Fitts’s Law is one of those design principles everyone learns in school and then quietly stops thinking about. Target size, target distance, movement time. It’s a mouse-and-cursor concept, and once you’ve internalized the basics—make buttons big, put them close—it fades into the background. But with AI and voice becoming primary interaction models, the principle matters again. The friction just moved.
Julian Scaff, writing for Bootcamp, traces Fitts’s Law from desktop GUIs through touch, spatial computing, voice, and neural interfaces. His argument is that the law didn’t become obsolete—it became metaphorical:
With voice interfaces, the notion of physical distance disappears altogether, yet the underlying cognitive pattern persists. When a user says, “Turn off the lights,” there’s no target to touch or point at, but there is still a form of interaction distance, the mental and temporal gap between intention and response. Misrecognition, latency, or unclear feedback increase this gap, introducing friction analogous to a small or distant button.
“Friction analogous to a small or distant button” is a useful way to think about what’s happening with AI interfaces right now. When a user stares at a blank text field and doesn’t know what to type, that’s distance. When an agent misinterprets a prompt and the user has to rephrase three times, that’s a tiny target. The physics changed but the math didn’t.
Scaff extends this into AI and neural interfaces, where the friction gets even harder to see:
Every layer of mediation, from neural decoding errors to AI misinterpretations, adds new forms of interaction friction. The task for designers will be to minimize these invisible distances, not spatial or manual, but semantic and affective, so that the path from intention to effect feels seamless, trustworthy, and humane.
He then describes what he calls a “semantic interface,” one that interprets intent rather than waiting for explicit commands:
A semantic interface understands the why behind a user’s action, interpreting intent through context, language, and behavior rather than waiting for explicit commands. It bridges gaps in understanding by aligning system logic with human mental models, anticipating needs, and communicating in ways that feel natural and legible.
This connects to the current conversation about AI UX. The teams building chatbot-first products are, in Fitts’s terms, forcing users to cross enormous distances with tiny targets. Every blank prompt field with no guidance is a violation of the same principle that tells you to make a button bigger. We’ve known this for seventy years. We’re just ignoring it because the interface looks new.

The shortest path from thought to action
Reassessing Fitts’ Law in the age of multimodal interfaces























