Indicators of infant's social and emotional competence during the first 12 months of life include:
By 3 months:
attends and responds to caregiver's face and voice;
quiets when talked to, picked up or held;
responds positively to comfort and shows capacity to calm itself and relax;
smiles spontaneously at people in home;
communicates excitement and distress;
makes eye contact and sustains gaze.
By 6 months:
communicates pleasure and protest;
exhibits many interactive behaviours - smiles, vocalises, laughs, imitates and responds to name;
prefers one or two caregivers to others;
shows strong interest in people and things;
is attentive and responsive.
By 9 months:
imitates interactions with people and things;
identifies mother/father as primary attachment figure or has attachment to caregivers;
is able to play interactive games "bye-bye" or "peek-a-boo";
approaches/follows mother/father/caregiver as primary attachment figures;
shows distress when separated from mother/father;
is wary of strangers.
By 12 months:
expresses a range of feelings - happiness, anger, sorrow and frustration - and recognises them in others;
understands mother/father as primary care-giving figures who will nurture, and has established a special attachment to primary substitute caregiver(s).
As described by Dr Deborah Weatherston, director of infant mental health at Merrill-Palmer Institute, Wayne State University, Detroit, Michigan, US.