Theory 54/Yawning/Ratio lens
Frequency Is Arousal Against Sleep
The claim
Yawn frequency is set by the ratio of arousal to sleep pressure, peaking where the two are both moderate rather than at either extreme.
01Mechanism
Yawning regulates state transitions; it is triggered when the animal is neither fully alert nor asleep.
02Prediction
Frequency should peak at an intermediate ratio.
03Refutation
Frequency increasing with sleep pressure would remove arousal.