[3][4] Because he was a student of Wilhelm Wundt at the University of Leipzig, Titchener's ideas on how the mind worked were heavily influenced by Wundt's theory of voluntarism and his ideas of association and apperception (the passive and active combinations of elements of consciousness respectively).
Introspection literally means 'looking within', to try to describe a person's memory, perceptions, cognitive processes, and/or motivations.
[9] Structuralists believe that our consciousness is composed of individual parts which contribute to overall structure and function of the mind.
These elements could be broken down into their respective properties, which he determined were quality, intensity, duration, clearness, and extensity.
[10] The second issue in Titchener's theory of structuralism was the question of how the mental elements combined and interacted with each other to form conscious experience.
Wundt believes this type of introspection to be acceptable since it uses laboratory instruments to vary conditions and make results of internal perceptions more precise.
In fact, Wundt's main theory was that of psychological voluntarism (psychologischer Voluntarismus), the doctrine that the power of the will organizes the mind's content into higher-level thought processes.
The main critique of structuralism was its focus on introspection as the method by which to gain an understanding of conscious experience.
Behaviorists, specifically methodological behaviorists, fully rejected even the idea of the conscious experience as a worthy topic in psychology, since they believed that the subject matter of scientific psychology should be strictly operationalized in an objective and measurable way.
However, radical behaviorism includes thinking, feeling, and private events in its theory and analysis of psychology.
Structuralism also believes that the mind could be dissected into its individual parts, which then formed conscious experience.
This also received criticism from the Gestalt school of psychology, which argues that the mind cannot be broken down into individual elements.
[14] James in his theory included introspection (i.e., the psychologist's study of his own states of mind), but also included things like analysis (i.e., the logical criticism of precursor and contemporary views of the mind), experiment (e.g., in hypnosis or neurology), and comparison (i.e., the use of statistical means to distinguish norms from anomalies) which gave it somewhat of an edge.
[14] Researchers are still working to offer objective experimental approaches to measuring conscious experience, in particular within the field of cognitive psychology, which is in some ways carrying on the torch of Titchener's ideas.