In cognitive psychology, chunking is a process by which individual pieces of an information set are bound together into a meaningful whole. The chunks by which the information is grouped are meant to improve short-term retention of the material, thus bypassing the limited capacity of working memory and allowing the working memory to be more efficient. A chunk is a collection of basic units that have been grouped together and stored in a person's memory. These chunks can be retrieved easily due to their coherent grouping. It is believed that individuals create higher-order cognitive representations of the items within the chunk. The items are more easily remembered as a group than as the individual items themselves. These chunks can be highly subjective because they rely on an individual's perceptions and past experiences, which are linked to the information set. The size of the chunks generally ranges from two to six items but often differs based on language and culture.
According to Johnson (1970), there are four main concepts associated with the memory process of chunking: chunk, memory code, decode and recode. The chunk, as mentioned prior, is a sequence of to-be-remembered information that can be composed of adjacent terms. These items or information sets are to be stored in the same memory code. The process of recording is where one learns the code for a chunk, and decoding is when the code is translated into the information that it represents.
The phenomenon of chunking as a memory mechanism is easily observed in the way individuals group numbers, and information, in day-to-day life. For example, when recalling a number such as 12101946, if numbers are grouped as 12, 10, and 1946, a mnemonic is created for this number as a month, day, and year. It would be stored as December 10, 1946, instead of a string of numbers. Similarly, another illustration of the limited capacity of working memory as suggested by George Miller can be seen from the following example: While recalling a mobile phone number such as 9849523450, we might break this into 98 495 234 50. Thus, instead of remembering 10 separate digits that are beyond the putative "seven plus-or-minus two" memory span, we are remembering four groups of numbers. An entire chunk can also be remembered simply by storing the beginnings of a chunk in the working memory, resulting in the long-term memory recovering the remainder of the chunk.