The Psychomotor Vigilance Task (PVT) is the gold standard measure of sustained attention and the effects of sleep loss, fatigue, and circadian disruption on alertness. Developed by Dinges & Powell (1985), the task presents a red millisecond counter at unpredictable intervals (2–10 s blank waiting period) and requires participants to press a key as quickly as possible to stop it. The counter then freezes at the reaction time and holds it on screen for one second — the trial-by-trial RT feedback that has been part of the task since the original PVT-192 device and is retained in every validated variant (Dinges & Powell, 1985; Basner & Dinges, 2011; Basner, Mollicone & Dinges, 2011).

The key advantages of the PVT over simple reaction time tasks are:

No practice effect — the lack of cognitive demand means performance doesn't improve over multiple sessions, making it ideal for repeated-measures and longitudinal designs.
High temporal resolution — lapses (RT ≥ 500 ms) are rare in rested adults but increase steeply with sleep deprivation, providing a sensitive index of vigilance degradation.
Portable and valid — the task requires no domain knowledge and minimal instructions, making it suitable for diverse populations.

This implementation uses the brief PVT format (5-minute, ~30 trials) suitable for studies where a 10-minute PVT is impractical. The brief PVT correlates highly (r ≥ 0.85) with the standard 10-minute version on lapse counts (Basner & Dinges, 2011). Researchers can extend to 60+ trials by increasing _main_repetitions.

The response-stimulus interval (RSI) ranges from 2–10 seconds across five evenly spaced levels (2, 4, 6, 8, 10 s), balanced within each 5-trial set so the foreperiod distribution is guaranteed per participant and cannot be predicted. All timing parameters are researcher-adjustable without opening the builder.