Helping consumers with a front-of-pack label: numbers or colours? Experimental comparison between Guideline Daily Amount and Traffic Light in a diet building exercice

This paper contributes to the debate on front-of-pack nutritional labels. Because of their dissimilar formats, Guideline Daily Amount (GDA) and Traffic Light (TL) may trigger different responses among consumers. While GDA is comprehensive and cognitively demanding, information is coarser and more salient in TL. We implement an incentivized laboratory experiment to assess the relative performance of GDA and TL labelling schemes in assisting consumers to build a healthy daily diet. Participants must compose a daily diet, choosing from a finite set of products, and are paid a fixed cash amount only if the diet satisfies pre-determined nutritional goals. Goals correspond to the guideline daily amount values for different nutritional attributes, whose number varies from 1 (kcal) to 7 (kcal, fat, sugar, salt, fibre, vitamin C and calcium). Three different labels, GDA, TL and a combined GDATL are provided. Results show that GDA performs better than TL when subjects do not face time constraints. When time is limited however, TL and GDA have identical efficacy with 4 nutritional goals, and TL even outperforms GDA with 7 nutritional goals.