Interpreting interaction terms in econometric modelling is fussy. Even if logit or probit models are the most used modelling consumers' choice, they omit interaction e_ects among explanatory variables in the choice process. These blended e_ects are however declared in the modi_cations of consumption decision. The di_culty is to interpret coe_cients associated to these e_ects (interaction variables). To solve this problem, we propose a decision rule enforceable whatever the nature of the estimators. We build a convenient decision rule. We carry out an application of this decision rule to the choices of the wine consumers confronted with increasingly sophisticated products.