1. A method of controlling the operation of an emotion synthesising device ( 2 ; 12 ) having at least one input parameter (Pi) whose value (Ei) is used to set a type of emotion to be conveyed, characterised in that it comprises a step of making at least one said parameter a variable parameter (VPi) over a determined control range, thereby to confer a variability in an amount of said type of emotion to be conveyed.