Hick's Law - Background

Background

In 1868, the relationship between having multiple stimuli and the choice reaction time was reported by Franciscus Donders. Later, in 1885, J. Merkel discovered the response time is longer when a stimulus belongs to a large set rather than a smaller set of stimuli. At this point, psychologists began to see similarities between this phenomenon and the Information Theory. Hick first began experimenting with this theory in 1951. His first experiment involved 10 lamps with corresponding Morse Code keys. The lamps would light at random every five seconds. The choice reaction time was recorded with the number of choices ranging from 2–10 lamps. E. Roth (1964) could demonstrate a significant correlation between IQ and information processing speed, which is the reciprocal of the slope of the function

Reaction Time = Movement Time + log₂(n) / Processing Speed

where ProcessingSpeed • log₂(n) is the time taken to come to a decision and n is the number of choices.

Hick performed a second experiment using the same task, while keeping the number of alternatives steady at 10. The participant performed the task the first two times with the instruction to perform the task as accurately as possible. For the last task, the participant was asked to perform the task as quickly as possible.

While Hick was stating that the relationship between reaction time and the number of choices was logarithmic, Hyman wanted to better understand the relationship between the reaction time and the mean number of choices. In Hyman’s experiment he had eight different lights arranged in a 6x6 matrix. Each of these different lights was given a name, so the participant was timed in the amount of time it took to say the name of the light after it was lit. In further experimentation using this model, the number of each different type of light changed. Hyman was responsible for determining a linear relation between reaction time and the information transmitted.