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What Is an Unconditioned Stimulus?



In classical conditioning, the unconditioned stimulus (US) is one that unconditionally, naturally, and automatically triggers a response. For example, when you smell one of your favorite foods, you may immediately feel very hungry. In this example, the smell of the food is the unconditioned stimulus.

In Ivan Pavlov's classic experiment with dogs, the smell of food was the unconditioned stimulus. The dogs in his experiment would smell the food, and then naturally begin to salivate in response. This response requires no learning, it simply happens automatically.

Some more examples of the unconditioned stimulus include:

  • A feather tickling your nose causes you to sneeze. The feather tickling your nose is the unconditioned stimulus.

  • Pollen from grass and flowers causes you to sneeze. The pollen from the grass and flowers is the unconditioned stimulus.

In each of these examples, the US naturally triggers an unconditioned response. You don't have to learn to respond to the US.

Related Terms:

More Psychology Definitions: The Psychology Dictionary

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