| Working memory is widely acknowledged as having limited capacity. An early quantification of the capacity limit associated with short-term memory was the "[[The Magical Number Seven, Plus or Minus Two|magical number seven]]" suggested by Miller in 1956.<ref name="miller">{{Cite journal|author=Miller GA |title=The magical number seven plus or minus two: some limits on our capacity for processing information |journal=Psychological Review |volume=63 |issue=2 |pages=81–97 |date=March 1956 |pmid=13310704 |doi=10.1037/h0043158|citeseerx=10.1.1.308.8071 }} Republished: {{Cite journal|author=Miller GA |title=The magical number seven, plus or minus two: some limits on our capacity for processing information. 1956 |journal=Psychological Review |volume=101 |issue=2 |pages=343–52 |date=April 1994 |pmid=8022966 |doi=10.1037/0033-295X.101.2.343}}</ref> He claimed that the information-processing capacity of young adults is around seven elements, which he called "chunks", regardless of whether the elements are digits, letters, words, or other units. Later research revealed this number depends on the category of chunks used (e.g., span may be around seven for digits, six for letters, and five for words), and even on features of the [[chunking (psychology)|chunks]] within a category. For instance, span is lower for long than short words. In general, memory span for verbal contents (digits, letters, words, etc.) depends on the phonological complexity of the content (i.e., the number of phonemes, the number of syllables),<ref>{{Cite journal|last=Service|first=Elisabet|date=1998-05-01|title=The Effect of Word Length on Immediate Serial Recall Depends on Phonological Complexity, Not Articulatory Duration|journal=The Quarterly Journal of Experimental Psychology Section A|volume=51|issue=2|pages=283–304|doi=10.1080/713755759|issn=0272-4987}}</ref> and on the lexical status of the contents (whether the contents are words known to the person or not).<ref>{{Cite journal|first1=Charles |last1=Hulme |first2=Steven |last2=Roodenrys |first3=Gordon |last3=Brown |first4=Robin |last4=Mercer |date=November 1995 |title=The role of long-term memory mechanisms in memory span |journal=British Journal of Psychology |volume=86 |issue=4 |pages=527–36 |doi=10.1111/j.2044-8295.1995.tb02570.x}}</ref> Several other factors affect a person's measured span, and therefore it is difficult to pin down the capacity of short-term or working memory to a number of chunks. Nonetheless, Cowan proposed that working memory has a capacity of about four chunks in young adults (and fewer in children and old adults).<ref>{{Cite journal|first1=Nelson |last1=Cowan |year=2001 |title=The magical number 4 in short-term memory: A reconsideration of mental storage capacity |journal=Behavioral and Brain Sciences |volume=24 |issue=1 |pages=87–185 |doi=10.1017/S0140525X01003922 |pmid=11515286|doi-access=free }}</ref> | | Working memory is widely acknowledged as having limited capacity. An early quantification of the capacity limit associated with short-term memory was the "[[The Magical Number Seven, Plus or Minus Two|magical number seven]]" suggested by Miller in 1956.<ref name="miller">{{Cite journal|author=Miller GA |title=The magical number seven plus or minus two: some limits on our capacity for processing information |journal=Psychological Review |volume=63 |issue=2 |pages=81–97 |date=March 1956 |pmid=13310704 |doi=10.1037/h0043158|citeseerx=10.1.1.308.8071 }} Republished: {{Cite journal|author=Miller GA |title=The magical number seven, plus or minus two: some limits on our capacity for processing information. 1956 |journal=Psychological Review |volume=101 |issue=2 |pages=343–52 |date=April 1994 |pmid=8022966 |doi=10.1037/0033-295X.101.2.343}}</ref> He claimed that the information-processing capacity of young adults is around seven elements, which he called "chunks", regardless of whether the elements are digits, letters, words, or other units. Later research revealed this number depends on the category of chunks used (e.g., span may be around seven for digits, six for letters, and five for words), and even on features of the [[chunking (psychology)|chunks]] within a category. For instance, span is lower for long than short words. In general, memory span for verbal contents (digits, letters, words, etc.) depends on the phonological complexity of the content (i.e., the number of phonemes, the number of syllables),<ref>{{Cite journal|last=Service|first=Elisabet|date=1998-05-01|title=The Effect of Word Length on Immediate Serial Recall Depends on Phonological Complexity, Not Articulatory Duration|journal=The Quarterly Journal of Experimental Psychology Section A|volume=51|issue=2|pages=283–304|doi=10.1080/713755759|issn=0272-4987}}</ref> and on the lexical status of the contents (whether the contents are words known to the person or not).<ref>{{Cite journal|first1=Charles |last1=Hulme |first2=Steven |last2=Roodenrys |first3=Gordon |last3=Brown |first4=Robin |last4=Mercer |date=November 1995 |title=The role of long-term memory mechanisms in memory span |journal=British Journal of Psychology |volume=86 |issue=4 |pages=527–36 |doi=10.1111/j.2044-8295.1995.tb02570.x}}</ref> Several other factors affect a person's measured span, and therefore it is difficult to pin down the capacity of short-term or working memory to a number of chunks. Nonetheless, Cowan proposed that working memory has a capacity of about four chunks in young adults (and fewer in children and old adults).<ref>{{Cite journal|first1=Nelson |last1=Cowan |year=2001 |title=The magical number 4 in short-term memory: A reconsideration of mental storage capacity |journal=Behavioral and Brain Sciences |volume=24 |issue=1 |pages=87–185 |doi=10.1017/S0140525X01003922 |pmid=11515286|doi-access=free }}</ref> |