In this chapter, Lieberman discusses the evolutionary reasons behind our reasoning in cost benefit analyses. We willingly engage in potentially harmful behaviors because they have benefits short term, but may have consequences in the long term. Examples of this include smoking, tanning booths, and pollution. Lieberman suggests that this behavior occurs because we fail to see the novelty of our situation. For us, it is normal to live the way we do, and therefore, we overlook potentially dangerous behaviors. Lieberman suggests that a second factor is that humans believe that if something is comfortable it must be good for us. One example of this is the belief that wearing comfortable shoes is necessary, when in fact, shoes are a very recent development in our history. Lieberman argues that shoes help prevent injury from running with bad form, but even with shoes running long distances in this manner will result in injury. When running barefoot, humans are unable to run with bad form, because it will hurt. Lieberman argues that both are good options, but that barefoot running will not allow for bad form. However, one shoe related injury, called plantar fasciitis, which occurs when the muscles of the foot arch become weak. Doctors usually treat the symptoms, which includes shoes with arch support, which relieve the symptoms but only increases the problem of weak arch muscles. Lieberman argues that when a person suffers from a repetitive stress injury, the cause should to treated instead of just relieving the symptoms. Lieberman argues that myopia, or nearsightedness is another mismatch disease. In fast, evidence shows that only 3% of hunter gatherers are nearsighted, and that only the upper class in early European society suffered from nearsightedness. It’s been theorized that if a child persistently stares at close objects, it will lengthen the eyeball’s walls, causing myopia. However, this hypothesis is controversial, and has only been tested in animals. Another hypothesis is that the invention of glasses has allowed for the selection of bigger brains, which causes myopia. But Lieberman is quick to discredit this theory, stating that brain size has actually decreased since the Ice Age. Either way, someone can be predisposed for myopia, but it is the environmental factors that cause myopia.