The Human as a Constrained Optinal Editor

A model of human performance on intraline text editing, the modification of a line of text, is presented. This model is based on an optimal minimum keystroke solution to the text modification plus a description of those keystrokes that are not easily predicted: feedback, command selection idiosyncrasies, and errors. To better match the human, who is assumed to employ an optimal sequence of editing commands, the optimal solution-was constrained to use the same types of command each human had been observed to use. The model´s constraints and descriptions of keystrokes both give rise to an increased understanding of text editing and recommendations for editor design improvements.