The Marginal Value Foraging Model for Attention
Treat your attention like a foraging animal treats food sources
Dr. Michael Platt draws on mathematical ecologist Eric Charnov's 1976 marginal value theorem to explain how our brains allocate attention. Just as animals leave a food source when its return falls below the environmental average, our brains leave a task or information source when the perceived return drops below the average of all available sources. This is not a bug but a deeply evolved computation that every observed animal performs.
The critical insight is that the richness of your environment determines how quickly you abandon any single source. In a sparse environment (one book, no phone, no tabs), you stick with what you have and extract deep value. In a rich environment (12 browser tabs, phone nearby, TV on), you flit between sources rapidly, never going deep. Even having your phone in the same room degrades working memory because your brain unconsciously includes it in the foraging calculation.
The practical application is environmental impoverishment for deep work: remove devices, reduce available information sources, and make the remaining source the only game in town. Platt also notes that making a device less rewarding (e.g., setting your phone to monochrome mode) measurably reduces checking behavior by lowering the perceived return rate of that source.
- Your brain leaves a task when its perceived return falls below the average return of all available alternatives
- The richer the environment (more devices, tabs, inputs), the faster you abandon any single source
- Even unconscious awareness of an alternative source (phone in the room) degrades focus by being included in the foraging calculation
- You can shift the equation by impoverishing the environment or degrading alternative sources
- Audit Your Foraging EnvironmentBefore starting focused work, inventory every information source available to you: phone, tabs, notifications, screens, other people. Each one your brain registers as a potential foraging patch, pulling you away from your primary task.Pro tipResearch shows your phone must be in a completely separate room, not just face-down or in a bag, to eliminate its effect on working memory.
- Impoverish the EnvironmentPhysically remove all alternative sources. Close all browser tabs except what you need. Put your phone in another room. Turn off notifications. The goal is to make your primary task the only available foraging patch.Pro tipIf you cannot remove your phone, setting it to monochrome (grayscale) mode measurably reduces its appeal as a foraging source.WarningDo not rely on willpower alone. The foraging computation runs below conscious awareness, so environmental design beats discipline.
- Accept the Warm-Up PeriodExpect roughly 10 minutes of difficulty before dropping into focused attention. Platt and Huberman compare this to physical warm-ups before exercise: neural circuits need time to narrow their aperture of attention. This is normal, not a sign of ADHD or deficiency.Pro tipA brief visual focus exercise (staring at a single point for 60 seconds) can help narrow your attentional aperture before cognitive work, based on studies done with students in China.
- Use Focused Visual Attention as a Cognitive Warm-UpBefore deep cognitive work, spend 1-2 minutes focusing your eyes on a small visual target at a set distance. This narrows your visual aperture which research shows carries over into a narrower cognitive aperture, priming your brain for focused rather than exploratory mode.Pro tipConversely, if you need creativity or exploration, spend time looking at wide panoramic views or dispersed visual fields. Panoramic vision is associated with decreased autonomic arousal and broader cognitive exploration.
- Monitor and ResetWhen you notice the urge to check something else, recognize it as the anterior cingulate cortex generating an urgency signal because perceived returns are dropping. Take a breath, re-engage with the material, and remember the signal is a feature of the foraging algorithm, not evidence that you should actually switch.WarningIf you reintroduce a rich source mid-session (check your phone once), you reset your brain's estimate of environmental richness, making it harder to return to focused work.
Platt describes graduate school in the era of dial-up modems, where loading a single web page took 30 seconds or more. In this information-poor environment, students would read entire articles, print them out, and file them. The slow, sparse environment forced deep engagement with each source.
Research cited by Platt shows that when users set their smartphone displays to grayscale (monochrome), they check their phones less frequently and spend less time on them per session.
Studies conducted in China had students focus on a fixation point before sitting down to do cognitive work. The narrow visual aperture primed the brain for focused rather than exploratory cognitive processing.
This framework originates from Eric Charnov's marginal value theorem (1976) in mathematical ecology, which Platt's lab and computer scientists around 2000 began applying to web browsing and digital attention. Platt connects his own experience of graduate school dial-up internet (sparse environment, deep reading) to today's high-speed multi-tab browsing (rich environment, shallow skimming) to illustrate how the same foraging algorithm produces radically different attention patterns depending on environmental richness.