es psychology unique and different from other fields of sciences, especially from the natural sciences, such as math, physics, biology, and chemistry?...

What do you think makes psychology unique and different from other fields of sciences, especially from the natural sciences, such as math, physics, biology, and chemistry? What are the possible 'obstacles' or challenges unique to psychological research (i.e., obstacles that only psychologists have to deal with when conducting research), and how do you think psychologists can overcome those obstacles?