Which Cue Most Likely Functions as Sign Stimuli to Trigger

Question

Which cue most likely functions as sign stimuli to trigger smiling in very young babies?
A) the presence of two eyes
B) a detailed likeness of any person's face
C) a detailed likeness of one of the baby's caregivers
D) the outline of the smiling mouth

Accepted Answer

The presence of two eyes is a simple visual cue that can trigger smiling in very young babies, as it is a basic feature they respond to even before they can recognize specific faces or expressions.