Authors: Matt Zuckerman, MD; Alison Hayward; MD, MPH
Editor: Benjamin Schnapp, MD, MEd 

A Case

Matt is an Emergency Medicine intern preparing for this week’s conference. He attempts to watch one of the suggested Free Open-Access Medical Education (FOAM) videos about diabetic ketoacidosis (DKA) while washing the dishes and keeping an eye on his 12-month-old daughter. He finished the video twice but each time he finds that he can’t remember anything. Matt feels frustrated because he knows that he’s attempting to do three things at once and doing them all poorly. Between his clinical responsibilities and trying to keep things going around the house, he rarely gets time alone to study. He’s worried that the only option is going to conference unprepared, neglecting his daughter, or switching to take out meals. He ponders his dilemma and realizes that the main issue isn’t necessarily needing more time, but figuring out some way to process everything more efficiently. 

Background

Christopher Wickens created the multiple resource theory model to explain why some tasks are easier to do simultaneously (walking and chewing gum) while others are much harder (talking and reading). He recognized that several different schools of thought were attempting to explain the same phenomenon in different ways. 

Historical explanations of dual-task performance relied on the mechanical analogy of workload and power. As computers became more popular, the conception of learners having a central processor also became popular. Kahneman’s 1973 book, “Attention and Effort,” attempted to explain human performance using a general pool of mental “effort” without differentiated resources.² Other scientists in the field (Isreal, Wickens, Chesney, & Donchin) noted that resources seemed to be specialized, as the nature of simultaneous tasks affected our ability to do them. In an expansive review of the literature, Wickens attempted to reconcile these theories and integrate the experimental literature.

Wickens posited that tasks compete for a shared pool of resources. Simultaneous tasks that require similar resources may interfere with each other (e.g. reading a book while listening to another book). Performing two tasks simultaneously will usually reduce the efficiency of each task, however this effect is not the same for every task or every operator. In general however, tasks are easier to perform and most efficient when done without competing demands. Even listening to music (which requires few cognitive resources) while driving creates occasional moments when the driver is focused on the music to the exclusion of the road, or is focused on navigating and misses part of a song. In a multitasking scenario, the reduction in efficiency resulting from performing any given tasks simultaneously is known as task interference.^3,4

Modern takes on this Theory

The modern ubiquity of mobile phones increases the tendency to multitask as we constantly respond to texts or lookup information while driving, walking, or engaging in live meetings. This ubiquitous source of work and pleasure is an unanticipated driver of multitasking, not conceived of when Wickens wrote his paper in 1981.

Based on experimental testing of multiple resource theory, Boles has suggested adding tactile input (haptics) as a separate modality of input apart from visual and auditory. For example, pilots that are focusing on a visual display and listening to audio instructions perform better with tactile warnings communicated with vibrations than with visual warnings. These researchers point out that tactile input is an underutilized modality in the design of safety alerts, which tend to rely heavily on visual attention.⁹ Boles additionally differentiated the auditory and visual processing modalities, breaking auditory processing into “linguistic” and “emotional” components, and visual processing into “positional spatial” versus “quantitative” components. For example, reviewing recent lab values in chart format likely requires different visual resources from reviewing a spreadsheet of numbers.^10,11 Practically, this means we can actually process more information simultaneously if we more effectively understand how to separate the input channels. Cognitive load has also been found to occur in potentially unexpected places. For example, it has been observed that visual information can create more interference based on distance in space. If information must be gathered from different sources that require only eye movements, this would cause a lower level of visual interference than information that requires head movement to acquire.⁸

Other Examples of Where this Theory Might Apply

This theory has important implications for medical education as learners are frequently asked to perform multiple tasks simultaneously. Consideration should be given to  multiple resource theory when planning any lecture or workshop, in order to optimize the use of inputs while minimizing task interference for learners. For example, any potential distractions should be avoided while learners are heavily cognitively engaged with learning a new procedural skill, as learners will have few cognitive resources to spare. The theory also supports the idea of multimedia education, as communicating information through different channels helps learners activate multiple areas of the brain and avoid cognitive overload.

Multiple resource theory can also help explain the task efficiency learners gain when procedural tasks become more automatic and require less processing. The surgical intern who must focus solely on tying her knots becomes the senior who can tie knots effortlessly while monitoring bleeding and case progression. It can also help explain why the ED provider can passively monitor the ambient audio conversations of the charge nurse and simultaneously visually review the CT scan on a trauma patient.

Modern high fidelity simulation design should factor these concepts into simulations. Requiring a provider to handle multiple patients at once or monitor vital signs while EMS gives report reflect the demands on multiple cognitive resources that are placed on a provider in the real world. Simulating scenarios in which interruptions in care take place helps trainees to practice and improve on handling and prioritizing multiple types of input at the same time. Studies suggest that high stress and high cognitive load situations with frequent interruptions may result in significant medical errors.^{12, 13, 14} Through simulation exercises and through senior shifts acting as attending physicians, residents can develop strategies to manage and decrease the cognitive load and optimize their multitasking abilities. 

