Why you run out of brain before you run out of day -- and what to do about it

From July 2025

Someone I respect quite a bit said something I disagreed with quite a lot. He said that time was his most constrained resource. I don’t think that is quite right — attention (which is related to time, but is not the same) is our most constrained resource. Perhaps because I’m no longer 25, I run out of ability to process information before I run out of hours in the day. By about 10 pm many nights, I’m laying on the couch in my study with my eyes closed, horrified by the thought of trying to jam another fact into my brain or make another decision.

[Sometimes this has led to mild tension in Rancho Kaplan. When the kids were younger and had to be ferried to different places, Amy deeply valued my ability to perform what she called Fox-and-chicken analysis (FCA), after the old riddles about how you get a fox, a chicken and some corn across a river. She would exclaim, “Great you solve complicated logistical problems for clients all day, but when I need to solve a logistical problem for me, all you want to do is look at cat videos.” In my defense, cat videos are very soothing.

Most of us in enterprise technology have a demanding job – our work creates cognitive load, which requires attentional capacity. Not only is attentional capacity finite, it varies over the course of the day, week and our careers. So we must manage others’ cognitive load and our own attention

< 1 > Our work creates cognitive load, which requires attentional capacity

Anything we do — building a business case, designing an architecture, drafting a memo, writing a function — creates cognitive load. Australian educational psychologist John Sweller proposed that complex task create cognitive load, which he divided into three parts — intrinsic load (task complexity), extraneous load (related to poor information design) and Germane load (related to learning).

In “Attention and Effort” future Nobel Laurate Daniel Kahnemann modeled attention as a limited resource that we allocate among competing mental tasks. He divided tasks into effortless (e.g. walking) and effortful or System 2 talks (all the stuff clients expect us to do every day).

(You can buy a use copy for USD 198.00 or download a PDF here: https://www.academia.edu/47032081/Attention_and_Effort)

You can think of Cognitive Load as the “demand” side of our intellectual experience and attention as the “supply side.” I’ve written about Mihaly Csikszentmihalyi’s concept of flow. German psychologists Stefan Engeser and Falko Rheinberg argue that flow state occurs when balance exists between cognitive load and available attention. (I haven’t read this yet, but I plan to: https://link.springer.com/article/10.1007/s11031-008-9102-4)

< 2 > Attention isn’t constant

Yes, attention is limited. Harvard cognitive psychologist George Miller proposed “The number of objects an average human can hold in working memory is 7 +/- 2” in 1956. (Interesting historical footnote. Telecom sector folklore holds that Millers research influenced the structure of NANPA phone numbers, which have 7 digits absent area code. This is false. The Bell system started standardized on seven digit local phone numbers in the 1951.) Much of the early research on attention as a constraint looked into how many things you could keep in working memory at one time.

As my experience laying on the couch in my study demonstrates, even for a given person attentional capacity is not constant. We all have circadian rhythms – I value “coffee shop” time because I am most alert and mentally focused in the morning. Even more importantly again Daniel Kahnemann points out that sustained attention draws down attentional capacity over the course of a day and reduces effectiveness in effortful/system 2 thinking. There are a bunch of papers here to put on my reading list (which I will not get through because, sadly, I do not have unlimited attentional capacity.)

• Boksem & Tops (2008). Mental fatigue: Costs and benefits.

• Warm, J. S., Parasuraman, R., & Matthews, G. (2008). Vigilance Requires Hard Mental Work and Is Stressful. Human Factors.

• Van der Linden et al. (2003). Mental fatigue and the control of cognitive processes: Effects on perseveration and planning.

• Van der Linden (2011). The impact of mental fatigue on attention and error-monitoring.

• Muraven, M., & Baumeister, R. F. (2000). Self-regulation and depletion of limited resources: Does self-control resemble a muscle? Psychological Bulletin.

The intersection of attentional capacity and vigilance is fascinating to me. How much mental toughness must a Lewis Hamilton or a Max Verstappen have to sustain the concentration required to pilot a F1 car for 140mph over the course of two hours? (As always, Ida Pagter Kristensen I included the Formula 1 reference for your benefit.)

< 3 > We must manage others’ cognitive load and our own attention

So, you might ask, what the heck do you do about this?

• Worry about the cognitive load of those around us. Much of the classic communications stuff – structure, clarity, precision – comes from a desire to manage our cognitive load on the people around us. What elicits support for a plan? The goat rodeo of a presentation, or one organized into a situation, a complication and a resolution. Who builds allies? The person who wanders into your office and rambles about who-knows-what or the person who can concisely explain what you need to know and what you might do about it. Structure is compassion. Disorganized communication is an act of selfishness and insensitivity.

• Manage your own attentional capacity over the course of the day. Some of this is obvious: sleep, exercise, etc. A lot of it involves observing yourself closely and understanding when and how your attentional capacity draws down over the course of the day. Just as a cyclist seeking the yellow jersey must figure out when to draft and when to attack, you must figure out when to be intellectually on the front foot versus not. Everyone says find a big block of time when you wont get distracted to work on a major effort. That’s not always true for everyone. I often work in twenty minute chunks when I have to write something complicated and then switch to another less mentally demanding task for a little while. That works for me, and might not work for others.

• Understand when cognitive load exceeds attentional capacity – these are the times with the greatest risk for sloppy decision-making or uninspirational behavior. I never love unstructured communications – but I am most at risk of being snarky or dismissive when faced with the combination of unstructured communications and I am mentally exhausted.

• Build attentional capacity over time. The biochemistry of stress reduces attentional capacity. Dissonance in values between you and your environment increases stress – and therefore reduces attentional capacity. Finding a mechanism for achieving consonance between you and the environment reduces your baseline level of stress, increasing attentional capacity – and that expands not only your happiness, but also your professional impact.