The main emphasis placed in chapter two is why research methods are so critical to science. As humans we have many tendencies such as being biased towards a certain view and heuristics which are mental shortcuts. One of the more interesting type is a hindsight bias where us as humans seem to think that we should have known the answer before the fact, once we already know the aftermath of the event. This is one of many varying reasons why experiments and good research design is necessary. There are a wide array of tests used to manipulate human bias such as a Naturalistic Observation, observing real-word situations without knowing the ongoing experiment. Other common experiments used are case studies, correlational designs and controls groups, which are more used as more planned and usually already expect certain results. Validity is the main limiting factor in all of these because when people answer untruthfully it creates illegitimate results.
The thing I found interesting between all the different studies is the ethical aspect to them. The line between pain and suffering in human studies versus animal studies is very different. In the early 1900's there was a test known as Tuskegee where humans had syphilis and were to not be treated simply to see what the results would be. The morality of this shocked me and made me question other human studies that have caused pain. Now instead of humans, they often do studies on small animals, which in the eyes of many are almost just as bad.