With the objective of discussing how language ability emerges in infants through everyday interaction with parents playing with toys together, we analyzed video recordings of toy-based interactions between an infant-mother pair made over a 6 - 24 month period. The analysis focused on "supportive interactions by the parent with the infant," and "exploratory and performatory interaction with objects by the infant." We observed the interactive process between mother and child with toys by firstly recording the continuous progression of actions and speech by both the mother and infant. Secondly, we described the interactive development accompanying changes in the position of objects, and thirdly, we described the development of cooperative activities between both mother and infant.