Cognitive load theory is an instructional theory based on our knowledge of evolutionary psychology and human cognitive architecture. It can be used to provide instructional guidelines for the acquisition of all aspects of a second language by adults and some aspects, primarily reading and writing, of a first language by both children and adults. The theory assumes that knowledge can be divided into biologically primary knowledge that we have evolved to learn easily without conscious effort and biologically secondary knowledge that we have not specifically evolved to learn but can acquire with explicit instruction and conscious effort. Learning to listen to and speak a first language are biologically primary with all other aspects of language learning being biologically secondary. A general cognitive architecture governs the acquisition of biologically secondary knowledge. That architecture includes a working memory that is limited in capacity and duration when dealing with novel information but with no known limits when dealing with familiar information transferred from long-term memory. This architecture governs how we learn and accordingly, also determines the effectiveness of instructional designs.