A study examined developmental differences in students' recognition of the types of explanations that help most in mathematics peer-group interactions. Scripted interactions of eight male and eight female dyads working on math problems were videotaped. In each interaction one actor in the dyad would request non-specific assistance and the other would provide one of four types of responses: (1) answer, (2) procedure, (3) procedure and justification, or (4) procedure and demonstration. Subjects, 62 third and fifth graders, worked on each of the math problems, were shown the videotape of the dyad working on the same problem, then rated the degree to which they thought the reply helped the other actor to understand the math work. Sixty adults who read the scripts of the interactions also indicated how much they thought the response helped the other actor. Results indicated age-related differences in children's differentiation among different types of replies to requests for information. Older subjects made greater distinctions between replies that only provided them with an answer and those that provided them with information about the process of problem solving. In addition, older subjects were better able to verbalize this distinction. They referred more often to the need for a response that contained information that would teach them the process and allow generalization to future math problems. Appendices provide girl and boy scripts for 3rd and 5th grade stimuli and a description of the coding system for justification of subject's ratings. (HTH)