Chapter 2

Chapter 2 introduces the basics of simulating health behavior using a simple model of how collective tolerance can emerge from individual intolerance. First we model a simple interaction at the bacterial level, including bactericide and bacterial resistance. Then we add a third strain of bacteria, finding the rock-paper-scissors game model well captures the emergent tolerance for all three strains. Variations on this model, such as adding in effects of human antibiotic taking behavior extend the potential usefulness, but without disrupting the basic emergent tolerance. In fact, one variation on this simple model sees both the thriving of altruistic bacteria in this condition of cyclic tolerance. We examine variations such as having bacteria pay a cost for resistance, or for producing bacteriocide, and a benefit for succeeding in acquiring resources. In all these variants we see emergence of collective tolerance. We show how we can code the essence of the model dynamics in three simple IF-THEN statements, one for each bacterial strain killing another strain, but still showing emergence of tolerance for diversity sustained through cyclic balance, despite the individual intolerance of each individual strain. Then we examine a simple model of the opposite, neighborhood segregation, showing how collective intolerance emerges even when individuals are very tolerant.