Impact of Sleep Extension and Restriction on Children's Emotional Lability and Impulsivity

34 typically developing children aged 7-11

Healthy children aged 7-11 with no reported sleep, behavioural, medical, or academic problems

Randomized parallel-group experimental manipulation adding or removing one hour of weekday sleep relative to habitual duration. Genuine randomization and, importantly, teacher-rated outcomes with teachers blinded to sleep condition. But n = 34 is far below the archive's threshold for a well-powered trial, the achieved manipulation was much smaller than intended (27 min extension, 54 min restriction), and the outcome is a behaviour rating scale rather than achievement.

A cumulative sleep extension of 27.36 minutes produced detectable improvement in Conners' Global Index emotional lability and restless-impulsive scores and a significant reduction in reported daytime sleepiness; a cumulative restriction of 54.04 minutes produced the opposite. The direction and dose are both consistent with the start-time literature, but the effect is on behaviour regulation, not learning.

None internally — randomized allocation. The relevance to the topic is that it supplies the mechanistic bridge (a sleep change of the same magnitude a bell-time delay produces does move behaviour) without supplying any achievement evidence.