Final answer:
6- or 7-month-old infants show that they can distinguish between the deep and shallow sides, indicating an understanding of depth and potential risk.
Step-by-step explanation:
In the study of infant depth perception using the visual cliff apparatus, 6- or 7-month-old infants tend to stop at the drop-off. This shows that they can discriminate between the deep side and the shallow side and that they are aware that the deep side can be dangerous. By this age, infants have significantly improved in their physical and cognitive development. Their vision is nearly as acute as adult vision, and they have started to show the ability to discriminate depth. This milestone in development is crucial as it demonstrates not only their sensory abilities but also their cognitive growth in understanding the potential risk associated with the deep side of the visual cliff, aligning with Piaget's sensorimotor stage.