Understanding how to measure cognitive load is a fundamental challenge for cognitive load theory. In 2 experiments, 155 college students (ages = 17 to 22; 49 men and 106 women) with low domain knowledge learned from a multimedia lesson on electric motors. At 8 points during learning, their cognitive load was measured via self-report scales (mental effort ratings) and response time to a secondary visual monitoring task, and they completed a difficulty rating scale at the end of the lesson. Correlations among the three measures were generally low. Analyses of variance indicated that the response time measure was most sensitive to manipulations of extraneous processing (created by adding redundant text), effort ratings were most sensitive to manipulations of intrinsic processing (created by sentence complexity), and difficulty ratings were most sensitive to indications of germane processing (reflected by transfer test performance). Results are consistent with a triarchic theory of cognitive load in which different aspects of cognitive load may be tapped by different measures of cognitive load.