There has been a dramatic growth in interactive technology use by children under the age of 5 during the past decade. Despite this growth, children under the age of 5 typically participate only as users or testers in the design process in the overwhelming majority of projects targeting this population presented in key child-computer interaction venues. In this paper we introduce play-based design, an age-appropriate design method to give 3-4-year-old children a voice in the design process. More specifically, we contribute a thorough analysis of the use of existing methods to design technologies for children under the age of 5, a summary of the process that resulted in the development of play-based design, a detailed description of play-based design, a qualitative analysis of our experience implementing play-based design with two groups of children, and a discussion of play-based design's place among other methods, its advantages, and limitations.

While the design of Voice User Interfaces (VUIs) has mostly focused on applications for adults, VUIs also provide potential advantages for young children in enabling concurrent interactions with the physical and social world. Current applications for young children focus mostly on media playing, answering questions, and highly-structured activities. There is an opportunity to go beyond these applications by using VUIs to support less structured, developmentally appropriate activities. In this paper, we describe our first step in pursuing this opportunity through an exploration of voice agents to facilitate high-quality social play guided by a partnership with eight 3-4 year old children. During 24 design sessions, we explored making voice agents tangible and enabling children to control what voice agents say. After analyzing the sessions, we learned voice agents could help keep children socially engaged in play and children liked incorporating the agents with the physical aspects of their play. On the other hand, enabling children to control the voice agents caused distractions from play.