Smell, the Last Sense AI Still Lacks

Opening

Hello, dear subscriber, this is Oz’s Knowledge Talking. Do you happen to like perfume?

Let me start with something a bit unusual today. We’re living in an era where AI passes medical and bar exams, AI-designed cancer drugs enter clinical trials, and AI agents sort our email for us. But an article I recently read in Noema magazine raised an interesting question.

“Why is research on giving AI a sense of smell moving so slowly?”

Let me give you one number first. Between 2015 and 2025 — a full 10 years — the number of papers on machine olfaction¹ came to less than 1% of the papers on computer vision and natural language processing combined. Major AI conferences like NeurIPS, ICLR, and ICML barely touch the topic. Even most of the humanoid robot startups flooding the market today are designing their machines without any olfactory sensors at all.

This might look like a simple matter of priorities — “vision and language first, smell later.” But the reason I’m bringing this up today is that I don’t think this is a question of sequence at all. I think it’s a question of structure. Let’s unpack what that structure actually is.

Overhyped Headlines and the Real Gap

The phrase “AI that can smell” isn’t new. Headlines like “Computers Are Learning to Smell” (The Atlantic) and “AI is digitizing our sense of smell” (World Economic Forum) have been recycled for years. But the Noema article points out that most of these headlines are overstated. Take a close look at the BBC Future piece “An AI started ‘tasting’ colours and shapes”: what actually happened is that the LLM simply repeated the human associations baked into its training data — “sweet things are pink and round.” The AI didn’t smell anything; it copy-pasted text that humans had already written about smell. In other words, it didn’t “smell” anything — it merely described smell.

So why does this matter now? As discussions of “LLMs hitting a ceiling” have gained traction, AI researchers have started looking to world models² — systems that internally reconstruct the structure of the world using multiple sensory channels like vision, hearing, and touch — as the next breakthrough. And by volume of daily sensory input, smell ranks third for humans, right after sight and hearing. Yet most world-model research leaves this third channel out entirely.