People finish the task and still can’t explain what happened. I call that gap cognitive distance. I measure it, write about it, and build products that close it.
The idea
Cognitive distance is the degree of mismatch between the conceptual structure that a system requires for correct interpretation and the mental model that a user actually constructs.
This switch is the variable in my study: the same sentence, two registers.
The map
Most metrics measure effort. A task can be effortless and still misunderstood. That corner is where products quietly fail.
The line of work
One idea, carried all the way through: named, measured, tested, built and run in production. Tap a red dot to see where a number comes from.
01 Theory
118 pagesReceipt118 pagesLength of the bookMethodPage count of the free online edition and PDF.Sourcebook.izaias.xyzChecked, 13 chaptersReceipt13 chaptersChapters in the bookMethodCounted from the table of contents.Sourcebook.izaias.xyz/readChecked, 66 cited worksReceipt66 cited worksReference listMethodCounted from the references page.Sourcebook.izaias.xyz/read/referencesChecked. Free to read.
02 Instrument
A 0 to 100 scoreReceipt0 to 100Cognitive Distance Index scaleMethodDefined in the CDI manuscript: four dimensions combined into one score.SourceUsers Complete Tasks but Still Cannot Explain Why (manuscript, 2026)Checked across four dimensions of understanding.
03 Experiment
Three tasks, three languagesReceiptthree tasks, three languagesEveryday Services Study designMethodBank transfer, medical appointment and licence renewal, in English, Spanish and Portuguese.Sourceeverydayservices.studyChecked. Only the wording changes.
04 Product
Queues people can leave, and images that never get uploaded. 3.6 KB gzippedReceipt3.6 KBcompresso.js, gzipped coreMethodGzipped size of the published library build.Sourcecompresso READMEChecked.
05 Infrastructure
Live TV at 3 to 6 s latencyReceipt3 to 6 sLive TV latencyMethodStated in the case study for the OBS to nginx to HLS pipeline.SourceRádio Alvorada TV case study (design.izaias.xyz)Checked, $0 origin cost for audioReceipt$0Audio origin costMethodSelf-hosted Icecast and WebSocket on an always-free cloud tier.SourceRádio Alvorada TV case study (design.izaias.xyz)Checked.
Case files
Products
Queue management that lets people choose how they wait, and switch without losing their place.
4 roundsReceipt4 rounds“Brutal review” roundsMethodDocumented review rounds in the product repository.SourceVia repository docsChecked documented review rounds before the pilot
Products
The theory turned into a tool. Compress, resize and convert images in the browser. Nothing is uploaded.
3.6 KBReceipt3.6 KBcompresso.js, gzipped coreMethodGzipped size of the published library build.Sourcecompresso READMEChecked gzipped core library
Client work
A workflow designer for enterprise contract lifecycle management, with visual diffs people actually read.
70% fasterReceipt70% fasterAudit cycle timeMethodAudits went from days to hours after the visual diff shipped.SourceRésumé fact baseChecked faster audit cycles
Systems
Design system, website, a browser based broadcasting tool and live TV for a Brazilian broadcaster.
3 to 6 sReceipt3 to 6 sLive TV latencyMethodStated in the case study for the OBS to nginx to HLS pipeline.SourceRádio Alvorada TV case study (design.izaias.xyz)Checked live TV latency
Laws
Easy isn’t the same as understood.
from the book
The reason before the thing.
from Aurora
No surface ships before its write path.
Every claim here is one the product can keep today.
Measure before you claim.
from Via and Compresso
From the notebook
Cognitive distance is the degree of mismatch between the conceptual structure that a system requires for correct interpretation and the mental model that a user actually constructs. The term was coined by Izaias Cavalcanti, who measures it with the Cognitive Distance Index (CDI).
Cognitive load is how much effort a task takes. Cognitive distance is how far a person’s understanding is from how the system really works. They are independent: a task can be easy and still misunderstood, which Izaias Cavalcanti calls “easy but opaque”.
Izaias Cavalcanti is a Brazilian product designer, researcher and design engineer who coined the term cognitive distance. Izaias wrote the book From Cognitive Load to Cognitive Distance, created the Cognitive Distance Index, runs the Everyday Services Study, and builds products such as Via and Compresso.
With the Cognitive Distance Index (CDI), a 0 to 100 score across four dimensions: perceived understanding, predictive accuracy, interaction confidence and conceptual transparency. Scores fall into four bands, from strong alignment (0 to 25) to serious misalignment (66 to 100).
Through the invitation form at portfolio.izaias.xyz/invite, or by email. Invitations welcome include talks, research partnerships, international collaborations, special projects, and Senior, Staff or Lead roles in product design and design engineering, remote or with relocation.
Invitations
It’s in São Paulo.
Free online and as a PDF. 118 pages, 13 chapters.
About 15 minutes, three everyday tasks, in English, Spanish or Portuguese. Anonymous.
APA, MLA, Chicago and BibTeX, ready to copy.
Conferences, universities, teams and public institutions. Tell me the audience and the date.
Replications, field studies, translations of the instrument, joint papers.
Cross border projects, public service work, labs and studios. Remote by default.
Special projects, and Senior, Staff or Lead roles in product design and design engineering, remote or with relocation.