Brown & Archer, 1956) have studied the effect of variations in the amount of nonredundant irrelevant information on concept identification. In general, a linear degradation of performance is produced by an increase in irrelevant information.Two additional studies (Walker, 1957;Wargo, 1960) have investigated the concurrent effect of variation of nonredundant relevant information. In both of these studies, task difficulty increased as a function of an increase in relevant and irrelevant information. However, Walker found the increase to be nonlinear and also observed a significant interaction between the two variables. The failure of Wargo to find either of these effects was assumed to be due to certain metholological differences which will be considered later.Except for a study by Lordahl (1959), all of the previous concept identification studies have used visual stimuli only. In the exception, Lordahl presented problems which required 5 to use 1 bit of relevant visual information and 1 bit of relevant auditory information while E simultaneously varied the amount of ir-