Constraints on mental effort and working memory

What is the cognitive challenge of constraints of mental effort and cognitive load ?

Students have two major limitations in cognitive processing, the amount of mental effort or concentration available to them and the ability to hold information consciously. Students are easily overwhelmed by trying to concentrate on too complex a task, or to remember too much information.

This video focuses on mental effort and working memory and will enhance the text below.

A major obstacle to learning is cognitive overload, which occurs when the cognitive demands of the situation exceed students’ cognitive capacities. Consider an everyday situation. You are reading an article someone recommended to you. Someone walks in the room talking to get your attention. You receive a phone call you have been waiting for. In moments like these we experience overload and we cannot seem to process everything at once. Overload is a common occurrence because human working memory capacity is limited. We can process only a few pieces of information at one time, and information we don’t process adequately is quickly forgotten (Chandler & Sweller, 1991).

Consider the cognitive effort needed in a typical class period. Students must select and focus on relevant information, ignore distractions and irrelevant information, organize and integrate new material with relevant prior knowledge, make inferences about how new ideas are related to one another, decide which ideas are important and which are less so, interpret the meaning of graphics, such as pictures, charts and diagrams and reconcile those with the instructor’s oral explanations. As students are doing all this, they also make decisions about what information to record in their notes, and what to do about information they don’t understand or completely missed.

The sheer volume of new information is a common cause of overload. As one group of researchers reported

By far the most common problem is that lectures contain too much information. One count has it that an average engineering lecture introduces a new equation every 2.5 minutes and a new variable every 45 seconds (Blikstein & Wilensky, 2010). Imagine sitting through that for an hour!  

Schwartz, Tsang, & Blair, The ABCs of How We Learn, 2016, p. 124

The amount of material is not the only source of cognitive load during lectures. Load increases when the material is unfamiliar, the presentation is fast-paced or disorganized, and when there are frequent distractions. Three types of cognitive load are present in all learning situations:

  1. Essential cognitive load — mental effort needed to carry out the basic aspects of a task
  2. Generative load — mental effort needed to make sense of new information
  3. Extraneous load — mental effort needed to process information that is irrelevant to the task at hand

This video explains each of these sources of cognitive load.

Recommendations to reduce and manage cognitive load

Teachers can’t eliminate cognitive load altogether. The challenge is to reduce or manage cognitive load. This would mean that teachers would try to eliminate or reduce distractions and irrelevant information (extraneous load), help students over learn basic procedures and facts relevant to the task at hand (reduce essential load) and promote deeper processing (generative load) to learn the information more deeply. This video explains strategies teachers can use to reduce and manage cognitive load.

Research has shown that teachers can help manage load by improving the coherence of their lectures and class activities, adapting the pace of instruction to the topic and students, reducing distractions, and asking students to identify possible ways to reduce cognitive load in the class.

    • Improve coherence. Well-organized, coherent information is easier to comprehend and remember (Bransford, 1979). Teachers can improve coherence by making the organization of their lectures explicit, building on prior knowledge, identifying connections among topics throughout the lecture, and segmenting the material into manageable and meaningful chunks. For example, one simple technique is to provide students with a schematic outline of the lecture, which lists major headings, concepts, or questions. Students can use the outline to organize their note taking, and identify how the topics fit together (Kiewra, 2002).
    • Adapt your lecture pace to the topic and the students, and pause at natural transition points. Trying to process the instructor’s talk while deciding what notes to write is challenging. Studies indicate that students’ lecture notes include less than half of the main ideas from the class period (King, 1992; Kiewra, 2002; Armbruster, 2009). One reason is that lectures are fast-paced. Studies show that a typical speaking rate is 120-180 words per minute, and people write at a rate of 12-18 words per minute (Piolat, Olive, & Kellogg, 2005). Lecture information is transient; there is no pause button to allow more time for students to process the information. If they miss an idea, it’s gone. Instructors can moderate their pace using feedback from the class to indicate when the presentation is moving too quickly, e.g., ask students to use a pre-determined hand signal. In addition, natural transition points between lecture topics are opportunities to pause, take questions, and allow students to catch up.
    • Reduce distractions and extraneous material. Any stimulation or activities that interrupt or divert attention from the task at hand can derail learning. When distracted, students stop thinking about the lecture and shift their attention to the source of the distraction. During these momentary shifts they lose their place in the lecture. They then need to backtrack and re-orient to the material. They miss whatever took place while their attention was elsewhere. Some distractions are incidental, e.g., momentary disruptions by students, faulty technology. Others are more frequent. Students’ use of electronic devices in class is a common problem that splits their attention and subverts learning (Kraushaar, & Novak, 2010; Stothart, Mitchum, & and Yehnert, 2015; Ravizza, Uitvlugt, & Fenn , 2016). Some distractions are subtle. For example, misuse of a laptop in lecture distracts the student user, and also distracts students sitting nearby who can see the screen (Fried, 2008; Sana, Weston, & Cepeda, 2013). Teachers also introduce distractions in lecture inadvertently by using graphics or anecdotes that are not directly relevant to the topic at hand. Unfortunately, seductive details, intended to attract students’ attention, often distract them rather than enhance learning (Rey, 2012).
    • Use feedback from students to reduce cognitive load. As experts in their fields, teachers may have trouble seeing their lectures through the eyes of students. Feedback from students can point out specific instructional trouble spots. For example, graduate students in a course on science teaching, identified more than 30 ways to reduce unnecessary mental load related to lecture organization, slides and graphics, the instructor’s projected notes, and the classroom atmosphere and pace. Students recommend that teachers ask three questions periodically to get feedback about the quality and pace of their lecturing.

