John Sweller's cognitive load theory (1988) proposes that the human working memory has limited capacity — and that instructional design must account for this limit or learning fails.

Three Types of Cognitive Load

• Intrinsic load: Complexity inherent to the material itself. A simple concept has low intrinsic load; differential equations have high intrinsic load.
• Extraneous load: Load caused by poor instructional design — irrelevant information, confusing layouts, unnecessary elements. This load wastes capacity without aiding learning.
• Germane load: Load that directly contributes to learning — forming schemas, connecting new information to existing knowledge.

The Design Implication

The goal is to minimize extraneous load and maximize germane load within the working memory capacity limit. When extraneous load consumes too much capacity, germane load — actual learning — gets crowded out.

Applications

• Worked examples are more effective than problem-solving for novices (reduces extraneous search)
• Split-attention effect: separating text from relevant diagrams increases cognitive load — integrate them
• Redundancy effect: explaining a diagram in text that the diagram already shows perfectly wastes capacity

Reference:

Wikipedia: Cognitive Load Theory

https://en.wikipedia.org/wiki/Cognitive_load_theory