Theory Card 070 — Mental Simulation / Check
Research lens
Mental simulation is the ability to run the solution in your head or on paper before trusting it. In the Check stage of BASIC, the goal is to verify correctness, quality, and risk. That makes this concept especially relevant here, because it shapes how much mental work the candidate is trying to carry at once and what gets made explicit.
Why it matters in SWE interviews
Good candidates dry-run recursion, pointer movement, queue flow, and failure paths instead of waiting for bugs to reveal themselves. Check formalizes mental simulation so it happens consistently instead of only when time happens to remain. In practice, Check is where the candidate should ask: Does the answer actually satisfy the prompt, handle edge cases, and survive scrutiny? That question acts like a cognitive boundary. It protects the answer from turning into an unstructured search.
BASIC move
A strong move here is to review and stress-test before you hand the answer over. For Mental Simulation, that means deliberately naming the important units instead of juggling them implicitly. The interviewer sees cleaner reasoning, and the candidate benefits from creates a verification loop instead of assuming success.
Common miss
The miss is assuming an answer is correct because it looks elegant. When that happens, the candidate usually feels busy, but the answer is actually becoming less inspectable.
Practice prompt
“While practicing, pause at the Check step and explain how Mental Simulation changes the way you would handle the prompt.”