So, here is the story of the methods that have been used to investigate motivation as told by Denise Redmond.
Focus on Robert Gardner and Wallace Lambert’s model of integrative motivation (1972) brought motivation to the forefront of studies in second language acquisition (hereafter SLA).
Based in the Anglophone and Francophone language communities of Montreal, Canada, Gardner and Lambert became interested in social processes that affect motivation.
Integration into language communities was at that stage an unproven theory and so they tested out by questionnaire.
Prior to Gardner and Lambert, motivation researchers in general education focused on individual characteristics, which were separate from social influences and easily measured by quantitative questionnaire surveys. (Dörnyei, 2005)