Exposure to one stimulus can temporarily increase the accessibility of related information in memory. That facilitation is priming. After seeing the word “doctor,” people recognize “nurse” faster than they recognize an unrelated word such as “bread.” The effect can occur without conscious awareness of the first stimulus.

Priming appears in many forms. Semantic priming involves meaning. Perceptual priming involves form or sound. Affective priming involves emotional valence. In each case the first stimulus leaves a residual activation that makes related material easier to process.

The phenomenon supports models of memory as an interconnected network. Activation spreads along associative links. Because the effect is usually brief and can operate outside awareness, it has become a standard tool for probing implicit cognition and automatic associations.

• Facilitation of related mental content
• Often unconscious
• Semantic, perceptual, and affective varieties
• Evidence for spreading activation in memory

Experimental designs carefully control for expectation so that the measured speed advantage can be attributed to the prime rather than to strategic processing.