The purpose of this study is to deepen our understanding of communication by proposing a related, novel construct: intra-action. We define intra-action as communication with oneself through the use of external tools. In intra-action, similarly to communication involving distinct parties, learners use discourse conducted with support from communication technology to deepen their understanding of the subject matter. Unlike in conventional communication in which the discourse is targeted at others, in intra-action the discourse is targeted at the learners themselves. Examples of intra-action activities and tools are digital annotation, electronic diaries and blogs. We study its impact on learning outcomes and its relationships with other kinds of communication: interaction (substantive communication with others) and outeraction (rapport-building communication with others). Three tools: annotation, discussion board and instant messenger were designed to support intra-action, interaction and outeraction, respectively. After our experiment, the results clearly demonstrate that intra-action has stronger relationship with learning outcomes than interaction or outeraction. Also, considerable correlation was detected between intra-action and interaction. Subsequent interviews with learners indicated that considerable part of the positive relationship between intra-action and learning achievement may be due to cause-effect, namely, intra-action activities are perceived by learners as contributing to positive learning outcomes.