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Goal items were selected by a series of touch-menu choices among sequentially subdivided ranges of integers or alphabetically ordered words. The number of alternatives at each step, b, was varied, and, inversely, the size of the target area for the touch. Mean response time for each screen was well described by T = k+clogb, in agreement with the Hick-Hyman and Fitts' laws for decision and movement components in series. It is shown that this function favors breadth over depth in menus, whereas others might not. Speculations are offered as to when various functions could be expected.
Landauer et al. (Tue,) studied this question.