The Indonesian archipelago, which covers an area of close to 2 million km² , stretches from West to East over more than 5000 km and from North to South over approximately 1800 km. It is inhabited by about 500 different ethnic groups most of which have their own language. Bahasa Indonesia is the national language officially designed for inter-ethnic communication since 1945 (Grimes C. 1996). However, speakers of regional and local languages often have a limited mastery of Indonesian. For purposes of development communication, the gap of communication resulting from this is widened by the general lack of adequate terminology in regional and local languages which constitutes a major obstacle to their use for conveying innovative concepts, resulting in a loss of communicative sustainability and hence of sustainability of development per se, since without adequate indigenization of the innovative message its appropriation by local actors is in jeopardy.

In addition, language choice has deep social implications and hence an incidence on acceptability of messages, Indonesian being the only medium deemed appropriate for formal deliberation and decision-making except at the most local level. The barrier to the unimpeded flow of information - both top-down and bottom-up - is further heightened by the internal variation of Indonesian, its still incomplete standardization, and the interferences from local languages in its regional varieties. As a consequence, immediate communication is often not possible between project administrators and local actors even if both supposedly speak some variety of Indonesian. Bilingual intermediaries must be called in in order to bridge the communication gap "artificially", creating a further obstacle to spontaneous interaction desirable for goal-directed empathy and successful negotiation of problematic issues.

Verbal and non-verbal aspects of communication are of equal importance and interact in significant ways in Indonesian society. Public debate and private conversation are equally subject to the laws of a strictly hierarchical social order, known as adat (customs and tradition). Bapakisme (fatherhood) restricts speaking privileges to prominent members of the society while imposing strong limitations on less prominent ones, largely excluding women and those being insufficiently competent in Bahasa Indonesia. Another "century old" and "highly developed aspect" of adat which affects decision-making and communication of decisions is the use of the "right channel" or "filter" (Draine and Hall 1986). Consequently, the group of people entitled to be legitimately addressed in conveying innovative messages is limited at the outset and virtually excludes e.g. all those having a less than perfect command of Indonesian, i.e. the vast majority of the target population of development projects.