not just an internal feeling that needs a label. William James raised the question over a century ago of whether the other aspects of emotions – physiological responses and facial expressions – might not actually be primary, in that they precede the subjective feeling. To paraphrase his argument, do we run from a bear because we are afraid or are we afraid because we run from the bear? If the latter (and see  for evidence of this), then either facial expressions or the physiological correlates of emotions might be more direct measures of responses to foods.
While measuring facial expressions could be considered a more objective means of getting directly at emotions because they can be objectively verified, it is not true that expressions are spontaneous. We all manage our expressions, masking or modulating them depending on the context (or culture) we are in – a skill that is evident even in 3 year olds. Moreover, just how finely are smiles/frowns gradated? More than a 9 point liking scale? In a recent study , automated readings of positive (happy), neutral and negative (angry, disgusted) emotions in response to juice samples tracked ratings on a 9-point hedonic scale quite closely. In fact, the facial readings were able to differentiate between the samples, but not to a degree better than the scale.
Measures of physiology in response to foods are at a similar state of progress. Food scientists are now in many ways tackling some of the same issues that William James did at the end of the 19th century. Psychologists have recognized for the past century that quite different emotions share common physiological traits – e.g., both fear and anger are associated with increased heart rate. Following James, later theories of emotion emphasized the role that cognitions – interpretations – had in determining which emotional quality was associated with particular physiological changes for a given context. This was compellingly shown in Schacter and Singer’s classic 1962 experiment on the role of expectations in emotions . They showed that physiological arousal produced by an injection of epinephrine (adrenalin) could be interpreted as consistent with either anger or excitement, depending entirely on the context to which the subject was subsequently exposed. While there are good data showing that foods do elicit changes in physiology , once again the ability of these changes to predict food choice is unknown. In any case, the context in which the food is experienced is likely to be crucial.
My feeling is that there are a few years left in old liking scale yet. If we don’t receive sensory pleasure from a food, it is more than likely doomed to be a single purchase item; but the converse is not true. Liking therefore might best be seen as a measure that is necessary, but not sufficient, to predict food choices. The search is really for complementary measures that add some predictive power. The fact that emotion research has yet to add this tells us only that some key questions are in need of answers and that it is premature to expect successful applications without more basic research.
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2. Ng, M., C. Chaya, and J. Hort, Beyond liking: Comparing the measurement of emotional response using EsSense Profile and consumer defined check-all-that-apply methodologies. Food Qual Pref, 2013. 28: p. 193-205.
3. Ekman, P. and W.V. Friesen, Constants across cultures in the face and emotions. J. Pers.Soc. Psychol., 1971. 17(2): p. 124-129.
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