Task-based interface design principles (TBI) were evaluated as a framework for designing effective nutritional labels. In two experiments a total of 123 people assembled a packed lunch, selecting components using labels in GDA or TBI format, or when given only the names of the foods. Study 1 found that a GDA label helped people make healthier choices than the product name alone, but that for a number of types of food, most people would make the same decision with or without a GDA label. Moreover, decisions were much faster when made with the name alone. Study 2 introduced a TBI label in the context of the more specific task of keeping the salt in the lunch under 1g. TBI and GDA labels reduced salt equally, but only the TBI label was as quick as the name alone. Labels that are aligned with people's specific objectives are more efficient. TBI is a potentially useful framework, that can be deployed using mobile computing.
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