The Fourth Hemisphere: Marketing for AI

Your buyers ask AI before they ask you. We shape what it says.

ChatGPT, Claude, Gemini, Copilot, and Perplexity now sit between your company and the people deciding whether to buy from it, invest in it, or cover it. The Fourth Hemisphere: Marketing for AI is Third Hemisphere's practice for that layer. We measure how the five major AI engines represent your brand, then build the earned media, structured content, and entity consistency that change the answer.

The human brain has two hemispheres. Third Hemisphere has always been the third: the capability that sits alongside a company's own thinking and gives it higher-level language, intelligence, influence, and reach. A fourth hemisphere now exists: AI. Buyers, investors, journalists, and regulators ask this layer what to think before they form their own view. It reads everything, remembers selectively, and answers with confidence. Most companies have never checked what it says about them.

The Fourth Hemisphere works in both directions. We market with AI: audit tooling that measures how brands appear across the five major engines, AI-assisted research, content systems, and reputation monitoring, so every engagement carries the compounding speed and rigour of the layer itself. And we market to AI: we treat the engines as an audience in their own right, building the earned media they cite, the structured content they can retrieve, and the entity consistency they can trust.

Every engagement starts with The Fourth Hemisphere Audit. We ask the five major AI engines 50 real questions your buyers ask, then score your brand with our PACT methodology across Presence, Authority, Consensus, and Truth. You see exactly where you appear, where a competitor holds your slot, and what it will take to change the answer. From there, a 6 to 12 month programme of earned media, AI-ready content, and entity work moves the score, with quarterly re-audits proving the shift.

The Fourth Hemisphere Audit: 50 buyer questions across five AI engines
PACT scoring across Presence, Authority, Consensus, and Truth
Earned media programmes built for AI-engine citation
Structured, AI-ready content and entity consistency work
Leadership workshops on AI visibility for in-house teams
Quarterly re-audits that measure movement in the answers themselves

Our Marketing for AI Approach

Audit We ask the five major AI engines, ChatGPT, Claude, Gemini, Copilot, and Perplexity, 50 real questions your buyers ask, and record every answer, citation, and omission.
PACT Score Each answer is scored across Presence, Authority, Consensus, and Truth, producing a single benchmark for how strongly and accurately your brand appears in AI-generated answers.
Gap Analysis We show where you are absent, where a competitor holds your slot, which sources the engines rely on, and which inaccuracies need correcting.
Programme A 6 to 12 month programme of earned media the engines cite, structured content they can retrieve, and entity consistency they can trust, prioritised by commercial impact.
Re-audit & Monitoring Quarterly re-audits track the PACT score and the answers themselves, so you can see representation improving engine by engine, question by question.

What is marketing for AI?

Marketing for AI is the practice of making a company discoverable and accurately represented in answers generated by AI engines such as ChatGPT, Gemini, Claude, Copilot, and Perplexity. It combines authoritative structured content, entity consistency, and earned media that AI engines cite.

How is this different from SEO?

Search optimisation targets ranked links. The Fourth Hemisphere targets the answer itself: what AI engines say, recommend, and cite when asked about your category. The two disciplines are complementary, but the work, the measurement, and the sources that count are different.

What is the PACT methodology?

PACT scores how a brand appears across AI engines on four dimensions: Presence (do you appear at all), Authority (are you positioned as credible), Consensus (do the engines agree about you), and Truth (is what they say accurate). The audit produces a benchmark score and a question-level record behind it.

What does The Fourth Hemisphere Audit involve?

We ask the five major AI engines 50 real questions your buyers ask, record every answer and citation, and score the results with the PACT methodology. You receive the score, the evidence behind it, and a prioritised plan for improving the answers.

What does it cost?

The audit is a fixed-fee engagement, and programmes are scoped from the audit's findings. Book a discovery call and we will confirm pricing for your category and markets.

How long before AI-engine answers change?

Engines refresh their retrieval sources continuously but reweight authority over months, so programmes run 6 to 12 months with quarterly re-audits. Some corrections, such as fixing inaccurate entity data, can move answers faster than building presence from zero.