For more than six decades now, research and practice in English language teaching has identified the "four skills" — listening, speaking, reading, and writing – as of paramount importance. ESL curricula and textbooks around the world tend to focus, all too often, on just one of the four skills , sometimes to the exclusion of the others. Books, articles, anthologies, research surveys, and conferences typically index or organize their contents according to each of the four skills.
It is perfectly appropriate to thus identify language performance. The human race has fashioned two forms of productive performance, oral and written, and two forms of receptive performance, aural (or auditory) and reading. There are, of course, offshoots of each mode. Lumped together under nonverbal communication are various visually perceived messages delivered through gestures, facial expressions, proximity, and so forth. Graphic art (drawings, paintings, and diagrams) is also a powerful form of communication. But attention to the four different skills does indeed pay off as learners of a second language discover the differences and interrelationships among these four primary modes of performance.