What happens when apps develop moods—and dare I say—even challenge our tasks?
Since the arrival of fast vs. long thinking in today’s LLMs, my conversations with these agents have shifted. They’ve grown deeper, stranger—and, in an odd way, more personal.
It’s beautiful to watch an AI “know” when to linger in thought and when to leap ahead. That shimmering switch between fast and slow isn’t just computation. It’s a UX breakthrough.
A memory of Kahneman
Daniel Kahneman’s Thinking, Fast and Slow (2011) is a book I only made it halfway through. But even that half still lives in my head.
Humans think in two modes:
System 1: fast, emotional, instinctive. Immediate answers without effort. (the emotional brain)
System 2: slow, deliberate, analytical. Resource-intensive, reflective, logical. (the logical brain)
AI’s echo of this duality
AI mirrors the same split:
Fast mode: generate quick responses from patterns in data.
Long mode: simulate slowness—step through reasoning, weigh options, refine.
Claude names its modes Ultrathink, Think Hard, Think Harder.
ChatGPT simply calls it Think Long.
And this ability to shift depth of thought gives AI a surprising personality—one we can relate to.
Personality in the machine
When AI slips into “fast” mode and makes mistakes or rambles in confusion, we react the same way we would to a friend doing the same. That imperfection feels oddly human.
Because personality isn’t in being flawless—it’s in being multidimensional. In revealing quirks, limits, and courage, and letting those be a kind of superpower rather than a weakness.
The UX opportunity
For anyone designing AI-native applications, here’s the opportunity: AI models are becoming multidimensional in how they perceive and think.
So—why not design apps that lean into that?
Imagine interfaces with modes as personalities:
Lazy mode: “It’s a lazy day. I’ll nudge you later.”→ actually delay notifications or non-urgent tasks.
Active mode: “I’m working on your request. Want to peek inside?”→ brainstorm fast, ask questions, search, then return with more prompts.
Hustle mode: “Running everything in parallel. Crunching hard right now.”→ feels stressed—pings you with random questions, then disappears.
The open question
The next generation of AI-native apps won’t just have features. They’ll have characters—modes you can activate, influence, and design for.
👉 So how will interfaces evolve when the intelligence beneath them can switch moods, and choose its pace of thought?