Final answer:
Behavior analysis operates on the assumption that behavior can be understood through observation and measurement and is influenced by external factors like the environment. It uses controlled experiments and observational studies to gather data, thereby establishing it as a scientific field.
Step-by-step explanation:
The field of behavior analysis is grounded in several philosophical assumptions. One key assumption is that behavior can be understood through observation and measurement. This supports the idea that behaviorism focuses on observable behaviors rather than internal mental states. Contrary to some of the options provided in your question, behavior analysis firmly holds that behavior is indeed influenced by external factors, specifically the environment and its consequences on the organism, an idea championed by B.F. Skinner and other behaviorists. This view suggests that learning and behavior are primarily shaped through interactions with the environment, negating the assumption that behavior is solely determined by individual choices without external influence.
Behavior analysis is considered a scientific field because it employs empirical methods, such as controlled experiments and observational studies, to form hypotheses and draw conclusions about human behavior. The approach heavily relies on data driven from experimental or observational work to explain behavior, as well as the cognitive and biological processes underlying it. Finally, it's important to recognize that behaviorist perspectives do not constitute the entirety of psychological science but rather serve as one of several approaches to understanding behavior.