Scientists are by nature interested in new fancy machines that can reveal clues about the nature of the mind and brain. In general, the machines of today are more sophisticated than those of decades ago, leading to the view that newer is better. But such is not the case regarding data: Some old data from psychological experiments can be more informative than newer data, depending on how the data were collected and the nature of the data.
Data are deemed good or bad, not because of when they were obtained, but because of how they were obtained. If the data were obtained using sound scientific methods, then the data will always be informative and should always be consulted. Scientifically speaking, 'data age' is not a predictor of 'data quality.' It is for this reason that, in order to fully understand the nature of a given psychological phenomenon--be it about memory, perception, or abnormal behavior--one must first peruse all of the data, including those contained in the old dusty books, often neglected books whose names form the bibliographies of history texts. After this is done, the investigator can then decide which data to focus on further. Neglecting findings because of their age leads to experimenters doing experiments that had already been done, which makes science advance more slowly. Thus, from this point of view, 'knowing the history of psychology and neuroscience' equals 'knowing all the data of psychology and neuroscience.' Every new experiment contributes to this corpus of data, findings, facts, and hypotheses.