Behaviorists study . learned behaviorb. dreamsc. a person's unconscious mindd. chemical and hormonal changes

a. learned behavior                                      

Explanation:

Behaviorists such as Ivan Pavlov, B. F. Skinner, John Watson, and Edward Thorndike, etc studied the concept of behaviorism or behavioral psychology which is a learning-based theory encompassing the idea that all behaviors are being acquired or learned through conditioning.

Learned behavior: The term learned behavior refers to the phenomenon being developed by organisms through experiences. Learned behaviors include both experiences and innate elements i.e, genetics. In other words, learned behavior is defined as an action or skill developed in an individual through watching or being told to perform a particular task.

In the question above, behaviorists study learned behaviors.

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