The SIZE PROZESS® Model is based on established psychological principles, combining approaches from depth and humanistic psychology with classical and systemic transactional analysis. It is further enriched by bioenergetics, modern neuroscience, and systemic consulting practices.

Origin and Development
Between 1999 and 2004, Hannes Sieber (Germany) and Fritz Zehetner (Austria) jointly developed the foundational model. The name SIZE derives from the initials of their surnames: SI (Sieber) and ZE (Zehetner).

Since 2004, Fritz Zehetner has independently advanced the model, continuously enhancing it, particularly with a focus on systemic approaches.

Zehetner translates complex psychological theories into clear, practical models. His goal is to promote individual strengths and potentials by focusing on psychological needs and their interactions with social and organizational contexts.

Moving Away from Rigid Typologies to Systemic Thinking
With his SIZE PROZESS® Model, Zehetner breaks away from traditional typologies and views personality as a dynamic interplay of six personality styles. These styles interact flexibly with their environment and adapt to different life situations and contexts. Rather than categorizing people into fixed types, the model offers a practical, individualized perspective on personality and development.

Practical Orientation and Integrative Approach
The SIZE PROZESS® Model integrates:

• Classical and systemic transactional analysis
• Systemic concepts
• Modern neuroscience

It provides a versatile tool for fostering self-reflection and personal growth. Zehetner emphasizes simple, clear formats that distill complex concepts to their essence.

The SIZE PROZESS® Model is more than just an analytical tool—it is an innovative developmental approach that helps unlock individual potential and enhances communication and collaboration within teams and organizations.