Hello, fellas. In this session we will learn the use of verbs of perception. Verbs of perception express the experience of one of the physical senses. They are also called perception verbs or perceptual verbs.
Several of them are followed by the simple form of a verb (the infinitive form without to) or the -ing form (the present participle).
The two forms often carry little difference in meaning, except that the –ing form frequently gives the notion of while.
1) He saw his friend ride a bicycle.
2) He saw his friend riding a bicycle. (He saw his friend while he was riding a bicycle)
Sometimes, the use of –ing form means that an activity is already in progress when it is perceived.
1) When she walked into her boarding house, she heard her roommate crying. (The crying was in progress when she first heard it)
2) When she walked into her boarding house, she heard her roommate cry. (She heard the crying from beginning to end)
ThoughtCo., Verb of Perception, https://www.thoughtco.com/verb-of-perception-1692486
Betty Schrampfer Azar, Understanding and Using English Grammar: Third Edition