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Classical conditioning relies on an unconditional stimulus (for example, salivating at the sight of food) – a stimulus that gets a uniform and invariable response. The new response (for example salivating to the sound of a bell)is then tied to this by making the new stimulus occur repeatedly and together with the unconditional stimulus. Then the new response occurs without the need for the unconditional stimulus.
Operant conditioning does not need an unconditional stimulus. It relies on reward (or punishment) of the behavior we want to occur by repeatedly rewarding or punishing when the desired behaviour occurs.
Operant conditioning is usually better because it is difficult to control or manipulate an unconditional stimulus, but is easier to reward or punish the required behavior when it occurs. For instance a child can be stopped from bed-wetting or by crying when the light is turned off by giving a reward but it would be difficult to use classical conditioning method.
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