Modelling always shows our limited possibilities of expressing all aspects within a concise picture. The techno-morphologic approach discussed in the previous chapter shows how much technological concepts were used to build psychological models. The memory metaphor and the approach of processing stages is the most prominent example for this techno-morphologic thinking. Such approaches comply with some kind of helplessness in finding a psychologically sound approach for modelling cognition. An integrated model needs to be based on more than take over of technological concepts. On the other hand, approaches that are more psychological have been developed. Examples are the SOAR approaches, ranging from goal state models and notations like the Cognitive Complexity Theory (CCT; Card et al., 1983), the Adaptive Control of Thought (ACT – Anderson, 1983) to the PSI model (Dörner, 1999). Another example, coming from a different angle, is the modelling of physiological aspects based on EEG-Electroencephalogram research (overview in Sommer et al., 1998). These methods have additional aspects to offer that complement the existing approaches to safety. However, they did not find a path into error modelling and safety assessments because they were too far away from the engineering needs of safety assessment. The same holds for the detailed aspects of the work of Rasmussen (1986).