Day 16 of 150 Speed Difficulty 8/10
Vigilance collapses after about thirty minutes of monitoring
Quick answer
Vigilance collapses after about thirty minutes of monitoring. Today's question (Vigilance decrement) asks about a finding from Mackworth, N. H. in 1948. The correct option is Drops sharply after about 30 minutes — full explanation, primary source, and glossary cross-links below.
Today's question
Mackworth's "Clock Test" (1948) showed that sustained-attention performance:
Reveal the answer and explanation
Correct: B — Drops sharply after about 30 minutes
Mackworth, working with the Royal Air Force on radar-operator performance, set participants to monitor a clock hand for occasional erratic jumps. Detection rates collapsed after roughly 30 minutes — the canonical "vigilance decrement." The finding shaped shift design in safety-critical roles and remains the benchmark paradigm for sustained-attention research and the cognitive-fatigue literature.
About the source
Mackworth, N. H. (1948). The breakdown of vigilance during prolonged visual search. Quarterly Journal of Experimental Psychology, 1(1), 6–21.
Every Cognition Bible question cites a primary source — a paper, book chapter, or monograph that exists, that we can point to on Google Scholar, and whose finding the question accurately summarizes. No fabricated authority strings, no name-drops without paper-level grounding.
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