In the Little Albert study, the unconditioned stimulus was:

1. The unconditioned stimulus is the one that produces a reflex with no learning. 2. Albert showed a reflexive fear of sudden loud noises, so the loud sound made by striking a hammer against a metal bar is the unconditioned stimulus. 3. Albert initially played happily with the white rat, proving the rat began as a neutral stimulus; after pairing it became the conditioned stimulus. 4. Crying is the response, not a stimulus, and the Santa Claus mask illustrates later generalization. 5. Mislabelling the rat as the unconditioned stimulus is the classic error here. _Source: OpenStax Psychology (1st ed., CC BY 4.0), Ch 6 "Learning", §6.2 Classical Conditioning_