Pet rocks. Silly Bandz. Planking. A fad is a temporary and widely adopted behavior or interest that spreads quickly and fades just as fast. It differs from a fashion, which has longer staying power, and from a custom, which is deeply rooted. Fads are often trivial, but they reveal how ideas and products move through populations.

Sociologists study fads to understand diffusion and collective behavior. Fads spread through networks, especially among adolescents and young adults. Social media accelerates the cycle. A dance challenge can go global in days and disappear in weeks.

Common types

• Objects: toys, gadgets, clothing items
• Activities: dance moves, diets, challenges
• Phrases: slang, catchphrases, memes
• Beliefs: briefly popular theories or panics

Not all fads are harmless. Some promote dangerous behavior, like the Tide Pod challenge. Others, like the Ice Bucket Challenge, raise money for causes. The line between fad and social movement can blur when a trend gains lasting organizational form.