Somatic influences. Social influences

Naturally enough, it has mostly been biological psychologists and medical physiologists who have sought to characterize physiological influences on human appetite. As we have seen, however, this is not a biological issue in any sense that escapes thorough empirical analysis of the cognitive and psychosocial influences on the observed food acceptances (or on verbal data predictive of ingestion). On the other hand, progress on this set of issues cannot be made either by an exclusively psychological approach that lacks effective manipulations or by measurements of the hypothesized processes under the skin. As yet, expertise in both human physiology and cognitive psychology, with access to the necessary facilities, is rare in one person or in an effective collaboration. As a result, disappointingly little can presently be said that is definite about biological aspects of food acceptance in human consumers.

As was well recognized 20 years ago, although it has often been neglected more recently, the main methodological problem is that physiological influences on food acceptance are normally thoroughly confounded with cognitive influences. Emptying of the stomach is rather precisely related to awareness of the lapse of time since the last meal. Filling of the stomach during a meal is even more closely associated with the perceived amount eaten. Different postingestional effects of the nutrient composition of foods cannot be separated from differences in the “image” of those foodstuffs and their sensed constituents.

Unfortunately, most of those experiments that have exposed postingestional influences of food eaten at a meal, by disguising its amount or composition, have recorded only the amounts or temporal patterns of subsequent food intake and have not attempted to measure or control postingestional effects or their timing. Differences in acceptance pattern among conditions (or people) fail to identify the somatic influences that are operative.

A sufficiently high dose of glucooligosaccharides produces a suppression of actual and rated food acceptance after 20-30 minutes. At that time most of this carbohydrate has left the stomach and glucose is being absorbed rapidly. This is consistent with the suppression of appetite by energy production from the glucose (from animal experiments, thought to be in the liver). Action on receptors in the intestinal wall has not been excluded, though. This decrease in food acceptance is no greater than that related to guessing that caloric content of the meal is high; this shows the power of autosuggestion.

Infusion of fat into the small intestine has been shown to delay the rise of rated hunger sensations, whereas this sort of effect is not produced by intravenous infusion. This points more conclusively to the importance of gut wall stimulation among the physiological influences on human food acceptance.

Social influences. Consumer survey data and sales trends collected by the food business provide material for elaborate discussion of socioeconomic, interpersonal, and cultural influences on food acceptance. The psychological content would, however, be largely intuitive and speculative. This is because, once again, little research has been done that tests how each consumer makes purchasing decisions about foods, let alone chooses when, what, and how much to eat. Thus, the important task is to put social influences on acceptance on the same scientific footing as sensory influences.

Interpersonal and cultural influences are not inherently any less objective than sensed food qualities or perceived physiological processes. The difference between social factors and the sensory and somatic factors is that many social influences are mediated linguistically; that is, they exist only because of communicable symbolic meaning. As a result they are not effectively describable in purely physicochemical terms. Nevertheless, the words or sentences applied to the food on the package or in the advertisement are entirely objective potential influences on speakers of the language who have been educated into the constructs being communicated. The same applies to nonverbal symbols in the pictorial “language” being used.

Some symbols have inherent potential for scaling on a dimension of influence (e.g., price, shelf-life date, and perhaps recommended storage temperature). These and essentially nominal labels must be scaled, however. Scaling consists of analyzing out the relative strengths of influence of the labels on one or more underlying dimensions accounting for a descriptive or acceptance response. This is most realistically and hence effectively achieved by mapping the labels onto differences in response, in the same way that influences are identified from inherently graded physical influences (e.g., food composition).

A neat illustration is provided by the interaction of the labeled nature of a food constituent with the taste of that constituent, in a manner that is rational to the meaning of the label. The label for a sweetener might be “low calorie” or “sugar,” for example. The influence of the label should multiply by the level of sweetener to generate an estimate of calorie content. This is indeed observed in some consumers, so that the fattening potential of the food and its influence on food choice are rated to be higher for a strongly sweettasting food labeled “sugar-sweetened” than can be accounted for by the addition of the effects of the sugar label alone and sweetness alone. In other consumers, labeled calories and sweetness are treated as distinct dimensions or even added onto a single dimension.

Similar interactions of the effect of prices with other salient attributes of the range of alternatives can provide realistically scaled price-purchase elasticity functions. In recent years such trade-offs between brand attributes have been characterized by nonmetric methods of group data analysis. For much the same datagathering cost the individualized discrimination approach to cognitive model testing gives precise quantitative diagnoses of attribute interactions in each consumer sampled. The results not only imply practical recommendations for food design, they also tell us something theoretical about the mechanisms of acceptance in the tested situation.

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