Manifesto
Slow down to see who will use it
Tools are born with an expiry date: they solve a now that is bound to change. The human brain has no expiry date, and what varies in it is the singularity of each person. Understanding how it works, and the body it lives in, is what makes a designer future-proof. No method and no technique will come out of here. What I offer is an invitation to depth.
The technology you build with
changes generation every few years
The brain of the person using it
practically unchanged for 300,000 years
The top one runs; the bottom one takes minutes to cover what the top one covers in seconds. The real difference is larger than the screen can show, and you are designing for both at once.
Design thinking has become a buzzword, a rigid process that dispenses with critical thinking.
Two things move at very different speeds, and we design for both at once. On one side, the tool: frameworks that update overnight, libraries arriving in an avalanche, models promising a finished screen in one click. On the other, the person who will use it, with the same attention, the same memory and the same reactions as thousands of years ago. The first has changed so much since you started working that your portfolio from five years ago looks like another profession. The second has not changed at all.
Attention, working memoryThe mental space where the person holds what they are using right now. It holds about four things, and they fade in seconds if they are not used.See it in Memory →See in the glossary →, the consolidation of a memory and the emotional response work today almost the way they worked in the Paleolithic. What those limits do to a decision is the subject of Thinking, Fast and Slow, which Daniel Daniel KahnemanHalf the work this catalogue cites passes through him: anchoring, availability, the endowment effect, peak–end, the two systems.5 references in this work:2011Thinking, fast and slow1966Pupil diameter and load on memory1993When more pain is preferred to less: adding a better end1990Experimental tests of the endowment effect and the Coase theorem1991Anomalies: the endowment effect, loss aversion, and status quo biasSee on Wikipedia ↗See in the bibliography → published in 2011. Five menu options at once, an endless form, a deadline invented to force the choice: each of those shortcuts ignores a limit that is not up for negotiation. And the cost of those shortcuts does not show up in the next day’s metric, because nobody abandons a product complaining about cognitive load.
Slowing down is not abandoning the tool. It is looking at it knowing the size of what is on the other side. Instead of applying the newest checklist and hoping, you can form a hypothesis about how the person thinks and learn from what happens. Prototyping fast is great. Testing calmly is what tells you where the flow is charging more than it should.
Breaking a long process into smaller parts gives the person somewhere to plant a foot. Showing how far they have come turns waiting into a route. None of this is against the tool, and this is where the misunderstanding usually lives: understanding how attention, memory and emotion work is not for distrusting what you build with. It is for knowing what that thing is charging the person who will use it.
There is a second suspicion, and it came later. What we call a UX law is almost never a law: it is a finding measured in a few dozen people, almost always university students, almost always in one country. It becomes a law somewhere between the study and the drawing board, and once it does, it stops being checked. Nobody asks a law for its sample.
And when the word neuroscience enters the sentence, the conversation ends. Nobody in the room can refute it, so everybody accepts it. That is why I wrote, on each of the 38 concepts here, how much it was actually measured. And that suspicion brings a question along with it, more uncomfortable still: measured in whom? The answer starts on the slow side of the story, with what can be proven about a brain that has not changed.
How this is known: bone survives
Saying the brain is the same as it was three hundred thousand years ago is easy, and it is the opening line of every bad course in applied neuroscience. It is worth showing where it comes from, and worth showing where the claim stops.
The ear, at least 430,000 years ago
The fossilised ossicles of five individuals from Atapuerca allowed sound transmission through the outer and middle ear to be reconstructed, and it already followed the human pattern in the mid range of speech, 2 to 4 kHz, and not the chimpanzee’s (MartínezMeasured the inner ear of 350,000-year-old fossils and showed that the human hearing range was already ours.One reference in this work:2004Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in SpainSee in the bibliography → et al., 2004). In the 3.5 to 5 kHz range they were not modern yet, and the ones who get there are the Neanderthals (Conde-ValverdeOne reference in this work:2021Neanderthals and Homo sapiens had similar auditory and speech capacitiesSee in the bibliography → et al., 2021). The fossils were re-dated after publication and are at least 430,000 years old, older than our own species.
The size, 300,000 years ago — the shape, much later
The braincase of Homo sapiens was already within today’s range three hundred thousand years ago. The shape was not: the globular brain we have now emerged gradually, and only reached its modern form far later (NeubauerCompared fossil skulls and showed that brain size reached today’s long before its shape did, globularity is recent.One reference in this work:2018The evolution of modern human brain shapeSee in the bibliography →, Hublin and Gunz, 2018). It is the most honest caveat I managed to make, and it is the whole argument in miniature. The engine is old, what it became is less so, and nothing I teach here depends on that difference being zero.
This is the ruler here. Where the evidence holds, it shows; where it ends, it says so.
Where the tension comes from
The tension between the two speeds is not new, but it tightened for good in 2020. The pandemic accelerated the shift to digital everywhere, and in Brazil the share of people aged ten or over using the internet rose from 78.3% in 2019 to 90.5% in 2025, the first time the country passed 90%, according to the 2021 and 2026 editions of PNAD Contínua, the IBGE household survey. Under pressure, companies multiplied digital products, and job posts began demanding people who could start fast.
To meet that demand, bootcamps lasting a few months became the most visible way into the profession. HolonIQ estimated in 2022 that intensive digital-skills programmes had trained more than 100,000 people in 2021, and projected more than 380,000 graduates a year by 2025; the Course Report directory listed, in 2026, more than 900 active bootcamps. Sold as “from zero to hired in a few months”, these courses teach checklists, the Design Sprint, the Double Diamond, the interface kits, and leave little room for attention, cognitive load or memory, which was exactly the criticism Jared SpoolArgued, in a 2025 talk, for UX’s return to the investigative method. It is the talk that gives the manifesto’s argument its name.One reference in this work:2025UX: o retorno ao design investigativoSee in the bibliography → made in 2025.
The result is a training that teaches the checklist and almost never teaches how to say, in terms of attention, cognitive load or memory, what an interface does to the person using it. I have nothing against the shortcut; in a fast world it is valuable. What is missing is the judgement to know when it is charging the person who uses it, and that is what I try to give back.
The hypothesis this work tests
Designing effective digital realities requires understanding how the brain builds each person’s reality out of the senses, the instincts and the three kinds of memory AtkinsonOne reference in this work:1968(org.)See in the bibliography → and Shiffrin separated in 1968, the sensory, the working (in the model Alan Alan BaddeleyFormulated the model of working memory this site uses as its base, the phonological loop, the visuospatial sketchpad and the central executive.One reference in this work:2003Working memory: looking back and looking forwardSee on Wikipedia ↗See in the bibliography → revised in 2003) and the long-term. And it requires recognising that it builds with what it receives: the same mechanism, fed by another place, another history and another day, gives back something else. Frameworks and artificial intelligences are means, not ends; respecting the singularity of the person who uses something requires knowing both the mechanism and the context, and neither is updated when the tool changes.