The extent and importance of children's opinion leading power is a phenomenon which concerns advertisers confronted with an advertising message for products consumed by children. Indeed, in this case one not only has to attract the children but also to win over those around them, and in particular their mothers, since the child, consumer of the products, is not always their purchaser. Two factors may therefore convince the mother to purchase the product: the advertising message and children's advice. In this first part of this essay, we shall attempt to provide elements to respond to this complex relationship between the advertising message, the child and its mother by measuring the effects of a frequent situation in television, the household viewing medium par excellence: "Joint viewing" of mother and child of an advertising message on the television. In the second part, we shall see how to measure precisely at which moments the mothers and children listen simultaneously to television and in particular advertising breaks.