The first two versions of the UDL Guidelines (version 1.0 and version 2.0) presented the UDL principles in the following order: Provide Multiple Means of Representation, Provide Multiple Means of Action and Expression, and Provide Multiple Means of Engagement. With UDL Guidelines version 2.1 in 2014, a shift was made to this order. Instead of beginning with the UDL principle, “Provide Multiple Means of Representation,” this version begins with “Provide Multiple Means of Engagement.” This shift was meant to highlight the essential role that engagement plays in learning and was motivated by the literature as well as educators’ input.

The UDL Guidelines are not meant to be a prescription or a checklist, but a tool that offers a set of suggestions that can be applied to instructional design to reduce barriers, sustain and honor learners’ multiple identities, and maximize learning opportunities according to specific learning goals.

Each of these networks tend to be spatially distinguishable in the brain: the affective networks are generally situated in the center of the brain, the recognition networks are located in the back/posterior regions, and the strategic (motor) networks are positioned in the anterior/front of the brain. While it should be noted that all the networks work together, CAST focuses on this simplified model of the brain to highlight what is relevant for the learning brain and to try to understand and plan for learner variability.