What is Hick's law in simple terms?

The more options you have to choose from, the longer a decision takes, but the increase is gradual: each doubling of options adds roughly a fixed amount of time.

Does Hick's law always hold?

No. With extensive practice, or when stimuli and responses correspond very naturally, the increase in reaction time with more options can shrink greatly or disappear.

Hick's Law

🧠 Psychology By CampusDown Wiki Editorial Team Last updated October 27, 2026

Hick's law, also called the Hick–Hyman law, is a principle established experimentally by the British psychologist William Edmund Hick (1952) and the American psychologist Ray Hyman (1953): with n equally likely alternatives, choice reaction time increases in proportion to log₂(n+1). More generally, reaction time is a linear function of the information conveyed by the stimulus rather than of the number of alternatives as such.

Contents

1. Discovery and formula
2. The information-processing view and related laws
3. Exceptions and cognitive models
4. FAQ
5. References

Discovery and formula

Merkel (1885) had already observed in the nineteenth century that reaction time lengthens as alternatives increase, but by ever smaller amounts. Hick (1952) applied Shannon's (1948) information theory to formalize the relation as RT = b·log₂(n+1), where the +1 reflects uncertainty about whether a stimulus will appear at all. Hyman (1953) held the number of alternatives constant while varying stimulus probabilities and sequential dependencies, showing that reaction time is linearly proportional to the average information transmitted in bits, not to the number of alternatives. These results established the view of the human operator as an information channel of limited capacity.

Together with Fitts's (1954) law, which expressed the difficulty of movements as information, Hick's law is a leading example of explaining human performance through information theory. Both laws share the form of processing time increasing logarithmically with information, and both invite comparison with the Weber–Fechner law of sensory magnitude. Teichner and Krebs (1974) synthesized research on visual choice reaction time, showing that the slope of the law varies with stimulus and task conditions. Jensen (1987) reviewed research in the Hick paradigm linking individual differences in reaction time slopes to intelligence test scores.

Exceptions and cognitive models

Mowbray and Rhoades (1959) showed that after extensive practice the rise in reaction time with the number of alternatives can almost disappear, and Leonard (1959) reported that with very high stimulus–response compatibility, as when fingers respond to vibrations applied to them, the slope becomes flat. Longstreth, El-Zahhar and Alcorn (1985) also explored exceptions to the law. Theoretically, models in which evidence for several alternatives accumulates competitively, such as the leaky competing accumulator of Usher and McClelland (2001), reproduce the logarithmic relation, while Schneider and Anderson (2011) proposed a memory-retrieval model. Proctor and Schneider (2018) reviewed more than six decades of research on Hick's law.

FAQ

What is Hick's law in simple terms?: The more options you have to choose from, the longer a decision takes, but the increase is gradual: each doubling of options adds roughly a fixed amount of time.
Does Hick's law always hold?: No. With extensive practice, or when stimuli and responses correspond very naturally, the increase in reaction time with more options can shrink greatly or disappear.

Sources reviewed: 2026-10-26

References

Hick, W. E. (1952). On the rate of gain of information. Quarterly Journal of Experimental Psychology, 4(1), 11–26.
Hyman, R. (1953). Stimulus information as a determinant of reaction time. Journal of Experimental Psychology, 45(3), 188–196.
Merkel, J. (1885). Die zeitlichen Verhältnisse der Willensthätigkeit. Philosophische Studien, 2, 73–127.
Shannon, C. E. (1948). A mathematical theory of communication. Bell System Technical Journal, 27(3), 379–423.
Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6), 381–391.
Mowbray, G. H., & Rhoades, M. V. (1959). On the reduction of choice reaction times with practice. Quarterly Journal of Experimental Psychology, 11(1), 16–23.
Leonard, J. A. (1959). Tactual choice reactions: I. Quarterly Journal of Experimental Psychology, 11(2), 76–83.
Teichner, W. H., & Krebs, M. J. (1974). Laws of visual choice reaction time. Psychological Review, 81(1), 75–98.
Jensen, A. R. (1987). Individual differences in the Hick paradigm. In P. A. Vernon (Ed.), Speed of Information-Processing and Intelligence (pp. 101–175). Norwood, NJ: Ablex.
Usher, M., & McClelland, J. L. (2001). The time course of perceptual choice: The leaky, competing accumulator model. Psychological Review, 108(3), 550–592.
Schneider, D. W., & Anderson, J. R. (2011). A memory-based model of Hick's law. Cognitive Psychology, 62(3), 193–222.
Proctor, R. W., & Schneider, D. W. (2018). Hick's law for choice reaction time: A review. Quarterly Journal of Experimental Psychology, 71(6), 1281–1299.
Longstreth, L. E., El-Zahhar, N., & Alcorn, M. B. (1985). Exceptions to Hick's law: Explorations with a response duration measure. Journal of Experimental Psychology: General, 114(4), 417–434.

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This article was last updated on October 27, 2026. It is based on widely recognized original works and textbooks; when citing it in a paper, please check the original sources listed in the references.