Answer:2. preferential looking
Explanation:
Based on American Psychological Association, the preferential looking technique is a technique that is used to test the visual capability of those who can't use words or who rely on nonverbal communication.
Such as infants or animals , it tests whether infants are capable of distinguishing between different stimuli for example if they state at the picture of their parents more than they do with a picture of a stranger that means they can discriminate different stimuli. This can means their perceptual system is developing well.