Table 2.

GAMM of the association between current sleepiness and the amount of future social activity (in individuals who socialize at least once) at different times of day

Variable	Estimate	SE	t-value	P value
Parametric coefficients
Intercept	0.98	0.01	68.06	<0.001
Workday	−0.18	0.02	−10.61	<0.001
Smooth terms	EDF	RefDF	F-value
Sleepiness	0.99	4	35.19	<0.001
Time of day	2.83	3	71.93	<0.001
Sleepiness × time of day [workday]	5.11	12	5.06	<0.001
Sleepiness × time of day [freeday]	1.95	12	1.07	0.002
Random intercept for participant	228.83	462	1.20	<0.001

GAMM, generalized additive mixed-effect model; EDF, effective degrees of freedom; RefDF, reference degrees of freedom. Smooth terms with categorical moderators, as specified in square brackets, represent separate smoothing terms given the moderator’s condition. An “x” between two variables represents a continuous interaction. All smooth terms are centered at zero. P values for smooth terms represent a test of whether the term is different to a flat line.