## 6 Discussion  
Eye tracking identifies the regions of pre-attentive focus on a visual scene in a semi-quantitative manner. It is ideally suited for side-by-side comparisons of different structures, and for estimating their relative coherence. In addition, eye tracking can also give us a good idea of human reactions to single structures, provided the tests are pre-formed in a well-prepared and careful manner. Here is a list of the main findings from the analysis of the images. Figure 16: The building of the Tyrolean Chamber of Commerce and Industry in Innsbruck, Austria, built in the 1900s, in a tightly cropped image (**A**), with its eye-tracking simulation heatmap (**C**). The same image after a frame has been added (**B**) provides a more accurate eye-tracking simulation heatmap (**D**). A high degree of organized complexity, defined through nested symmetries, engages the viewer in pre-attentive, unconscious interest. * Visual engagement distributes uniformly throughout a complex, highly ordered composition, with no gaps and few hotspots in the heatmap. * Hotspots in a successful composition's heatmap coincide with points of functional interest such as the main entry, or prominent windows and other central features. * An unsuccessful (disengaging) composition will show hotspots in irrelevant places such as the building's corner or edge, or away from the building altogether. * The way that engagement depends upon the distance of approach is correlated to organized complexity. The most successful examples show fractal scaling, i.e., organized complexity at every magnification, and thus retain engagement in a scale-free manner. * Plainness and monotonous repetition fail to engage the viewer, resulting in a heatmap with large empty areas. * A non-trivial structure that lacks fractality results in a fragmented heatmap with gaps, which loses the viewer's attention. * The software used here is sensitive to artifacts that might confuse the architectural results. Our suggestions for circumventing those are discussed in the next section. In all the visuals analyzed in this paper, the presence of organized complexity, with nested hierarchies, draws the computed pre-attentive gaze more and more uniformly (an example is seen in Figure 2). On the other end of the design spectrum, glass-facade buildings with minimal detail are not included at all in the pre-attentive processing stage (glass facade buildings in Figure 1 are such examples). Intermediate situations, where there is some detail but it is based on monotonous repetition, are covered by the heatmap only at specific viewing distances, with the pre-attentive field disintegrating at closer distances, and disappearing altogether at larger distances (Figure 8, for example). Scanning experiments reveal how engagement strongly depends upon distance of approach. Taking this factor into account underlines the neurological need for fractal scaling--i.e., coherent structure at every magnification--and argues why buildings ought to have nested levels of scale. The reason is that no other geometric arrangement can feed the nervous system smoothly as we move toward a structure. Fractal scaling fits how humans move--specifically their ambulation--and how the brain craves to see more details as we get closer in, facilitating our approach to the architecture. An essential requisite for building humane places is that the geometry tells us we are heading in the right direction. We need to see fractal scaling, organized complexity, and repeating symmetries, otherwise the brain slips back into a default vigilant state. But then we do not feel safe in a place and cannot be social, particularly when outside. Figure 9 sheds light on the decades-long debate of how the introduction of stylistic minimalism has affected the human psyche. Not all readers might be aware of the central position this question occupies in academic and professional circles, without ever achieving an evidence-based resolution.