Final answer:
Freud's psychoanalytic theory was influenced by his clinical observations, including treatment efforts, slips of the tongue, and patient work, but not significantly by experimental research. His approach to understanding the unconscious mind through case studies marked the development of key psychological concepts despite the contentious nature of some of his theories.
Step-by-step explanation:
The question asks which factor did NOT have a significant influence on the development of Freud's theory. Reviewing what influenced Freud's development of psychoanalytic theory indicates that his efforts to treat mental disorders (a), observation of slips of the tongue (c), and knowledge gained from working with patients (d) all played a crucial role. However, the results of his experimental research (b) had the least impact as Freud is known for developing his theories primarily through clinical observations and case studies rather than through the scientific experimental method.
Freud's psychoanalytic theory posited the existence of the unconscious mind and he utilized techniques like dream analysis and the talking cure to explore it. While modern research does not support all of Freud's ideas, the importance he placed on early childhood experiences, unconscious processes, and personality development remain significant. Notably, his methods laid the groundwork for various psychoanalytic concepts and have had a lasting impact on the field of psychology, even though several of his specific theories have been disputed or refined over time.