2.3.2. Behavioral state
The behavioral state was measured to examine how the interventions affected preterm infant’s behavior using the Anderson Behavior State Scale (ABSS) (Anderson et al., 1990). This scale determines the behavioral state of an infant based on observations of respiratory regularity, opening or closing of the eyes, limb and trunk activity, and the intensity of crying. This study classified behavioral states into three stages (sleep, awake, and fussy) according to ABSS. The TRNs assessed the behavioral state at 10 min before intervention, 3 times during the 15-minute intervention period (at the 5th, 10th, and 15th min), and 10 min after each intervention (i.e., Yakson and 30 GHT treatments). At each time point, the behavioral state was evaluated for
1 min, from 30 s before to 30 s after the designated time point