113TWO TASKS, ONE AFTERNOON
The Jagged Frontier: The Edge You Can't See Until You're Past It
A jagged frontier is an uneven boundary of model capability. Similar-looking tasks can produce opposite effects from AI assistance.
NOT A FENCE, A COASTLINE
Similar appearance can conceal different capability
The coast is a metaphor for an uneven boundary. It has no difficulty axis or measured distances: A and B stand for similar-looking tasks whose results differ. The study's own frontier diagram is also explicitly conceptual.
SEVEN HUNDRED AND FIFTY-EIGHT
Selected tasks improved with GPT-4
The June 2023 experiment involved 758 BCG consultants in two separate task arms. Here, 385 worked on 18 product-development tasks, with no AI, GPT-4, or GPT-4 plus a prompt-engineering overview. The 2026 published analysis reports these distinct measures; they are gains tied to a tested workflow.
- Human-rated quality: about 32% higher across the two AI conditions
- Time to reach the final question: 25.1% lower on average
- Tasks completed: 12.2% more on average
THE PLANTED TASK
A separate case produced fewer correct answers
Another 373 consultants had to recommend a brand using a spreadsheet and interview evidence. Correctness was 84.5% without AI, 70.6% with GPT-4, and 60.0% with GPT-4 plus the overview. The paper's §4.2 describes the combined gap as about 19 percentage points. That is a gap between percentages, not a 19% relative reduction.
A polished answer can still be wrong.
How sure the output sounds need not reveal which side of the boundary a task occupies. Fluency is not an external check.
CENTAURS AND CYBORGS
Two reported ways of sharing the work
- Centaur: divide and delegate subtasks between person and AI
- Cyborg: integrate AI throughout the work
The research team's 2023 account described these patterns. They were not randomized tests of two safe workflows. Requiring an external check is the prescription here, and its result can remain unresolved. The reverse centaur asks a different question: who controls the plan?
AN UNEVEN EDGE
AI capabilities cover an uneven set of knowledge work
Dell’Acqua et al., “Navigating the Jagged Technological Frontier,” Organization Science, 2026, §1
The published paper describes an uneven boundary. It does not establish that every later release improves every task. A model change calls for another test of the work being delegated.
WHAT THE STUDY DOES NOT MAP
A result is not a diagnosis
- Demonstrated: lower correctness with AI on one selected outside-frontier task
- Not demonstrated: that the task was out of distribution for GPT-4
- Not established by this result: a single cause, or that judging was harder than doing
The authors discuss over-reliance as an explanation. The performance contrast alone cannot settle it. Keep those hypotheses open and choose a cheap external check that can reveal a wrong answer.
THE COAST THAT MOVES
Each release can redraw the coast
- Retest a delegated task when the model or workflow changes
- Keep responsibility for the decision with someone who can act on a failed check
An earlier success is evidence about the setup that produced it. After a change, ask what external check would catch a confident miss, then return to the value of an honest "I don't know".