unique personality into larger institutional structures.'" Inspired by the horrific events of Nazi Germany, Milgram's obedience experiments have been used to explain a range of social influences on the individual—including how police interrogators can get innocent people to confess to crimes they did not commit. At the same time, these experiments have come under attack. Some critics questioned whether subjects sensed the unreality of the situation. Others questioned the relevance of the laboratory setting to the real world. The most devastating criticisms involved the ethics of the basic experimental design. Professor Milgram, for his part, felt that such misgivings were traceable to the unsavory nature of his results: "Underlying the criticism of the experiment," Milgram wrote, "is an alternative model of human nature, one holding that when confronted with a choice between hurting others and complying with authority, normal people reject authority." Daniel Raver looks back:Even though Milgram's personal interests were diverse, his greatest contribution to psychology came through one set of experiments, but in that set he contributed monumentally. He helped justify a science some dismiss as unimportant, contributed to the understanding of humanity, and, even if by way of attacks against him, contributed to the consideration of the treatment of research participants. Small-world phenomenon The six degrees of separation concept was examined in Milgram's 1967 "small-world experiment", which tracked chains of acquaintances in the United States. In the experiment, Milgram sent several packages to 160 random people living in Omaha, Nebraska, asking them to forward the package to a friend or acquaintance who they thought would bring the package closer to a set final individual, a stockbroker from Boston, Massachusetts. Each "starter" received instructions to mail a folder via the U.S. Post Office to a recipient, but with some rules. Starters could only mail the folder to someone they actually knew personally on a first-name basis. When doing so, each starter instructed their recipient to mail the folder ahead to one of the latter's first-name acquaintances with the same instructions, with the hope that their acquaintance might by some chance know the target recipient. Given that starters knew only the target recipient's name and address, they had a seemingly impossible task. Milgram monitored the progress of each chain via returned "tracer" postcards, which allowed him to track the progression of each letter. Surprisingly, he found that the very first folder reached the target in just four days and