Developers using AI felt 24% faster
They were 19% slower
METR 2025 — n=16 experienced developers, mature codebases
You spend less time writing, more time checking. The AI writes fast. Finding bugs in plausible-but-wrong code is slow.
What makes collaboration work
Blaurock et al. analyzed 106 studies asking: what makes AI collaboration work? Three factors showed strong effects:
"Show your work. Let them steer. Don't interrupt with questions."
— Synthesized from Blaurock et al. (2024), Journal of Service Research
Cognitive extensions
Clark & Chalmers (1998), "The Extended Mind"
If we call Inga's process "remembering," we should call Otto's the same.
The notebook is part of Otto's mind.
The parity principle: If a process were done in the head, we'd call it cognition. When external but functionally equivalent, it's cognitive extension.
This is why we call them cognitive extensions, not tools.
The question isn't "is AI helpful?" but "what kind of mind are you building?"
Three ways AI extends capability
Complementary
Constitutive
Substitutive
The distinction isn't what task you're doing.
It's how you're doing it.
Proof: Design determines outcome
Harvard researchers gave students the same AI tutor. The only difference was how it was designed.
Same AI. Same students. Design made the difference.
Bastani et al. (2025), PNAS — randomized controlled trial, n=1,000+
Why these factors matter
Why do transparency and control matter? One study found a mechanism.
Students who treated AI as a learning tool — something to question and learn from — maintained critical thinking. Students who treated it as an answer machine didn't. The difference: 35.7x more likely to stay sharp.
This comes from ACU Research Bank — not a top journal yet. But the 35.7x effect is huge, and it matches what validated studies predict. Treat as suggestive, not proven.
Your mindset may matter more than the model.
| Orientation | Behavior | Outcome |
|---|---|---|
| Mastery | Views AI as scaffold, questions output | Protected |
| Performance | Views AI as oracle, accepts output | At risk |
ACU Research Bank (2025) — effect requires replication
Design principles
These principles guide how we build cognitive extensions.
- 01
Collaborative agency
Both human and AI retain agency. You see the reasoning. You can redirect. You stay in control.
- 02
Bidirectional learning
The human grows, not just consumes. Each interaction leaves you more capable, not more dependent.
- 03
Transparent abstractions
Extensions are readable text, not black boxes. You can fork them, modify them, understand them.
- 04
Compounding value
Each solution makes the next one easier. What you learn today becomes a foundation for tomorrow.
Foundations compound
Every interaction either builds capability or erodes it. Small differences compound.
These extensions are designed for the upper path.