a. Activity level: Some infants are very active from the time of birth, whereas others may be, for the most part, passive or quiet.

b. Sensitivity: Infants may demonstrate individual preferences for stimulation of their senses: for example, some may respond consistently to touching whereas others may be more responsive to singing.

c. Self-stimulation: Some infants may engage in constant mouth activity (e.g., sucking, hands in mouth).

d. Patterns of sleep/waking/feeding: Some babies develop regular patterns, and others may be more unpredictable.