“When I am lecturing, what do you usually look at or focus on? In general, are you able to read everything and understand what is on the slide? Do you feel you have enough time, too much time, or too little time to process new information that is presented and take necessary notes?” (Carl Wieman Science Education Initiative, 2014)


Working memory capacity is limited. We can process only a few pieces of information at one time. Consequently, students are at risk for cognitive overload when the demands of a learning task exceed their working memory capacity. Instructors can take steps to reduce and manage cognitive load by improving the organization and coherence of instruction, and by trying to reduce sources of unnecessary cognitive load such as distractions and extraneous material. This makes new material more accessible to students and reduces extraneous information so that students can use more of their mental horsepower to process and make sense of the new information. Because there are many potential sources of unnecessary load, instructors should solicit student feedback about specific difficulties they have maintaining attention and processing new information in class.

Recommended readings

Carl Wieman Science Education Initiative (2014). Improving learning by reducing unnecessary mental load, Vancouver, Canada: Retrieved from


Armbruster, B. (2009). Notetaking from lectures. In R. F. Flippo & D. C. Caverly (Eds.), Handbook of college reading and study strategy research (2nd ed., pp. 220–248). New York, NY: Routledge.

Bransford, J. D. (1979). Human cognition: Learning, understanding and remembering. Belmont, CA: Wadsworth.

Carl Wieman Science Education Initiative. (2014). Improving learning by reducing unnecessary mental load. Vancouver, Canada: Author. Retrieved from

Chandler, P., & Sweller, J. (1991). Cognitive load theory and the format of instruction. Cognition and Instruction, 8, 293–332.

deWinstanley, P. A., & Bjork, R. A. (2002). Successful lecturing: Presenting information in ways that engage effective processing. New Directions for Teaching and Learning, 2002, 19–31. San Francisco: Jossey-Bass.

Fried, C. B. (2008). In-class laptop use and its effects on student learning. Computers & Education, 50, 906–914.

Kiewra, K. A. (2002). How classroom teachers can help students learn and teach them how to learn. Theory into Practice, 41, 71–80.

King, A. (1992). Comparison of self-questioning, summarizing, and notetaking-review as strategies for learning from lectures. American Educational Research Journal, 29, 303–323.

Kraushaar, J. M., & Novak, D. C. (2010). Examining the effects of student multitasking with laptops during the lecture. Journal of Information Systems Education, 21, 241–251.

Piolat, A., Olive, T., & Kellogg, R. T. (2005). Cognitive effort during notetaking. Applied Cognitive Psychology, 19, 291–312.

Ravizza, S. M., Uitvlugt, M. G., & Fenn, K. M. (2017). Logged in and zoned out: How laptop internet use relates to classroom learning. Psychological Science, 28, 171–180.

Rey, G. D. (2012). A review of research and a meta-analysis of the seductive details effect. Educational Research Review, 7, 216–237.

Sana, F., Weston, T., & Cepeda, N. J. (2013). Laptop multitasking hinders classroom learning for both users and nearby peers. Computers & Education, 62, 24–31.

Schwartz, D. L., Tsang, J. M., & Blair, K. P. (2016). The ABCs of how we learn: 26 scientifically proven approaches, how they work, and when to use them. New York, NY: Norton.

Stothart, C., Mitchum, A., & Yehnert, C. (2015). The attentional cost of receiving a cell phone notification. Journal of Experimental Psychology: Human Perception and Performance, 41, 893–897.