The model also has important implications for clinical practice and contributes to how we present information on patient monitors and in electronic medical records. Design of safety-related alerts must take into account that using different resources will likely increase staff responsiveness to a potential error or problem. For example, some monitors use flashing lights, rather than just auditory stimuli, to indicate a concerning event. Using tactile vibrating phones that specifically alarm for critically ill patients could increase responsiveness when compared to adding yet another beeping machine to the hospital environment. Color-coding labs or vital signs that are abnormal or providing the option of displaying values in a graphical format helps to highlight the abnormal values by engaging different parts of the brain and increases likelihood of providers taking note and responding appropriately. 

Limitations of this Theory

The limitations of multiple resource theory include variability in measuring efficiency of tasks, as well as the challenge of estimating a ‘baseline’ level of demand for tasks, since the level of demand for a given task may be very reliant on the experience level of the individual in question with the task.¹⁵

The multiple resource model assumes that resources will be deployed logically and optimally towards each task being completed. More recent studies suggest that this may not be the case: there are tasks which are more engaging than others, such that they override other tasks. Studies have found that drivers became so engrossed by cell phone conversations that they failed to continue to pay attention to their surroundings, despite the fact that there is little overlap in resource allocation between the two tasks.^3,16,17

Returning to the case…

Matt realizes that he is struggling to process visual inputs from his FOAM video while simultaneously looking at the dishes and his daughter. He instead finds an audio FOAM resource on DKA that he listens to while singing to his daughter about DKA and washing the dishes. In this way he separates visual from auditory inputs and reduces his mental load thinking about what his daughter is doing by entertaining her with a fun song. He also reinforces the material he is learning through simultaneous repetition. By the time he is done with the podcast, the dishes are clean, his daughter is ready for bed, and he is prepared for his conference small group on DKA.

References:

1. Wickens CD. Processing resources in attention. in Parasuraman R and Davies R, eds. Varieties of attention. New York, NY: Academic Press,1984.
2. Kahneman D. Attention and Effort. Englewood Cliffs, NJ: Prentice-Hall;1973.
3. Pashler, H. Dual Task Interference in Simple Tasks: Data and Theory. Psychological Bulletin. 116(2):220–244. 
4. Wickens CD, Sandry D, & Vidulich, M. Compatibility & Resource Competition. Human Factors, 1983;25,227-248.
5. Wickens CD. Processing resources and attention. Multiple-task performance. Mar 2;1991:3-4.
6. Boles D. Multiple Resources. International Encyclopedia of Ergonomics and Human Factors, Vol 3. 
7. Wickens CD. Multiple resources and performance prediction. Theoretical issues in ergonomics science. 2002 Jan 1;3(2):159-77.
8. Wickens CD. Multiple resources and mental workload. Human factors. 2008 Jun;50(3):449-55.
9. Sklar AE, Sarter NB. Good vibrations: Tactile Feedback in Support of Attention Allocation and Human-Automation Coordination in Event-Driven Domains. Human Factors. Human Factors. 1999 Dec 41(4),543–552.
10. 10.Boles DB, Law MB. A simultaneous task comparison of differentiated and undifferentiated hemispheric resource theories. Journal of Experimental Psychology: Human Perception and Performance. 1998 Feb;24(1):204.
11. Boles DB. Lateralized spatial processes and their lexical implications. Neuropsychologia. 2002 Jan 1;40(12):2125-35.
12. 12.Pawar S, Jacques T, et al. Evaluation of cognitive load and emotional states during multidisciplinary critical care simulation sessions. BMJ Simul Technol Enhanc Learn. 2018 Apr;4(2):87-91.
13. 13.Li SY, Magrabi F, et al. A systematic review of the psychological literature on interruption and its patient safety implications. J Am Med Inform Assoc. 2012 Jan-Feb;19(1):6-12.
14. 14.Ratwani RM, Fong A, et al. Emergency Physician Use of Cognitive Strategies to Manage Interruptions. Ann Emerg Med. 2017 Nov;70(5):683-687.
15. 15.Wickens CD & Boles D. The Limits of Multiple Resource Theory. University of Illinois Engineering Psych. Lab Tech Report; Nov 1983.
16. 16.Strayer DL, Drews FA. Cell-Phone–Induced Driver Distraction. Current Directions in Psychological Science, 2007;16(3),128–131.
17. 17.Strayer DL, Johnston W. Driven to distraction: dual task studies of simulated driving and conversing on a cellular telephone. Psychological Science,12,462-466.