Robert is an instructor in a music academy. he thinks john, a new student, lacks confidence to perform on stage. therefore, he seldom lets john play on the stage and chooses other students over john. this results in john developing stage fright and losing confidence in his ability to perform on stage. this is an example of

Self-fulfilling prophecy

Explanation:

Self-fulfilling prophecy's about the false perception leads to confirmation. This has happened in many cultures and arts. Many psychologists and researchers found that our beliefs will affect our outcomes.

It happened particularly when we are manifested with our expectations. The placebo effect is the most famous example of a self-fulfilling prophecy. It is an important concept but also used in sociology as well. It was proposed by Robert Merton.  

Thus here John is in self fulfilling stage where he develops fright and losing confidence in his ability

answer; control group;

i believe the answer is: description

description refers to the goal of psychologist to identify the phenomenon that being observed. this goal is being actualized by collecting data/information from various clues that observed through the phenomenon. this goal must be accomplished before pyschologist able to create methods of treatment.