When fading is called the temporary use of prompts (additional cues) to achieve a Stimulusdiskrimination. It is a term from behavioral psychology, especially from the area of operant conditioning . In German, this roughly means gradually disappearing . The aim of fading is to learn to differentiate (discriminate) between different stimuli . This happens through the gradual approach of the stimuli or through the gradual withdrawal of additional distinctive stimuli.
- A teacher asks the student for the English equivalent of the German word "Antwort". If the student does not immediately know the correct answer, the teacher can give a clue (i.e. a prompt) that increases the likelihood that the student will find the answer. For example, the teacher says the first letters of the English word ("ans ...") or gives another hint that serves as a prompt ("The word starts in English as it does in German"). For the next query, the teacher can (ideally) reduce the prompt (e.g. say fewer letters of the correct word). The use of prompts is reduced for each query until the student finally brings up the solution without further hints.
The scientific investigation of this process goes back to Burrhus Frederic Skinner . Based on him, the following experimental set-up was developed by Ellen Reese (1966):
- A pigeon that has already learned to get food by pecking at a disc should be taught to peck only when the word “peck” is projected onto the wall of the cage. When it comes to the word “don't peck”, however, it shouldn't peck. The pigeon learns this from the fact that pecking on the disc only leads to food being given when the stimulus “peck” appears. On the other hand, if she pecks as long as “don't peck” can be seen on the wall of the cage, she will not be fed.
In order to “teach” the difference between the two stimuli, both words are initially designed very differently: “peck” z. B. in large black letters and "don't peck" in small red letters. These additional cues (color, size) make it easier for the pigeon to distinguish between these two words.
This is where fading comes into play. The differences between the two stimuli (“peck” and “don't peck”) are reduced in a series of test runs. The large black letters are approximated to the small red letters and vice versa until both words consist of equally large black letters. The pigeon retains the behavior pattern shown at the beginning (peck when "peck" appears, do not peck when "don't peck" appears) through all changes that are made gradually.
For the naive observer, it could now look as if the pigeons could read the inscription on the disk, as if they “understood” what is written there.
- Ellen P. Reese: The Analysis of Human Operant Behavior. Introduction to General Psychology: A Self-selection Textbook. WM. C. Brown Company Publishers, 1966
- Christoph Bördlein: An introduction to behavior analysis. ( Memento of November 4, 2009 in the Internet Archive ) (PDF)