Is self-knowledgeability a most critical concept in stated preference research?

Stated preference techniques are increasingly used in the prediction of behaviour in transport and communications research. The uses and applications of such techniques are considered. The concept of self-knowledgeability is introduced as an individual's specific ability to give answers with behaviour-predicting potential. It is suggested that problems related to the concept of self-knowledgeability are in essence recognized but in practice overlooked. Conceptual, research and object models are introduced and an integrated model showing the relationship between the concept, object and researcher is presented.