In this paper, the theoretical foundations and first empirical study regarding a new instrument measuring reflection in education are presented. The question is if it is possible to obtain reliable and valid data with this instrument and how to improve it.

Reflection is claimed to be an important qualification in many social professions (Moon, 1999). Particularly in the teaching profession the ability and the willingness to continuously and critically reflect one’s own practice is currently claimed to be a key concept promoting sound professional behaviour (e.g. Altrichter & Posch, 2007; Terhart, 2002). Although there is a strong claim to implement strategies of reflection into teacher education there are some problems arising with this postulation:

• There exist different definitions and theoretical approaches of reflection in literature. In consequence of this varying notions for some teachers reflection simply means thinking about something and writing down the experiences, feelings etc. whereas for others it is a well defined practice by using methodical frameworks (e.g. Seyfried, 2006; Korthagen, 2005; Gibbs, 1988; Smyth, 1989).
• In educational research a satisfactory operationalization of the concept of reflection is still missing (Korthagen, 2008, 56f). This makes it difficult for teachers and teacher educators to focus their practice on operationally feasible dimensions of reflection.
• In fact there is no theory-based instrument assessing reflection. Hence teacher educators do not know if teacher-students really increase in their reflective competence if they use practices which are considered as methods to enhance reflection.

On grounds of the theoretical considerations which refer a) to the self awareness in Cartesian rationality (Descartes 1637), b) Deweys (1910, 1933) scientific method of reflection, c) Schön’s (1983, 1987) conception of reflection as artistic, personal and non rational activity, and d) the conception of reflection emanating from constructivist epistemology (e.g. Glasersfeld, 1997; Piaget, 1937) and based on current contributions which try to explain the development of reflectivity by describing different types or levels of reflection (e.g. van Manen 1977, Zeichner and Liston 1987) we suggest several dimensions of reflection which describe more or less pronounced reflective thinking (descriptive statements, interpretations with observer-awareness, interpretations without observer-awareness, interrogative statements, explanative statements with observer-awareness, explanative statements without observer-awareness). Statements with observer-awareness express that the person is conscious of the fact that he or she is the originator of this opinion and that someone else can have different opinions of a situation. Due to the self-awareness expressed in these statements they become intersubjectively verifiable. According to Descartes statements with observer-awareness refer to reflective thinking.

The instrument RIFE consists of six fairly complex pictures (photos) of classroom situations. The teacher students or teachers are asked to write down any consideration they have to each photo consecutively. A content analysis of the resulting text is done according the specific dimensions mentioned above.

The following hypotheses are being tested:

• It is possible to obtain reliable data with the instrument RIFE.
• It is possible to obtain valid data with the instrument RIFE. The instrument discriminates between persons with different competence in reflection.

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