Infants respond to people and objects in the same way
Babies can cry for attention and by 6 weeks old they are starting to smile but they may well smile at a range of people, not just the primary caregiver
Babies do, however, show a preference for looking at images of faces and eyes (Fantz 1961)
Weaknesses of Schaffer & Emerson's stages of attachment
Not all children will fit neatly into the stages: some children may bond quickly with a range of people while others may be slower, so the theory lacks some reliability
It is notoriously difficult to measure and track infant behaviour: many aspects of attachment remain a mystery i.e. a baby cannot explain how they are feeling or give reasons for their actions