Vocalizes pleasure and displeasure¹⁴

Grunts, growls, or complains¹⁴

Gurgles with pleasure, squeals with excitement, giggles, belly laughs¹⁴

Smiles at mirror image¹⁴

Turns when hears name¹⁴

Tries to imitate facial expression¹⁴

Disturbed by strangers¹⁴

Distinguishes adults from children¹⁴

Smiles at and reaches out to pat strange children¹⁴

Calls parents for help¹⁴