Episode Summary How many things can you hold in your mind at once? In 1956, psychologist George Miller declared that the answer was "seven, plus or minus two", a number that became one of psychology's most famous findings. But modern research tells a different story: the real limit is just four. In this episode, we explore the science of working memory, the mental workspace where thinking happens. We meet George Miller, who opened his landmark paper with the playful confession that he had "been persecuted by an integer." We discover why his key insight wasn't the number itself, but the distinction between bits and chunks: while we can only hold about four items, the size of those items depends on our expertise. A chess master and a beginner both hold four chunks, but the master's chunks contain entire game positions. We also explore Alan Baddeley's revolutionary working memory model, which replaced the simple "short-term store" with a sophisticated multi-component system that just celebrated its 50th anniversary. And we learn why working memory training programs, despite early optimism, don't seem to increase core capacity in adults, but building expertise does. Key Topics Covered - George Miller's 1956 paper "The Magical Number Seven, Plus or Minus Two" - The cognitive revolution and the birth of cognitive science - The crucial distinction between bits (information units) and chunks (meaningful units) - Recoding: how we combine smaller units into larger meaningful chunks - Nelson Cowan's 2001 revision: why the true limit is closer to 4 - The focus of attention and embedded-processes model - Alan Baddeley's working memory model and its components: - The phonological loop (inner voice and inner ear) - The visuospatial sketchpad (mind's eye) - The central executive (attention controller) - The episodic buffer (added in 2000) - Visual working memory studies by Luck and Vogel - How chunking expands effective capacity through expertise - Working memory training: why it doesn't transfer to general intelligence - The digital age challenge: smartphones and cognitive capacity Researchers Mentioned - George Miller (1920-2012) — Father of cognitive psychology, author of the "Magical Number Seven" paper, co-founder of Harvard's Center for Cognitive Studies, creator of WordNet - Nelson Cowan (University of Missouri) — Proposed the 4-chunk limit, developed the embedded-processes model - Alan Baddeley (University of York) — Co-creator of the working memory model, proposed the episodic buffer - Graham Hitch (University of York) — Co-creator of the working memory model with Baddeley - Herbert Simon — Reportedly told Miller "George had the right idea, but the wrong number" - Steven Luck (UC Davis) — Visual working memory research - Edward Vogel (University of Chicago) — Visual working memory, discovered Contralateral Delay Activity - Adriaan de Groot — Chess expertise and chunking (1946/1965) - William Chase & Herbert Simon — Chess expertise studies (1973) - Jerome Bruner — Co-founded Center for Cognitive Studies with Miller Key Studies & Sources - Miller, G.A. (1956). "The magical number seven, plus or minus two: Some limits on our capacity for processing information." *Psychological Review*, 63(2), 81-97. - Cowan, N. (2001). "The magical number 4 in short-term memory: A reconsideration of mental storage capacity." *Behavioral and Brain Sciences*, 24(1), 87-185. - Baddeley, A.D. & Hitch, G.J. (1974). "Working memory." In *The Psychology of Learning and Motivation* (Vol. 8, pp. 47-89). - Baddeley, A. (2000). "The episodic buffer: A new component of working memory?" *Trends in Cognitive Sciences*, 4(11), 417-423. - Luck, S.J. & Vogel, E.K. (1997). "The capacity of visual working memory for features and conjunctions." *Nature*, 390, 279-281. - Hitch, G.J., Allen, R.J., & Baddeley, A.D. (2025). "The multicomponent model of working memory fifty years on." *Quarterly Journal of Experimental Psychology*, 78(2), 222-239. - Simon, H.A. (1974). "How big is a chunk?" *Science*, 183(4124), 482-488. Key Numbers to Remember - 1956 — Year Miller published "The Magical Number Seven" - 7 ± 2 — Miller's original estimate of memory span - 4 — Cowan's revised estimate of true working memory capacity - 23,800+ — Number of citations for Miller's 1956 paper - 6,200+ — Number of citations for Cowan's 2001 paper - 2.6 bits — Mean channel capacity for unidimensional stimuli - 1-2 seconds — How quickly phonological traces decay without rehearsal - ~2 seconds — The rehearsal window (how many words you can say predicts span) - 50 years — Age of Baddeley's working memory model (1974-2024) - 50,000 — Approximate number of domain-specific chunks experts possess Memorable Quotes "My problem is that I have been persecuted by an integer. For seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals."George Miller, opening of the 1956 paper "George had the right idea, but the wrong number."Herbert Simon to George Miller (reported) "The span of immediate memory seems to be almost independent of the number of bits per chunk."George Miller (1956) "The process of recoding is a very important one in human psychology... the kind of linguistic recoding that people do seems to me to be the very lifeblood of the thought processes."George Miller (1956) "A single, central capacity limit averaging about four chunks is implicated along with other, noncapacity-limited sources."Nelson Cowan (2001) "If we did hold more than just a few items at a time, it becomes too difficult to learn how to manage so many pieces of information at once."Soni & Frank (2025), on why capacity limits exist The Big Idea The human mind has a hard limit on how many things it can juggle simultaneously, about four chunks, not seven. But this isn't a design flaw; it's what enables us to learn effective management strategies. The key insight is that capacity is measured in chunks, not bits. Through expertise and practice, we build larger and more sophisticated chunks, effectively expanding what our limited capacity can accomplish. A phone number is easier as 555-123-4567 (three chunks) than as ten separate digits. A chess master sees meaningful patterns where a novice sees scattered pieces. Understanding this bottleneck (and the chunking trick that helps us work around it) changes everything about how we should de...