The success of natural sciences had a significant influence on the emergence of psychology particularly because the scientific methods used by sciences such as biology and chemistry were regarded as the only reliable methods for discovering reliable knowledge about the world.
Therefore, in order to be accepted and to flourish as a subject in its own right, psychology had to adopt the methods of the natural sciences.
The first ever lab dedicated to psychological reasearch was opened by Wilhelm Wundt in Germany 1879.
His objective was to document the nature of human consciousness and this method came to be known as introspection.
Introspection - The process by which a person gains knowledge about his or her own mental and emotional states as a result of the examination or observation of their conscious thoughts and feelings.
The methods used to investigate the mind would be recognised as scientific as all introspections were recorded under strictly controlled conditions.
The same standardised intructions were given to each participant and therefore the procedures could be replicated.
The behaviourist John B. Watson's main problem with introspection was that it produced data that was subjective and varied from person to person. This made it difficult to establish general principles.
Watson was also highly critical of introspections focus on private mental processes and proposed that a truly scientific psychology should restict itself to only studying phenonema that could be observed and measured.
Therefore from this the behavourist approach was born and with it the emergence of psychology as a science.
Watson and later Skinner brought the language, rigour and methods of the natural sciences into psychology.
Many modern psychologists still rely on the experimental method as part of their research and practices.