Rescorla–Wagner model
The Rescorla -Wagner model is a mathematical model to make the classical conditioning, and some of its main effects predictable. The basic assumption of the model states that a stimulus can only serve as a good predictor for predicting effects if it is surprising. It was presented in 1972 by Robert A. Rescorla and Allan R. Wagner and even today has its permanent place in the psychology of learning - although it has been amended and expanded since then.
Basics
In classical conditioning, an organism ( subject or experimental animal ) repeatedly unconditioned stimulus ( U.S.) and a conditioned stimulus ( CS) are presented together. The subject, previously only showed a reaction to the U.S. ( unconditioned response, UR ), after a few repetitions shows a similar response ( conditioned response, CR ) even when the presentation of the conditioned stimulus alone.
In classical conditioning, a distinction acquisition and Extinktionsdurchgänge:
- Acquisition (acquisition ). Unconditioned stimulus and conditioned stimulus are presented together. The probability of the organism to the conditioned stimulus is a Conditioned response increases with each pass - and at the beginning very strong and later less and less.
- Absorbance ( extinction ). The conditioned stimulus is presented alone. The probability of the organism to the conditioned stimulus is a conditioned response decreases with each pass, until finally no conditioned response to the conditioned stimulus is shown.
The importance of the Rescorla -Wagner model
Prior to the Rescorla -Wagner model has been repeatedly tried in vain to devise a mathematical model that predicts the probability of an organism to the conditioned stimulus is the conditioned response. Although all were able to explain the basic form of classical conditioning, but failed due to the declaration of conditioning with more than two stimuli or predicting special effects. The Rescorla -Wagner model was not only the first which could explain all the previously known effects mathematically, it could also predict new effects.
The model predicts not only the ordinary classical conditioning with one or more conditioned stimuli correctly ahead, but makes particular the following effects predictable:
- Extinction
- Blocking
- Conditioned inhibition
The problem for the model are phenomena such as latent inhibition, configural cues (including configuration learning), spontaneous recovery and associative bias.
The formula
The Rescorla -Wagner model culminates in the mathematical equation:
The individual variables have the following meanings and value ranges:
- A is the conditioned stimulus ( CS), or one of the conditioned stimuli, if there are several. A can be replaced with more words; For example, you could write for a particular application of the formula: .
- N is the number of the conditioning passages. Including the zero - - Thus every natural number n any size can be.
- V is the association strength is the strength of the associative link between a conditioned stimulus ( CS) and the unconditioned stimulus ( U.S.). V is a mathematical probability and takes a real value between 0 and 1. Thus: the associative strength of the conditioned stimulus A,
- The change in the associative strength of stimulus A and
- Changing the association strength of the stimulus A, between the n-th and the (n 1) th passage.
In simple terms, the change in the strength of association depends on the difference between the maximum possible strength of association and current strength of association:
Thus, for example, observe that initially, when this difference is still big, big learning progress to be made, while only small learning progress can be made later if the performance is already close to perfection.