In the course of explain dual systems theory, Kahneman (2011) discusses the Heider study, in which:
you see a large triangle, a small triangle, and a circle moving around a shape that looks like a schematic view of a house with an open door. Viewers see an aggressive large triangle bullying a smaller triangle, a terrified circle, the circle and the small triangle joining forces to defeat the bully.
Viewers perceive the movements of the shapes in causal terms. Kahneman then goes on to say:
The psychology of causality was the basis of my decision to describe psychological processes by metaphors of agency, with little concern for consistency. I sometimes refer to System 1 as an agent with certain traits and preferences, and sometimes as an associative machine that represents reality by a complex pattern of links. The system and the machine are fictions; my reason for using them is that they fit the way we think about causes. Heider’s triangles and circles are not really agents—it is just very easy and natural to think of them that way. It is a matter of mental economy. I assume that you (like me) find it easier to think about the mind if we describe what happens in terms of traits and intentions (the two systems) and sometimes in terms of mechanical regularities (the associative machine). I do not intend to convince you that the systems are real, any more than Heider intended you to believe that the large triangle is really a bully.
I've never been able to understand the distinction he is trying to draw there. In what sense are the two systems 'unreal'?
Kahneman, D. (2011). Thinking, fast and slow. Macmillan.