A new Semrush study, conducted with Kevin Indig and Growth Memo, examined whether topical authority in one category carries over into related ones in ChatGPT. Analyzing data from the Semrush AI Visibility Toolkit, the dataset covers 1,094 US categories tracked monthly in ChatGPT from January through June 2026, with five prompt variants per category. It includes 283,215 domain-category citation observations and 76,493 brand-mention observations across January through May, plus 45,578 category-expansion appearances by 1,458 mapped brand entities. The study tracked two signals separately: citations, which are sources ChatGPT links to as evidence, and brand mentions, which are brand names included directly in the response text. Among the brands analyzed, citations tended to spread more readily across categories than brand mentions did. Getting mentioned by name tended to happen mostly in categories close to a brand’s core expertise, where depth mattered more than breadth. Brands that consistently appeared across a category’s prompts were associated with successful expansion into new categories, while showing up once in 20 categories didn’t build a higher brand-mention share. Industry shaped the pattern: finance and real estate saw broader coverage associated with more citations, while legal and healthcare set a higher bar where full prompt coverage and repeat citations didn’t reliably translate into brand-mention share. Topical authority gave brands a stronger starting point for adjacent categories, not unrelated ones.