Why the back half of a survey gets straight-line answers

A market-research firm analysed thirty thousand completed surveys. Response variance — a measure of discriminating thought — dropped by thirty-four percent between the first and second halves. In the final quarter, respondents selected the same scale point on consecutive items sixty-one percent of the time. The data was collected; its second half was noise.

What everyone sees

Respondents believe they answered honestly throughout. They do not notice the decline in their own discrimination. The straightlining feels effortless because it is — which is precisely the problem. The ease is a symptom of depletion, not of consistent opinion.

What is actually happening

Krosnick’s satisficing theory shows that as cognitive resources deplete, respondents shift from optimising (choosing the best answer) to satisficing (choosing an acceptable answer with minimal effort). Straightlining — selecting the same response category repeatedly — is the most extreme form of satisficing. It produces data that looks complete but carries no signal, because the respondent is no longer evaluating each item independently.

Why it stays hidden

Straightlining hides because surveys look finished. Every question has an answer, and completion rates are high. The depletion is invisible in the response data until variance analysis reveals it. Researchers who trust completion rates over variance metrics are reading noise as signal.