Abstract
Two experiments were conducted to investigate the effects of key-arrangements on a keyboard upon key-punching operations. Ten-by-ten matrices in which each one hundred of numerals from zero to ninety-nine were arranged were used as the experimental materials. Detection times of the given figures in the matrices were measured as the function of the numeral arrangements which were varied in a systematic way. The matrix was partitioned into some parts, in which the assigned numerals were arranged randomly while the assignments of numerals were in order or at random according to the experimental design. By varying the numerals of partitions the orderliness of arrangements were changed systematicaly. It is shown that figure detection time has some systematic relations with the orderliness of arrangements and that numbers of elements near and below ten in each part may be critical numbers in such a type of detection task so that detecting behavior undergoes qualitative changes over such critical numbers.
