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 time it took to say the name of the light after it was lit. Further experiments changed the number of each different type of light. Hyman was responsible for determining a linear relation between reaction time and the information transmitted. Law Given n equally probable choices, the average reaction time T required to choose among the choices is approximately: where b is a constant that can be determined empirically by fitting a line to measured data. The logarithm expresses depth of "choice tree" hierarchy – log2 indicates binary search was performed. Addition of 1 to n takes into account the "uncertainty about whether to respond or not, as well as about which response to make." In the case of choices with unequal probabilities, the law can be generalized as: where H is strongly related to the information-theoretic entropy of the decision, defined as where pi refers to the probability of the ith alternative yielding the information-theoretic entropy. Hick's law is similar in form to Fitts's law. Hick's law has a logarithmic form because people subdivide the total collection of choices into categories, eliminating about half of the remaining choices at each step, rather than considering each and every choice one-by-one, which would require linear time. Relation to IQ E. Roth (1964) demonstrated a correlation between IQ and information processing speed, which is the reciprocal of the slope of the function: where n is the number of choices. The time it takes to come to a decision is: proportional to : Stimulus–response compatibility The stimulus–response compatibility is known to also affect the choice reaction time for the Hick–Hyman law. This means that the response should be similar to the stimulus itself (such as turning a steering wheel to turn the wheels of the car). The action the user performs is similar to the response the driver receives from the car. Exceptions Studies suggest that the search for a word within a randomly ordered list—in which the reaction time increases linearly according to the number of items—does not allow for the generalization of the scientific law, considering that, in other conditions, the reaction time may not be linearly associated to the logarithm of the number of