You decide to participate as a subject in a research experiment. You are told by the researcher to: "Look at this apple very carefully and tell me your exact sensations and feelings as you experience them." The researcher in this study probably believes in what school of psychology?

Structuralism.

Explanation:

Structuralism was the first school of thought coined first by Wilhelm Wundt then later further developed by his student Edward Titchener.

According to this school of psychology, the researchers try to observe the inner feelings using introspection method.

Introspection is the process in which inner thought and emotion are examined.

In the given case, the researcher believes in "structuralism" school of psychology as he is trying to understand the feelings and thoughts of students when they see an apple.

So, the correct answer is "structuralism".