Network theory has some very unusual applications in everyday life. One specific example comes from the analysis of eye movement through use of an eye tracker. Eye trackers trace the movement of the eye when looking at a picture. When an individual looks at an object, he or she does not look at it in a scenic way; rather the eyes fixate on a point and then move sporadically with saccades focusing on specific aspects. Saccades are quick simultaneous movements of both eyes in the same direction. These points of fixation, when analyzed, form a unique network. In analyzing eye movements, regard each saccade as an edge and each fixation as a node—where nodes cluster, like around the eyes, you’re forming nodes of a high degree of connectivity.

Take for example the analysis of a photograph, when an individual looks at a face, most of their time looking is spent in a triangle between the two eyes and the mouth area. These are the nodes with the highest degree of connectivity and have the greatest power. Further, it can be seen that there are other nodes that do not have as much connectivity but are still well connected are areas such as the hair.

It would be simple to come up with an algorithm using simple graph theory to characterize a saccade. Applications for this are extremely interesting in the field of advertising and a lot of time is spent in analysis of the focus of human eye movement in order to adapt marketing to natural human tendencies.

Source: http://courses.cit.cornell.edu/bionb2220/secure/Slides/L40_2009_slides.pdf