The application of cognitive load theory has been at the forefront of work in cognition and learning for some time. Cognitive load theory seeks to explain how and why some material is more difficult to learn and is based on the proposition that the human brain uses two types of memory: short-term (working) and long-term (storage) memory. Cognitive load measurements are relative, transient, and subject to a significant number of empirical and time-sensitive factors. Measures of cognitive load should therefore be treated with caution and differentiation between germane, extraneous, and intrinsic load remains challenging for all instruments. Overall mental performance is a multidimensional construct, and cognitive load theory does not take account of factors such as the influence of individual goals, or beliefs on cognitive performance. It has been proposed that cognitive load theory implies that the physical integration of multiple sources of information is generally beneficial for learners, as happens when, for example, text and images are combined.