In this article I present examples of young children's interaction in collaborative group work in mathematics and consider how the children shared intentions, that is, how they influenced the thinking of another. By analysing the children's use of deixis as an aspect of indexicality, I examined how the students pointed out mathematical ideas to each other in different tasks. When the children engaged in tasks involving decision making about a representation or a sign, the children's use of deixis related to shared intentionality as they scrutinised the cultural meaning of the sign or representation.