Scalar Expectancy Theory

About this episode

This episode discusses Scalar Expectancy Theory, a model of animal timing behavior and its implications for both animals and humans.

...and now for another Human Factors Minute! Scalar Expectancy Theory, or SET, is an important model of animal timing behavior credited to John Gibbon in the late 1900s. The idea of SET is that animals have an internal clock and particular memory and decision-making processes, which explains why their behavior can be temporally controlled using fixed-interval reinforcement. The scalar part of SET comes from how animals compare the current time (held in their working memory) to the expected time (held in their reference memory). When the ratio is small enough, the animal performs the behavior. When the ratio is big enough, the animal stops doing the behavior. This ratio allows for the observation that animal timing accuracy is relative to the size of the interval being timed. Although Gibbon’s theory was intended to apply only to animals, John Wearden claimed that SET could also be applied to humans. However, human behavior has much more variability than animal behavior does, mostly due to our attentional allocation, so this application is somewhat debated. While SET was one of the first models of timing, it is not the only one: there are many alternative models of timing, some…

People in this episode

Host: Human Factors Cast

Topics covered

• Scalar Expectancy Theory
• animal behavior
• timing models
• decision-making
• memory processes

Keywords

• Scalar Expectancy Theory
• timing behavior
• animal timing
• internal clock
• fixed-interval reinforcement
• temporal control
• decision-making processes

More episodes of Human Factors Minute

• HFETAG - Personnel · June 10, 2026 · 2 min
• System Safety Society · May 31, 2026 · 1 min
• Heart Rate Monitoring · May 20, 2026 · 2 min
• The Diffusion Model · May 10, 2026 · 2 min
• HFETAG - Standardization · April 30, 2026 · 1 min
• OSHA Standard 1910 · April 20, 2026 · 1 min