[en] An experiment was performed during 1983 that measured performance of nuclear plant operators with and without a computer-based operator aid. This report discusses the results of that experiment and their implications for design and regulation of advanced computer aids in nuclear control rooms. The aid tested is called a response tree and is intended to help operators properly align a piping system despite component or support system failures. In the experiment, 28 reactor operator subjects were required to align a system to inject coolant and stop a temperature excursion in a simulated reactor. The experiment did not show an improvement in operator performance when the response tree aid was used. More important, the experiment did produce several conclusions related to the design and evaluation of computer aids in nuclear control rooms