This idea of digit, or memory, span might need a little unpacking, especially as Miller was a little vague about what constituted a chunk. I’ve been using the digit span technique with A-level psychology students since 2004 and it’s remarkable how averages rarely shift too far from the research literature. More recently, Cowan has suggested that the capacity of short-term memory is closer to 4 chunks.Īs an aside, these results are highly consistent, both in formal and less controlled settings. According to Miller, the capacity of verbal short-term memory is determined by the number of chunks that can be stored in memory, and not the number of items or the amount of information. Miller found that, on average, people were able to hold between 5 and 9 pieces of information in short-term memory at any one time, or more precisely, 7 +/- 2 chunks. George Miller’s 1956 study remains one of the most cited in the history of psychology, while Jacobs’ has fallen into relative obscurity. However, with the shift towards cognitive psychology from around the 1950s, there was renewed interest in mental functions, including memory, attention and perception. He found that, on average, participants could successfully repeat back around 7 letters and 9 numbers.ĭue to the behaviourist ascendency of the early part of the twentieth century, the study of memory fell out of fashion, predominately because of its internal and, therefore, unobservable nature. These omissions were necessary to ensure equal length and speed of vocalisation. Jacobs initially asked his participants (students from North London Collegiate College) to repeat back nonsense syllables (a technique already utilised by experimental psychologist Hermann Ebbinghaus) but found they varied too greatly in relative difficulty of pronunciation and ‘relative facility to rhythm.’ He, therefore, abandoned this idea and instead chose letters (with the exception of W) and numbers (with the exception of seven). Possibly the first study into such limitation even pre-dates the separation of memory into short-term and long-term components (the first model to incorporate this separation appeared in 1968, although there was general agreement that memory was probably organised in such a way well before Atkinson and Shiffrin’s multi-store model).Ī paper published in the January 1887 edition of Mind by Joseph Jacobs details a study of what is now referred to as memory span. Researchers have known for some time that short-term memory is limited. This latter definition does make sense, in that cognitive schemas and chunking can be thought of as similar mental workarounds.įor us to begin to understand the nature of a chunk, we first need to step slightly away and look at the nature of working memory capacity and why it can be so problematic. Anderson’s ACT-R model, however, views chunks as schema-like structures containing pointers that encode their contents. Cowan, like many other theorists, emphasise the role of long-term memory, in that a chunk must be representative of something we already know. Unfortunately, there isn’t a great deal of consensus on this, even Miller in his famous 1956 paper on capacity noted ‘we are not very definite about what constitutes a chunk of information.’ Cowan (2001) has defined a chunk as ‘groups of items that have strong, preexisting associations to each other but weak associations to other items’. This is all well and good, but what exactly is a chunk and how does chunking help us enhance our limited working memory? In turn, CLT draws on aspects of memory research that go back as far as the late nineteenth century, including studies that attempted to discover the limitations of human memory. The way instructional design can be adapted to help learners cope with these limitation has been encapsulated into a model known as Cognitive Load Theory (CLT). In education, we often describe these terms in relation to cognitive load, or the demands learning places on our limited mental resources. However, chunking also relies heavily upon long-term memory.Ĭhunking is, therefore, related to another aspect of memory known as memory span or digit span (the latter term derives from tests that measure memory span by asking people to repeat back a list of digits that increase incrementally). The process is said to make the recall of information easier because it helps to bypass the inherent limitations of working memory. Chunking describes the process by which individual pieces of information are broken down and grouped together.
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