Final answer:
If the screen drops and there are three objects instead of the two the infant saw, the infant is likely to show surprise, which demonstrates their development of object permanence and expectancy of consistent environmental events.
Step-by-step explanation:
An infant sees an object get hidden behind a screen, then a second object be placed behind the screen. If the screen drops and there are three objects, instead of the two the infant saw, he will likely show surprise or attention because this scenario challenges their object permanence understanding. Object permanence is a cognitive milestone in the sensorimotor stage of development, where infants recognize that objects continue to exist even when they cannot be seen, heard, or touched. According to studies, when infants develop object permanence, they expect consistency in their environment. Between 5 and 8 months, infants develop object permanence and would look for objects they have seen being hidden, as they remember them. If infants witness more objects than expected, like in this example with three objects instead of two, they would likely react, indicating their ability to track the objects and recognize discrepancies in their environment.