The first ninety seconds

Here's a pattern that shows up constantly once you know to look for it: someone knows their material cold, gets asked a question they've genuinely thought about before, and still watches the interviewer's face change in the first minute, because of how it started.

The first ninety seconds of an answer decide how the interviewer listens to the rest of it. If you open strong — a clear claim, a specific number, a decision you actually made — the interviewer leans in and fills in the benefit of the doubt for whatever comes next. If you open by warming up, restating the question, or narrating your thought process out loud (“so, um, I think the way I'd approach this is…”), they start grading everything that follows more skeptically, whether they mean to or not.

It's fundamentally a structural problem: knowing something and describing it out loud, under time pressure, to someone deciding your outcome, are two different skills. You can be excellent at the first and still have never practiced the second.

Why the opening line does so much work

An interviewer forms a working hypothesis about your competence almost immediately, then spends the rest of the answer either confirming or revising it — simply how anyone listens to anything. Your first sentence sets the hypothesis. Everything after it gets filtered through whatever that first sentence implied.

The real fix: front-load the answer. Lead with the actual claim or outcome, then back into how you got there. Compare:

“So this is kind of a tricky one, but I think what I'd probably start by doing is looking at the requirements and then, depending on what I find, maybe consider a few different approaches…”

versus

“I'd cut the timeline in half by shipping the read path first and faking the write path behind a flag. Here's why that ordering matters…”

Same underlying knowledge, in principle. Completely different first impression. The second version front-loads a real, falsifiable claim — which is exactly what an interviewer is listening for, and exactly what most people, under pressure, skip past on the way to explaining their reasoning first.

A rehearsable skill

The honest reason most people don't open strong: they've never said the answer out loud before, under any pressure, to anyone. Reading an answer in your head and producing it live, on the spot, with someone watching, are genuinely different tasks. Reps close the gap.

If you've got a friend who'll ask you hard follow-ups and won't let you retreat into “well it depends,” use them. If you don't — and most people don't, simply a matter of logistics — that's the specific gap a live mock interview is built to close: more reps at saying what you know, live, starting with the answer instead of the runway into it.