Since the 1970s, a great number of experimental and ethnomethodological studies have brought out the fact that social interaction influences cognitive development. However, two major questions remain: what is the true nature of this influence and what are the most relevant methods to catch it? The contributions of this Special Issue are in keeping with these concerns regarding more adequate methods to describe and analyze, within a same functional unit, at least three levels of comprehension of socio-cognitive phenomena: the individual‘s cognitive functioning; the socio-cognitive functioning of the dyad or the small group; and finally, the way the first two elements are mediated by discursive activities.