Reliability and validity of coding systems for bodily forms of communication

This contribution aims to provide an up-to-date picture of the state of the art on reliability and validity in the field of quantitative observation of verbal and nonverbal processes of communication, where the main source of error is the human observer who codes the interactants behaviour by means of coding schemes. After a lexical clarification that allows readers a more aware orientation in this field, the contribution a) introduces the basic concepts of intra-, inter- and observer reliability; b) reviews the summary and point-by-point agreement coefficients among which the most used Cohen’s K; c) critically reviews the K at the light of the more recent advances; d) provides brief hints on validity of coding systems. Research examples, applications, indication for the right use of a determined coefficient accompanies the contribution.