"In 1877, Charles Darwin, the biologist who later put forward the theory of evolution, was doing the first scientific infant-observation study, observing and writing about his son's behaviours and emotions in descriptive psychological terms." (Open U.)
Darwin was objectively describing and writing down what he was observing about the behaviour of his son; he was annotating all he could observe about one specific behavior, duration, hour, what had happened before, what happened later, all possible information relating one specific event, that`s a scientific infant-observation study.
"Wilhelm Wundt methods included use of the scientific experimental method, introspection (asking people to think about and report on their inner feelings and experiences), and ethnography (observations of human culture)." (Open U.)
Introspection proved not to be a very reliable method for making researchs, so today is just part of the history in the evolution of the Psychological science. But at least Wundt was objectively writing down everything that was reported to him, it meant an effort.
"William James, an American professor trained in philosophy, medicine and physiology, who published the influential Principles of Psychology in 1890, also advocated a multi-method approach that included introspection and observation." (Open U.)
"Sigmund Freud, the first psychoanalyst, was a medical doctor and research physiologist who opened his psychology consulting room in Vienna in 1886. Freud, working at the same time as Wundt and James, pioneered a method that involved listening closely to people's personal accounts of their symptoms, emotions, and their lives more generally, asking insightful questions and attending to the particulars of language use and unconscious phenomena." (Open U.)
Sigmund Freud wrote many interesting books, created Psychoanalysis, a kind of therapy still used nowadays by trained therapists, and had a great deal of new ideas; some of them have evolved with further researchs, others have lost credibility.