What’s Human State Interface ?

Photo by Joshua Reddekopp on Unsplash

Software understands files, networks, locations, and time.

But it still lacks a native way to understand human state.

“As we step into the year ahead, we’re thinking about how systems can better understand and adapt to the humans using them.”

So we said New Year New Interface for humans and we’ve introduced the first Human State Interface (HSI 1.0) — a foundational interface specification for representing human physiological, cognitive, and behavioral state in a structured, interoperable, and privacy-preserving way.

HSI 1.0 is the first step toward making human state a first-class primitive in modern computing.

The Missing Layer in Computing

Modern systems are excellent at handling what users do — clicks, requests, transactions, locations.

They struggle with how users are doing.

Stress, focus, calm, fatigue, overload, regulation — these states shape behavior, performance, and outcomes, yet they remain invisible to software systems.

Historically, attempts to model human state have faced three major problems:

1. Tight coupling to devices (one wearable, one SDK, one platform)
2. Privacy risks (raw biosignals sent to the cloud)
3. Lack of interoperability (no shared contract for outputs)

HSI exists to solve these problems at the interface level.

What Is HSI?

HSI (Human State Interface) is a canonical, language-agnostic contract for representing human-state outputs.

Think of it like GPS — not the satellite system, but the coordinate contract.

When someone says “GPS,” you know you’ll receive latitude and longitude in a predictable format.

HSI does the same for human state.

It defines what human-state outputs look like, not how they are computed.

HSI answers questions like:

• How is focus represented?
• How do systems exchange stress or calm signals?
• How are confidence, validity, and time encoded?
• How do different vendors produce comparable outputs?

What HSI Is (and Is Not)

HSI is

• A foundational interface standard
• A contract for human-state outputs
• Platform-agnostic and vendor-neutral
• Designed for on-device, privacy-first computation
• Strictly validated and interoperable

HSI is not

• A wearable SDK
• A biosignal processing algorithm
• A machine learning model
• A cloud analytics system
• A behavioral surveillance tool

HSI deliberately sits between signal processing and application logic.

Human State as Structured Output

HSI represents human state as structured signals, such as:

• Emotional regulation (e.g., calm ↔ stress)
• Cognitive dynamics (e.g., focus, overload)
• Behavioral patterns (e.g., rhythm, fragmentation)
• Confidence and signal quality
• Temporal context (windows, sessions, transitions)

Importantly, HSI never contains raw biosignals like ECG, PPG, or interaction content.

Only interpreted state representations are exposed.

This keeps the interface expressive while preserving user privacy.

Privacy by Design

Figure: The Human State Interface (HSI) 1.0 execution boundary.

Raw physiological and behavioral signals are processed locally within an on-device privacy boundary, transformed into internal human state representations (HSV), and optionally exported through HSI 1.0 as structured, interoperable outputs for external systems.

Privacy is not an add-on in HSI — it’s structural.

HSI assumes:

• Computation happens locally, on-device
• Raw biosignals never leave the user’s device
• Outputs are abstracted, bounded, and validated
• Consumers of HSI cannot reverse-engineer raw data

By standardizing outputs instead of inputs, HSI prevents over-collection and misuse by default.

Why HSI 1.0 Matters

HSI 1.0 enables something new:

• Applications that adapt to human state without spying
• Research systems that compare results across devices
• Developers who can build once and run across ecosystems
• A shared language between neuroscience, HCI, and software engineering

It creates a clean separation of concerns:

• Signal acquisition → device-specific
• State inference → model-specific
• State exchange → standardized (HSI)

This separation is what allows ecosystems to scale.

Who Is HSI For?

HSI 1.0 is designed for:

• Developers building human-centered applications
• Researchers working on affective computing or HCI
• Product teams exploring adaptive interfaces
• Platform builders designing next-generation OS or SDK layers

It’s an early, developer- and research-first release — intentionally minimal, stable, and extensible.

The Road Ahead

HSI 1.0 is just the beginning.

Future versions will expand:

• State taxonomies
• Temporal semantics
• Cross-session continuity
• Validation and benchmarking tools
• Governance and RFC processes

But the core principle will remain the same:

Human state should be computable, interoperable, and private by default.

Closing

For decades, software has adapted humans to machines.

HSI is about enabling machines to adapt — responsibly — to humans.

HSI 1.0 introduces a shared interface for human state, making it possible to build systems that are not just intelligent, but human-aware.

If you’re building in this space, we’d love your feedback.

HSI 1.0 is part of the Synheart project, an open effort to build privacy-preserving human-state infrastructure for modern systems.

HSI 1.0 is an early step toward that future.

💜 Don’t forget to drink water, and stay connected with your state. 💜