Cognitive Load is a term (used in psychology and other fields of study) that refers to the load on working memory during problem solving, thinking and reasoning (including perception, memory, language, etc.).
Most would agree that people learn better when they can build on what they already understand. But the more things a person has to learn in a short amount of time, the more difficult it is to process information in working memory.
Consider the difference between having to study a subject in one's native language versus trying to study a subject in a foreign language. The cognitive load is much higher in the second instance because the brain must work to translate the language while simultaneously trying to understand the new information.
Another aspect of cognitive load theory involves understanding how many discrete units of information can be retained in short term memory before information loss occurs. An example that seems to be commonly cited of this principle is the use of 7-digit phone numbers, based on the theory that most people can only retain seven "chunks" of information in their short term memory.
Cognitive Load Theory, as defined by Sweller (1988), states that optimum learning occurs in humans when the load on working memory is kept to a minimum to best facilitate the changes in long term memory.
The history of Cognitive Load Theory
The history of cognitive load theory can be traced back to the beginning of Cognitive Science and the work of G.A. Miller (1956). Miller was perhaps the first to suggest our working memory capacity was limited in his classic paper (Miller, 1956). He suggested we are only able to hold seven plus or minus two digits of information in our short term memories. Miller's early work was built upon by many researchers in the ensuing decades. Perhaps most notably by that of Simon and Chase (1973) who also used the term "chunk" to describe how experts use their short term memories. As novices learn, they begin to see patterns in the world around them. These patterns can be combined with other patterns... this chunking of memory components has also been described as schema construction.
John Sweller developed cognitive load theory while studying problem solving (Sweller, 1988). While studying learners as they solved problems, he and his associates found that learners often use a problem solving strategy called means-ends analysis. He suggests problem solving by means-ends analysis requires a relatively large amount of cognitive processing capacity, which may not be devoted to schema construction. Instead of problem solving, Sweller suggests Instructional designers should limit cognitive load by designing instructional materials like worked-examples, or goal-free problems.
In the 1990s, Cognitive load theory was applied in several contexts and the empirical results from these studies led to the demonstration of several learning effects: the completion-problem effect (Paas, 1992); Modality effect (Moreno & Mayer, 1999; Mousavi, Low, & Sweller, 1995); Split-attention effect (Chandler and Sweller, 1992); and the Worked-example effect (Sweller & Cooper, 1985; Cooper & Sweller, 1987).
The human cognitive architecture and Instructional design
Cognitive load theory has been used to describe the architecture of human cognition. It has been suggested that Cognitive load has broad implications for Instructional design (Sweller, 1999). This theory provides a general framework for instructional designers for it allows them to control the conditions of learning within an environment or more generally within most instructional materials. Specifically it provides empirically-based guidelines that help instructional designers to minimize extraneous cognitive load during learning.
John Sweller's theory employs information processing theory to emphasize the inherent limitations of working memory. In addition it uses schemas as the relevant unit of analysis for the design of instructional materials.
This theory differentiates between three types of cognitive load: intrinsic cognitive load, germane cognitive load, and extraneous cognitive load (Sweller, van Merriлnboer, and Paas, 1998).
Intrinsic cognitive load
The term "Intrinsic cognitive load" was first described by Chandler and Sweller (1991). Accordingly all instruction has an inherent difficulty associated with it (e.g., the calculation of 2 + 2, versus solving a differential equation ). This inherent difficulty may not be altered by an instructor. However many schemas may be broken into individual "subschemas" and taught in isolation, to be later brought back together and described as a combined whole (Clark, Nguyen, and Sweller, 2006).
Extraneous cognitive load
Extraneous load is that load which instructional designers do have some ability to control. This load can be attributed to the design of the instructional materials.
Sweller provides a wonderful example of extraneous cognitive load in his 2006 book, when he describes two possible ways to describe a square to a student (Clark, Nguyen, and Sweller, 2006). A square is a visual and should be described using a visual medium. Certainly an instructor can describe a square in a verbal medium, but it takes just a second and far less effort to see what the instructor is talking about when a learner is shown a square, rather than having one described verbally. In this instance, the efficiency of the visual medium is preferred. This is because it does not unduly load the learner with unnecessary information. This unnecessary cognitive load is described as extraneous cognitive load.
Germane cognitive load
Germane load was first described by Sweller, van Merrienboer and Paas in 1998. It is that load devoted to the processing, construction and automation of schemata. While intrinsic load is generally thought to be immutable, instructional designers can manipulate extraneous and germane load. It is suggested that they limit extraneous load and promote germane load (Sweller, van Merrienboer & Paas, 1998).
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Источник: http://en.wikipedia.org/wiki/Cognitive_load | 
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