Science1 publisher2 min readPublished
Breathing out sped key presses by 41 milliseconds in a 35-person vigilance test
Northwestern researchers found 35 young adults reacted 41 milliseconds faster to a visual cue while exhaling than while inhaling. That makes breath phase a source of variation in a standard clinical attention test, through a link the team cannot yet explain.
The Scientist · Science desk
What happened
- Responses in the brief pauses between breaths were also quicker than during inhalation, by 21 milliseconds on average.
- Participants did the Psychomotor Vigilance Task, pressing the space bar when a red square turned yellow while a sensor under the nostrils tracked airflow.
- Each participant was tested twice, once before and once after an in-lab daytime nap or an eight-hour overnight sleep.
- The Northwestern-led study was published in the journal iScience.
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Why it matters
- exposure A single PVT score, used clinically to measure sustained attention, varies with which breath phase each cue happened to hit, a factor that has nothing to do with alertness.
- decision Researchers comparing rested and sleep-deprived people on the PVT have to decide whether to record airflow, since a breathing difference between conditions would show up as an attention difference.
- constraint Breath phase was recorded and never controlled, so the 41 ms is an association, and advice to time a race start or a brake to an exhale runs ahead of the evidence.
The team matched thousands of key presses to the airflow waveform recorded at the same moment [13]. Because the cue arrived unexpectedly [10], a participant could not pick which part of the breath it landed in. That design rules out the plainest confound, people timing an exhale to the colour change.
The pause result puts the three phases in order. If the 41 ms exhalation advantage and the 21 ms pause advantage share the same inhalation baseline, exhalation beat the pauses by about 20 ms [1]. Inhaling was slowest and exhaling fastest, with pauses roughly halfway between.
The release does not report the spread around those averages, whether a trial was filed under the breath phase at the cue or at the key press, or whether the gap moved after sleep [5]. The middle point bears on the direction of cause. If phase was read at the press, the breath could be adjusting to the movement.
According to Northwestern, this is the first experiment to track the Psychomotor Vigilance Task continuously across all breathing phases, pauses included [7]. The release frames the stakes with driving, noting that a car at 60 mph covers nearly four feet in 40 milliseconds [11]. The participants were healthy adults aged 18 to 33 [3] at a screen in a lab, so highway braking and older drivers are an extrapolation. "By using a tangible and easy to understand task, we were able to show the relationship between respiration and cognition, which I hope people in a range of fields will find application for," said lead author Erika M. Yamazaki, a former member of Northwestern's Cognitive Neuroscience Laboratory [12].
The explanation is still a hypothesis. "We don't yet know exactly how they are linked, but we suspect neurophysiological efficiency, because other studies have shown that various brain oscillations are synchronized with the rhythms of one's breathing," said senior author Ken Paller, the James Padilla Professor of Psychology at Northwestern [9].
What to watch
- Per-participant results in the iScience paper, showing whether most of the 35 people had a faster exhale or a few individuals drove the average.
- An experiment that paces or instructs breathing and checks whether reaction times move with it, the step from association to cause.
- A replication in people older than 33, the group the release's driving example actually points toward.