Episode 17 | The Myth of Multitasking

Episode SummaryRight now, as you read this, you are probably not doing only one thing. A document is open. A chat window pulses in another tab. An email preview slides across the corner of the screen. A calendar reminder waits ten minutes away. It feels like several tasks are running at once. The science offers a sharper picture: the screen is multitasking, but your attention is switching. And every switch has a price.In this episode we examine the cost of changing task state. Drawing on Harold Pashler's research on the central bottleneck, Stephen Monsell's work on switch costs, Gloria Mark's two decades of workplace observation, and Sophie Leroy's discovery of attention residue, we show why "quick checks" are rarely quick, why the famous "23 minute recovery" number deserves a more careful telling, and why notifications behave less like information and more like task invitations. The point is not that humans cannot multitask. It is that demanding mental tasks usually compete for the same machinery, and the cost of switching is not lost time alone. It is lost task state.Key Topics CoveredThree behaviors hide under one word: concurrent performance, rapid task switching, and background task managementPashler's psychological refractory period: the central bottleneck at response selectionWickens's multiple resource theory: why some task pairs interfere more than othersThe problem state bottleneck (Borst, Taatgen, van Rijn): switching disrupts the live "where am I" representationSwitch costs in detail: switch cost, preparation effect, residual cost, mixing cost (Monsell, 2003)Goal shifting and rule activation as separable executive operations (Rubinstein, Meyer, Evans)Memory for goals (Altmann, Trafton): suspended goals decay, environmental cues help reactivationAttention residue (Leroy): thoughts about Task A intrude into Task BThe corrected "23 minute" claim: the published number is 25 minutes 26 seconds, with 2.26 intervening working spheresSelf interruption is structural, not just willpower: 18 percent of all switches, 64 percent rise in open officesThe mixed media multitasking literature: from Ophir, Nass, Wagner to recent meta analysesNotifications behave like task invitations even when ignoredExceptions: automaticity, low conflict pairings, and the rare 2.5 percent "supertaskers"Practical takeaway: protect task state, not only timeResearchers MentionedHarold Pashler (UC San Diego) : Dual task interference and the central response selection bottleneckChristopher Wickens (Colorado State University) : Multiple resource theory of attention and workloadStephen Monsell (University of Exeter) : Foundational task switching research and the four core phenomenaDavid E. Meyer (University of Michigan) : Executive control of task switching, the "up to 40 percent" estimateJoshua Rubinstein and Jeffrey Evans (with Meyer) : Goal shifting and rule activation in executive controlNiels Taatgen, Jelmer Borst, Hedderik van Rijn : The problem state bottleneck in multitaskingErik Altmann (Michigan State) and J. Gregory Trafton (US Naval Research Lab) : Memory for goals and interruption resumptionBrian P. Bailey and Shamsi Iqbal : Interruption timing, task boundaries, and attention aware systemsSophie Leroy (University of Washington) : Attention residue and the "ready to resume" planGloria Mark (UC Irvine) : Workplace fragmentation, working spheres, and digital attentionVictor M. Gonzalez (with Mark) : Working spheres in knowledge workLaura Dabbish (Carnegie Mellon) : Self interruption in observed knowledge workEyal Ophir, Clifford Nass, Anthony Wagner (Stanford) : The original "cognitive control in media multitaskers" studyWisnu Wiradhany and Mark Nieuwenstein : Replication and meta analytic caution on the media multitasking linkMelina Uncapher (UCSF) : Cognitive and neural profiles of media multitaskingJason Watson and David Strayer (University of Utah) : Driving distraction research and the discovery of "supertaskers"Walter Schneider and Richard Shiffrin : Controlled versus automatic processingDario Salvucci and Niels Taatgen : Threaded cognition and the multitasking continuumKey Studies and SourcesPashler, H. (1994). "Dual task interference in simple tasks: Data and theory." Psychological Bulletin, 116(2), 220 to 244.Rogers, R.D. and Monsell, S. (1995). "Costs of a predictable switch between simple cognitive tasks." Journal of Experimental Psychology: General, 124(2), 207 to 231.Monsell, S. (2003). "Task switching." Trends in Cognitive Sciences, 7(3), 134 to 140.Rubinstein, J.S., Meyer, D.E., and Evans, J.E. (2001). "Executive control of cognitive processes in task switching." Journal of Experimental Psychology: Human Perception and Performance, 27(4), 763 to 797.Altmann, E.M. and Trafton, J.G. (2002). "Memory for goals: An activation based model." Cognitive Science, 26(1), 39 to 83.Altmann, E.M., Trafton, J.G., and Hambrick, D.Z. (2014). "Momentary interruptions can derail the train of thought." Journal of Experimental Psychology: General, 143(1), 215 to 226.Leroy, S. (2009). "Why is it so hard to do my work? The challenge of attention residue when switching between work tasks." Organizational Behavior and Human Decision Processes, 109(2), 168 to 181.Mark, G., Gonzalez, V.M., and Harris, J. (2005). "No task left behind? Examining the nature of fragmented work." Proceedings of CHI 2005, 321 to 330.Mark, G., Gudith, D., and Klocke, U. (2008). "The cost of interrupted work: More speed and stress." Proceedings of CHI 2008.Dabbish, L., Mark, G., and Gonzalez, V.M. (2011). "Why do I keep interrupting myself? Environment, habit and self interruption." Proceedings of CHI 2011, 3127 to 3130.Mark, G. (2023). Attention Span: A Groundbreaking Way to Restore Balance, Happiness and Productivity. Hanover Square Press.Ophir, E., Nass, C., and Wagner, A.D. (2009). "Cognitive control in media multitaskers." PNAS, 106(37), 15583 to 15587.Watson, J.M. and Strayer, D.L. (2010). "Supertaskers: Profiles in extraordinary multitasking ability." Psychonomic Bulletin and Review, 17(4), 479 to 485.Key Numbers to Remember47 seconds : average screen focus duration in Mark's later screen logging observations (note: this is screen focus from logged digital work, not a universal "human attention span")2.5 minutes : average screen focus in earlier observational work (different study, different method, no clean longitudinal comparison)3 minutes : average time on a single event before another event began (Gonzalez and Mark, 2004)25 minutes 26 seconds : average time to return to same day resumed interrupted work (Mark, Gonzalez, Harris, 2005)<...